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Addition of silver in copper nitride films deposited by reactive magnetron sputtering
Abstract
Silver–copper nitride thin films were deposited on glass substrates by reactive co-sputtering of silver and copper targets. The films were characterized by energy dispersive X-ray spectroscopy to determine the silver to copper atomic ratio and by X-ray diffraction to determine the film structure. From the experimental values of lattice constant and UV–visible reflectance measurements, the position of silver atoms in Cu3N films was discussed. Finally, the effect of silver on the film electrical resistivity was presented.
... In Cu 3 N crystals, Cu atoms fail to occupy the position of (1 1 1) crystal surface, thereby leaving many gaps in the crystal structure. If other metal atoms enter into these gaps, then the electrical and optical properties will change significantly [10][11][12][13][14][15][16][17]. Some scholars calculated the crystal energy band structure of Cu 3 N by using the first principle, and they obtained an energy gap of approximately 1.0 eV [14,[18][19][20][21]. ...
... This finding is similar with previously reported preferred growth of the films under changes in doping contents or preparation conditions [6,[32][33][34][35]. Furthermore, the diffraction peak close to 56° is generated by the diffraction in the (2 2 0) crystal surface of Ag, which proved that Ag exist in the films as metal phase [17]. A strong diffraction peak, which is the small-angle (1 0 0) crystal surface, was used as reference. ...
... This finding is different from reports that lattice constant decreases after partial doping [6,9]. The lattice constant of Cu 3 N:Ag prepared under the same conditions in this study is relatively smaller than that of mostly reported values [1,17,37,38]. This difference may be caused by the different experimental preparation techniques. ...
Silver-doped copper nitride (Cu3N:Ag) films were prepared by using radio frequency and a direct current magnetron sputtering method. The effects of silver doping on the crystal structure, surface morphology, and optical properties of the films were investigated. Results demonstrated that Ag doping influences the preferred growth orientation of the films. With the increased Ag content, the films grow from the (1 0 0) crystal face to the (1 1 1) crystal face. Ag doping changes the lattice constant, grain size, and optical band gap of Cu3N:Ag films. Cu3N:Ag films achieve the most remarkable crystallinity at 0.23 at% of Ag with lattice constant and optical band gap of 0.381 88 nm and 1.30 eV, respectively. Moreover, the doped Ag atoms fill the hollows in the Cu3N lattice and consequently reach the high-energy defect level. These atoms also generate impurity compound centers at high-energy level, shorten the non-equilibrium carrier lifetime of the films, and weaken the electronic transportation of the films.
... Adapted with permission from Urban et al. 47 Deeper understandings on charge compensations, voltage decays and structural stabilities of LiTmO2 were obtained by researchers since 2016, following the O redox behavior has extensively attracted attentions. 49,50 While discussing charge compensations and atomic interactions, the Fermi level, which refers to a hypothetical energy level that has a 50% possibility of being occupied at thermodynamic equilibrium in the band structure of solids should be considered. In the cases of Li1+yTmzO2 materials with high oxidation-state redox species or large Li/Tm ratios, it is highly possible that the Fermi level will be located at states ...
... Linear coordinated ligands on Cu2O would increase the energy of the 1s → 4pz transition; thus, the 1s → 4pxy peak appears at a lower energy. [49][50][51] The gradual disappearance of the peak at 8985 eV proved that Cu + donated increasingly to the overall capacities upon charging. ...
... The specific cubic anti-ReO 3 structure gives a possibility of Cu 3 N modification by inserting other atoms into the inner and/or outer crystal lattice, which imposes significant changes in copper nitride physicochemical properties [2]. There are numerous computational studies confirming that the properties of Cu 3 N can be varied by doping various transition metal atoms, e.g., Sc, Ti, V, Cr, Mn, Cu, Zn, Pd, and Ag [3][4][5][6][7][8][9][10]. However, while different physical and chemical synthesis methods for binary Cu 3 N are known, the synthesis of ternary copper nitrides Cu 3 TM x N (TM = transition metal) is limited to physical vapor deposition (PVD), such as magnetron sputtering. ...
... One of the most intriguing TM dopants is silver since it is isovalent to copper, and thus, it could retain similar interactions after replacing the Cu atom [19]. According to reports, both the insertion of the silver atom in the interstitial sites and the replacement of the copper atom with silver expand the crystal unit cell [8,19]. This phenomenon can be related to the larger size of the silver atom (covalent radius 145 pm and Ag + ionic radius 129 pm) compared to the copper atom (covalent radius 132 pm and Cu + ionic radius 91 pm). ...
This work presents attempts to synthesize silver-doped copper nitride nanostructures using chemical solution methods. Copper(II) nitrate and silver(I) nitrate were used as precursors and the oleylamine as a reducing and capping agent. Homogeneous Cu 3 N/Ag nanostructures with a diameter of ~ 20 nm were obtained in a one-pot synthesis by the addition of the copper(II) salt precursor to the already-synthesized silver nanoparticles (Ag NPs). Synthesis in a two-pot procedure performed by adding Ag NPs to the reaction medium of the Cu 3 N synthesis resulted in the formation of a Cu 3 N@Ag nanocomposite, in which Ag NPs are uniformly distributed in the Cu 3 N matrix. The morphology, structure, and chemical composition of the obtained specimens were studied by TEM, XRD, XPS, and FT-IR methods, while optical properties using UV–Vis spectroscopy and spectrofluorimetry. The band gap energy decreased for Cu 3 N/Ag ( E g = 2.1 eV), in relation to pure Cu 3 N ( E g = 2.4. eV), suggesting the insertion of Ag atoms into the Cu 3 N crystal lattice. Additionally, Cu 3 N and Cu 3 N/Ag nanostructures were loaded on graphene (GNP) and tested as a catalyst in the oxygen reduction reaction (ORR) by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The Cu 3 N/Ag-modified GNP hybrid material revealed catalytic activity superior to that of Cu 3 N-based GNP hybrid material and pure GNP, comparable to that of a commercial Pt/C electrode.
Graphical Abstract
... Cui et al have studied the magnetic properties of the 3d transition metal doped Cu 3 N by first principles [10]. And on the experimental side, there are also some reports of Cu 3 N films doped with a transition metal element [11][12][13][14][15][16][17][18][19]. Metallic Cu 4 N in which the extra Cu atom resides in the centre of the unit cell was reported first [11]. ...
... The insertion of Zn into the body-centre sites of Cu 3 N results in the decreasing of electrical resistivity [16]. The introduction of Ag induced copper vacancies and decreased the electrical resistivity [17]. In order to adjust and explore its properties, more studies still need to be done on the doping of Cu 3 N films with different foreign elements. ...
Fe-doped Cu3N films were prepared by cylindrical magnetron sputtering equipment at room temperature. The doping of Fe with the proper concentration results in a change in the preferred growth orientation from the Cu-rich plane (1 1 1) to the N-rich plane (1 0 0), which relates to the evolution of the surface grain shape from pyramid to sphere. Excessive doping of Fe is not favourable for the crystallization of Cu3N films. The cross-sections of the doped films with preferred growth orientations of [1 0 0] exhibit regular columnar grains. The variation between the lattice constant and the XPS results reveals that Fe probably replaces the position of Cu atoms in the lattice or is segregated in the grain boundaries. Weaker bonding of Cu–N results in a reduction of thermal stability for Fe-doped Cu3N films. And the incorporation of Fe can effectively modify the energy gap. According to the variations in the mean grain size, the peak of N1s and the energy gap, it is inferred that a doping limitation exists around 2.0 at%.
... This should result from some possible vacant positions of Ti in the hcp structure, probably because Ti atoms are establishing intermetallic bonds with the few Ag atoms that arrived on the growing film since the standard enthalpies of formation of Ag-Ti compounds are favorable [33]. Furthermore, and since Ag and Ti atoms exhibit similar atomic radii [34], the substitution of Ti by Ag should not be disregarded [35]. At the same time, there is no clear evidence for the presence of a silver phase for this low Ag content zone. ...
... In addition, the low adatom mobility due to relatively low deposition temperature (100 • C), associated with the absence of ion bombardment (films were grown in ground condition) would certainly favor these Ag incorporations in the Ti lattice. This incorporation would lead to cumulative local lattice disorder, and thus to a progressive tendency to the amorphization of the Ti phase [35]. ...
... The evolution of the film lattice constant is due to the variation in nitrogen stoichiometry [24][25][26]. However, there is no information about the position of excess nitrogen in the Cu 3 N unit cell [24]. ...
... The evolution of the film lattice constant is due to the variation in nitrogen stoichiometry [24][25][26]. However, there is no information about the position of excess nitrogen in the Cu 3 N unit cell [24]. Due to sensitivity of (Figure 1). ...
A metalloid Ti13Cu87 target was sputtered by reactive DC magnetron sputtering at various substrate temperatures in an Ar- N2 mixture ambient. The sputtered species were condensed on Si (111), glass slide and Potsssium bromide (KBr) substrates. The as-deposited films were characterized by X ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscope (SEM), energy dispersive X ray spectroscopy (EDX), optical spectrophotometry and four point probe technique.
The as-deposited films present composite structure of nano- crystallite cubic anti-ReO3 structure of Ti inserted Cu3N (Ti:Cu3N) and nano- crystallite face centre cubic (fcc) structure of Cu. The titanium atoms and sequential nitrogen excess form a solid solution within the Cu3N crystal structure and accommodate in crystal lattice and vacant interstitial site, respectively. Depending on substrate temperature, unreacted N atoms inter-diffuse between crystallites and their (and grain) boundaries. The films have agglomerated structure with atomic Ti:Cu ratio less than that of the original targets. A theoretical model has been developed, based on sputtering yield, to predict the atomic Ti:Cu ratio for the as-deposited films. Film thickness, refractive index and extinction coefficient are extracted from the measured transmittance spectra. The films’ resistivity is strongly depending on its microstructural features and substrate temperature.
... The evolution of the film lattice constant is due to the variation in nitrogen stoichiometry [24][25][26]. However, there is no information about the position of excess nitrogen in the Cu 3 N unit cell [24]. ...
... The evolution of the film lattice constant is due to the variation in nitrogen stoichiometry [24][25][26]. However, there is no information about the position of excess nitrogen in the Cu 3 N unit cell [24]. Due to sensitivity of (Figure 1). ...
A metalloid Ti 13 Cu 87 target was sputtered by reactive DC magnetron sputtering at various substrate temperatures in an Ar-N 2 mixture ambient. The sputtered species were condensed on Si (111), glass slide and Potsssium bromide (KBr) substrates. The as-deposited films were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), optical spectropho-tometry and four point probe technique. The as-deposited films present composite structure of nano-crystallite cubic anti-ReO 3 structure of Ti inserted Cu 3 N (Ti:Cu 3 N) and nano-crystallite face centre cubic (fcc) structure of Cu. The titanium atoms and sequential nitrogen excess form a solid solution within the Cu 3 N crystal structure and accommodate in crystal lattice and vacant interstitial site, respectively. Depending on substrate temperature, unreacted N atoms inter-diffuse between crystallites and their (and grain) boundaries. The films have agglomerated structure with atomic Ti:Cu ratio less than that of the original targets. A theoretical model has been developed, based on sputtering yield, to predict the atomic Ti:Cu ratio for the as-deposited films. Film thickness, refractive index and extinction coefficient are extracted from the measured transmittance spectra. The films' resistivity is strongly depending on its microstructural features and substrate temperature.
... Este tipo de estructura cristalina, abierta y de baja densidad, es ideal para la inserción de átomos metálicos en los sitios intersticiales, específicamente en la posición del centro del cuerpo (½, ½, ½). La inserción de elementos metálicos adicionales altera las interacciones químicas entre los átomos de cobre y nitrógeno, lo que afecta de manera importante la estructura electrónica del material (Maruyama et al., 1995), (Fan et al., 2007), (Pierson et al., 2008). En particular, estudios experimentales y computacionales han demostrado que el Cu3N adquiere propiedades metálicas como resultado del dopaje (Moreno-Armenta et al., 2007), (Li et al., 2009), (Zhao et al., 2016). ...
El nitruro de cobre (Cu3N) es un material prometedor en aplicaciones como la microelectrónica y energías renovables, donde su optimización depende de entender cómo las condiciones de depósito afectan sus propiedades. En este estudio se utilizó la técnica de erosión catódica reactiva para depositar películas delgadas de Cu3N a temperaturas desde ambiente hasta 300 °C y se analizaron sus propiedades estructurales, ópticas y eléctricas mediante las técnicas de XRD, espectrofotometría VIS-NIR y efecto Hall, respectivamente. Se observó que la resistividad disminuye y la movilidad de portadores aumenta con la temperatura, alcanzando valores característicos de los metales a 300 °C. A esta temperatura, se evidencia una descomposición parcial del Cu3N en cobre metálico, lo que se refleja en una baja transmitancia y picos que identifican al Cu en difracción de rayos x. Estos resultados sugieren que ajustar la temperatura de depósito puede modificar las propiedades optoelectrónicas de las películas de Cu3N, lo que es relevante para el desarrollo de dispositivos semiconductores.
... Thin films' optical characteristics were the interest of many researchers, both thermal stability and electrical conductivity of Cu3N thin films gave huge interest and became the center of attention in semiconductor materials due the special composition & physical chemical properties (1-2). By adding other different atoms in (Cu3N) crystals, the Cu3N thin films' composition may be changed, thus allowing the Cu3N conversion to be semiconductors or even conductors from dielectrics [3][4]. Cu3N offers promise probability and benefits for uncomplicated elaboration and toxicity. ...
The plasma diagnostics of dc magnetron reactive sputtered copper nitride thin films by Optical emission spectrometer (OES) is investigated and argon / nitrogen effect (Ar/N 2 ) mixture ratio on plasma parameters and structural properties of sputtered Cu 3 N thin films are discussed. Cu 3 N thin films of 60.30 nm and 105 nm have been formed on glass substrates at room temperature using Ar(70)/N 2 (30) and Ar(50)/N 2 (50) working gas discharges respectively. The size of crystallites, grains and particles in the copper nitride thin films have been estimated from X-ray diffractions, Atomic Force Microscope (AFM), and Field Emission Scanning microscope (FESEM) respectively. The properties of sputtered copper nitride thin films are related to the plasma parameter of electrons temperature and density.. An increase in optical transmittance and a decrease in absorbance over the wavelength range were found as the nitrogen percentage increased which result on decrease the film thicknesses. The energy of the optical band gap, E g obtained in the range of 2.6 to 2.7 eV.
... many types of semiconductors to enhance light absorption from the ultraviolet to visible light regions [7,24], increase the separation and lifetime of charge carriers, and provide potential applications in visible-light catalysis [25,26]. Cu 3 N is a widely used material because of its metal-to-semiconductor properties [27,28]. Cu 3 N has been proposed for battery materials [2,29], catalyst additives [30], spin tunnel junction [31], memory [32], and electric transport materials [33] due to its wide range of optical band gap, low temperature of thermal decomposition, and excellent chemical activity. ...
Cu3N/MoS2 heterojunction was prepared through magnetron sputtering, and its optical band gap was investigated. Results showed that the prepared Cu3N/MoS2 heterojunction had a clear surface heterojunction structure, uniform surface grains, and no evident cracks. The optical band gap (1.98 eV) of Cu3N/MoS2 heterojunction was obtained by analyzing the ultraviolet-visible transmission spectrum. The valence and conduction band offsets of Cu3N/MoS2 heterojunction were 1.42 and 0.82 eV, respectively. The Cu3N film and multilayer MoS2 formed a type-II heterojunction. After the two materials adhered to form the heterojunction, the interface electrons flowed from MoS2 to Cu3N because the latter had higher Fermi level than the former. This behavior caused the formation of additional electrons in the Cu3N and MoS2 layers and the change in optical band gap, which was conducive to the charge separation of electrons in MoS2 or MoS2 holes. The prepared Cu3N/MoS2 heterojunction has potential application in various high-performance photoelectric devices, such as photocatalysts and photodetectors.
... Although the Cu3N film alone has better photocatalytic performance, it still has some shortcomings, so researchers often dope or recombine Cu3N with other materials. Cu3N has a ReO3 structure, and the eight corners of the cubic crystal are occupied by N atoms; each side of the unit cell has a Cu atom, and many vacancies are present in the center of the unit cell [36][37][38][39]. These vacancies can be filled by other atoms (e.g., Pb [40], Ag [33], and Sc [41]), thereby changing the Cu3N band gap width and consequently its electrical and optical properties. ...
Cu3N/MoS2 composite films were prepared by magnetron sputtering under different preparation parameter, and their photocatalytic properties were investigated. Results showed that the composite films surface was uniform and had no evident cracks. When the sputtering power of MoS2 increased from 2 W to 8 W, the photocatalytic performance of the composite films showed a trend of increasing first and then decreasing. Among these films, the composite films with MoS2 sputtering power of 4 W showed the best photocatalytic degradation performance. The photocatalytic degradation rate of methyl orange at 30 min was 98.3%, because the MoS2 crystal in the films preferentially grew over the Cu3N crystal, thereby affecting the growth of the Cu3N crystal. The crystallinity of the copper nitride also increased. During photocatalytic degradation, the proper amount of MoS2 reduced the band gap of Cu3N, and the photogenerated electron hole pairs were easily separated. Thus, the films produces additional photogenerated electrons and promotes the degradation reaction of the composite films on methyl orange solution.
... Weak doping of Ti can promote the nitridation of Cu in the film and raise the decomposed temperature by 50 C [24] . The introduction of Ag induces copper vacancies and decreases the electrical resistivity [25] . The doping of Fe can reduce the thermal stability. ...
Mn-doped Cu 3 N films were deposited by cylindrical magnetron sputtering equipment on the common glass at room temperature. The incorporation of Mn can change the preferred growth orientation from Cu-rich plane (111) to N-rich plane (100) due to the improvement of nitridation of Cu. The shrinkage of the lattice and the X-ray photoelectron spectroscopy results reveal that Mn should replace Cu atoms in the lattice or be segregated in the grain boundaries. The thickness of Mn-doped film is smaller than that of the pure one due to the less physisorption of N species among the columnar grains. The mean grain size and the energy gap become larger with increasing Mn concentration to 2.2 at.% and then decrease when the concentration of Mn is higher than 2.2 at.%. Notably, weak doping of 1.5 at.% Mn successfully promotes the decomposed temperature by ~50 C. According to the results of XRD and SEM for Mn-doped films annealed in vacuum, a possible decomposed mechanism with increasing the annealing temperature is proposed.
... From Fig.4, it is clearly observed that the resistivity changes from 2.21 Ω.cm (semiconductor) to be close to a conductor at 4.6x10 -3 Ω.cm. In conclusion, the effect of metallic nickel is similar to the doping of Ag [7], Al [8], and Zn [9] and contrary to the work of Fan et al. [10]. Moreno-Armenta et al. [11] have used Ab initio total energy calculations, showing that copper nitride is an indirect semiconducting material with a band gap close to 0.25eV. ...
Ni-doped copper nitride films have been prepared by co-sputtering of Ni and Cu targets. The addition of Ni to Cu3N films reduced the intensity of the (111) diffraction peak, and lead a little angular shifts of the peaks. The films showed a large difference in reflectance in the infrared and visible before and after thermal decomposition, which is applicable to optical recording media. The films change from a semiconductor to a conductor with the increased ratio of Ni in Cu3N films.
... Up to now the doping possibilities have been utilised by several researchers for doping of Cu 3 N with a metal in order to influence for example the electrical and optical properties of the material. For instance doping with metals such as Pd [45], Cu, Li [46], Al [47], Ti [48][49] and Ag [50] but also with non-metals such as H [51][52][53][54] and O [55][56] have been reported. ...
... Silver copper nitride is unknown until now, and only copper nitride films deposited with Ag by reactive magnetron sputtering have been reported recently [68]. ...
In my thesis preparative and structural studies of silver nitrides are discussed. Ag3+xN is found to adopt a perovskite structure with partially filled A site. For the preparation of such silver nitrides an ammonolysis reaction has been used, and this method has been applied for the synthesis of other noble metal nitrides, such as Pd, Au and Hg nitrides. Attempts for the preparation of ternary nitrides, e.g. silver copper nitride, have also been done, which requires AgCuF3 as a precursor.
AgCuF3 and its isostructural analogue NaCuF3 crystallize in a distorted variant of the GdFeO3 type structure with symmetry. They exhibit interesting magnetic properties, and become typical 1D antiferromagnets at low temperature, correlated to cooperative Jahn-Teller effect. Cs2AgF4 crystallizes in the K2NiF4-type structure, and its magnetic and optical properties have been studied. It behaves as a 2D square-lattice Heisenberg ferromagnet, which is associated with orbital order.
CsF has a strong tendency to form fluoride complexes, and includes easily molecules like H2O or Br2. We have studied the possibilities of the inclusion of tetrahedral molecules, e.g. OsO4 and P4, into the CsF lattice. From the reaction of CsF with OsO4 an oxyfluoride, Cs3OsO4F3, is formed, which contains [OsO4F2] octahedral units and [Cs2F] layers. In contrast, P4 is not included into the CsF lattice, but transformed into black amorphous phosphorus.
In the last part of my thesis, structural studies have been performed on SiBr4 (m.p. 278 K), the only tetrahedral EX4 compound (E = C, Si, Ge, Sn, Pb; X = F, Cl, Br, I) for which no structural data has yet been reported. A full crystal-structure prediction of SiBr4 by lattice-energy minimizations was done in collaboration with A. Wolf from University Frankfurt am Main. The structures of two polymorphs of SiBr4, a high temperature phase (Pa-3) and a low temperature phase (P21/c) have been experimentally determined from the refinements of X-ray and synchrotron powder diffraction data as well as single crystal diffraction data. The transition temperature and halogen-halogen interactions of the experimental and calculated structures are discussed.
... It contains a rather large void at the center of the cubic unit cell, as shown in Fig. 1. This void can host extrinsic atoms such as N [18], Li [19,20], Pd [21][22][23][24][25], Rh, Ru [25], Zn, Ni, Cd [21], Cu [20,26], Fe, Ti [27], Ag [28], La, Ce [29], as well as many other transition-metal atoms [30]. In particular Ni, Cu, Pd, An, Ag, and Cd [21] are found to drive an electronic transition in Cu 3 N into a semimetal without breaking T symmetry [30], by which we expect that DLNs form near the Fermi energy. ...
We propose and characterize a new class of topological
semimetals with a vanishing spin--orbit interaction. The proposed topological
semimetals are characterized by the presence of bulk one-dimensional (1D) Dirac
Line Nodes (DLNs) and two-dimensional (2D) nearly-flat surface states,
protected by inversion and time--reversal symmetries. We develop the
invariants dictating the presence of DLNs based on parity
eigenvalues at the parity--invariant points in reciprocal space. Moreover,
using first-principles calculations, we predict DLNs to occur in CuN near
the Fermi energy by doping non-magnetic transition metal atoms, such as Zn and
Pd, with the 2D surface states emerging in the projected interior of the DLNs.
This paper includes a brief discussion of the effects of spin--orbit
interactions and symmetry-breaking as well as comments on experimental
implications.
... This explanation is also in good agreement with the SEM measurements. Addition, the effect of metallic manganese is similar to that in the work of Fan et al. [3], and contrary to the doping of Ag [13], Al [14], and Zn [15]. X.Y. ...
Mn-doped Cu3N films were prepared by radio frequency reactive magnetron sputtering method under different manganese concentration. The deposits exhibit a satisfactory crystallinity and a preferred growth orientation along the (111) plane. The shapes of crystalline grains vary from pyramid-like to rugby-ball-like with the Mn-doping constituent in Cu3N film reaching 0.02%. The electrical resistivity of Mn-doped Cu3N films has dramatically increased from 0.102×10³ Ω·cm to 0.495×10³ Ω·cm at room temperature. Moreover, the reflectivity difference and ferromagnetic property have also been investigated.
... It exhibits a large vacant site at the centre of the cell, which can be used for doping and varying the properties. Hence other metallic atoms (such as Pb, Pd, Ag, Zn) can be inserted into the body center of the cubic unit cell to induce changes in remarkable change of the electrical and optical properties [1][2][3][4]. Cu 3 N is a metastable material and is easy to decompose under heating or by ion, electron or laser beam irradiation, which can be used for patterning of structures [5][6][7]. In addition, Optical reflectivity of Cu 3 N in the visible and infrared range is far smaller than that of pure Cu [6,8]. ...
In this paper, influence of nitrogen content on growth mode, surface morphology and the optical properties of copper nitride (CuxN) films was investigated. CuxN films were prepared on glass substrates by direct current (DC) magnetron sputtering at various nitrogen contents. X-ray diffraction (XRD), profilometer, atomic force microscope (AFM) and spectrophotometer were used to analyze the characteristics. The XRD measurements showed the films were composed of Cu and Cu4N crystallites at working pressure with a low nitrogen content, while the structure of the films were conformed to anti-ReO3 structure at a high nitrogen content and the preferred growth orientations of the Cu3N films changed from (111) to (100). The transmittances of CuxN films increased with the increase of nitrogen content (r) in working gas flow from 0 to 0.6, while decreased when r increased from 0.6 to 0.9. Additionally, the lowest reflectivity and the maximum band gap of 1.35 eV for CuxN film were obtained at r = 0.6. The CuxN films deposited at various nitrogen contents have large differences on optical properties which provide a potential application in optical storage devices.
... According to the theoretical works, Cu 3 N is a semiconductor with a narrow band gap in the range of 0.23-0.9 eV [6, 10, 21-25] while, experimental results vary between 0.8 and 1.9 eV [7,[26][27][28][29][30]. It should be pointed out that experimental estimation of band gap is performed by Table 2. Calculated mass density ρ(g cm −3 ), sound velocities (m s −1 ), for longitudinal and shear waves (V l and V s ), Debye average velocity V m (m s −1 ) and Debye temperature D (K) of Cu 3 N. optical absorption. ...
The structural, optical and electronic properties of the copper nitride (Cu3N) bulk structure under pressure have been studied by performing accurate total energy calculations in the framework of density functional theory using the full-potential linearized augmented plane wave method. Perdew-Burke-Ernzerhof and modified Becke-Johnson parameterizations of the generalized gradient approximation were employed to obtain the structural and electronic properties of Cu3N. The most stable crystal structure of the Cu3N compound was found to be cubic anti-ReO3 at ambient pressure. Moreover, the calculation of the enthalpy of different crystal structures of Cu3N for different pressures indicates that the anti-ReO3 cubic phase undergoes a structural phase transition for pressures higher than 30 GPa. The study of the elastic constants of the anti-ReO3 cubic phase confirms that Cu3N is mechanically stable under hydrostatic pressures up to 30 GPa. Moreover, with the application of pressure, the C44 elastic constant, shear module and Debye temperature deviate from linear behavior at 10 GPa. An electronic study shows that there is an electronic-type phase transition from semiconductor to metal between 5 and 10 GPa and metal to semi-metal between 20 and 30 GPa applied pressures. Cu3N is an indirect band gap semiconductor with a value of 0.56 eV.
... The incorporation of a foreign metal can significantly modify the energy band structure, bringing a remarkably change in the thermal stability, the optical and electrical properties of this material. Various metals, such as lithium, palladium, and sil-ver, have been applied to obtain Cu 3 NM x thin films, [18][19][20][21][22][23][24][25] in which some interesting new properties have been measured. Remarkably, in the Cu 3 NPd 0.238 sample a constant electrical resisitivity over a temperature range of more than 200 • C has been achieved. ...
Thin films of ternary compounds CuxInyN and CuxTiyN were grown by magnetron sputtering to improve the thermal stability of Cu3N, a material that decomposes below 300 °C, and thus promises many interesting applications in direct-writing. The effect of In or Ti incorporation in altering the structure and physical properties of copper nitride was evaluated by characterizing the film structure, surface morphology, and temperature dependence of electrical resistivity. More Ti than In can be accommodated by copper nitride without completely deteriorating the Cu3N lattice. A small amount of In or Ti can improve the crystallinity, and consequently the surface morphology. While the decomposition temperature is rarely influenced by In, the Ti-doped sample, Cu59.31Ti2.64N38.05, shows an X-ray diffraction pattern dominated by characteristic Cu3N peaks, even after annealing at 500 °C. Both In and Ti reduce the bandgap of the original Cu3N phase, resulting in a smaller electrical resistivity at room temperature. The samples with more Ti content manifest metal-semiconductor transition when cooled from room temperature down to 50 K. These results can be useful in improving the applicability of copper—nitride-based thin films.
... So far, the research about the interstitially doped Cu 3 N is dominated by theoretical investigations. First-principles calculation of the structural and electronic properties of Cu 3 NM compounds (with M 5 Ni, Cu, Zn, Pd, Ag and Cd) and some experiment results reveal that the incorporation of foreign metal atoms in the cell centers of the cubic lattice modifies the electronic structure of Cu 3 N and all such Cu 3 NM compounds are metallic [13][14][15]16 . Notably, report on the synthesis of the samples of well determined composition and atomic structure, and property measurement and mechanism (particularly for electrical transport) discussion based on experimental data are comparatively rare 17,18 . ...
Electrical resistance is a material property that usually varies enormously with temperature. Constant electrical resistivity over large temperature range has been rarely measured in a single solid. Here we report the growth of Cu3NMx (M = Cu, Ag, Au) compound films by magnetron sputtering, aiming at obtaining single solids of nearly constant electrical resistance in some temperature ranges. The increasing interstitial doping of cubic Cu3N lattice by extra metal atoms induces the semiconductor-to-metal transition in all the three systems. Nearly constant electrical resistance over 200 K, from room temperature downward, was measured in some semimetallic Cu3NMx samples, resulting from opposite temperature dependence of carrier density and carrier mobility, as revealed by Hall measurement. Cu3NAgx samples have the best performance with regard to the range of both temperature and doping level wherein a nearly constant electrical resistance can be realized. This work can inspire the search of other materials of such a quality.
... Copper nitride is a metastable semiconducting material with a cubic anti-ReO 3-type crystal structure where the face-centered-cubic close-packed sites are vacant [22]. Thus, copper nitride has potential for the incorporation of other elements such as Pd, Ag and the formation of ternary compounds [23][24][25]. ...
Ternary (Ti,Cu)N thin films were deposited by reactive dc magnetron sputtering on Si (111), glass slide, quartz and potassium bromide (KBr) substrates in molecular nitrogen ambient. This work has provided insight into the effects of substrate temperature, nitrogen content and particle and energy flux toward the substrate on the characteristics of (Ti,Cu)N films. Structural analysis of the films was identified by the x-ray diffraction (XRD) technique. Crystalline quality and phase stability are strongly dependent on substrate temperature. Ti-accommodated Cu3N structure results in lattice constant expansion and (100) preferential orientation. The bonding environment in these films was obtained by Fourier transform infrared (FTIR) spectroscopy. The surface morphology and chemical composition of the films were studied by using a scanning electron microscope (SEM)/energy dispersive x-ray spectroscopy (EDX). The films were aggregated as spherical grains. The atomic titanium to copper (Ti : Cu) ratio of (Ti,Cu)N films was less than that of the original target. An optical study was performed by vis–near-IR transmittance spectroscopy. The film thickness, refractive index and extinction coefficient were extracted from the measured transmittance. The as-deposited (Ti,Cu)N films are direct semiconductors with bandgap energy in the range of 2.57–3.23 eV. Nitrogen richness acts as an acceptor center and injects holes into the valence band (excited semiconductor). The amount of N attracted by the films was calculated using a model based on chemical bonding and the solubility process. Energy and angular contributions of sputtering yield were extracted from the existing literature to obtain a prediction about the atomic Ti : Cu ratio. By means of transport and range of ions in matter (TRIM.SP) Monte-Carlo simulation, the particle reflection coefficient of reflected N-neutrals was calculated. The initial energy of reflected N-neutrals and the sputtered particle at the substrate were estimated using a simple binary collision model and distribution weighted average, respectively. Their final energy was evaluated by energy dissipation considerations during mass transport through the gas phase. The total energy flux at the substrate during sputter deposition was estimated in order to assess the surface temperature during film growth.
All-solid-state fluoride-ion batteries (FIBs) have attracted extensive attention as candidates for next-generation energy storage devices; however, promising cathodes with high energy density are still lacking. In this study, Cu3N is investigated as a cathode material for all-solid-state fluoride-ion batteries, which offers enough anionic vacancies around the 2-fold coordinated Cu center for F⁻ intercalation, thereby enabling a multielectron-transferred fluorination process. The contribution of both cationic and anionic redox to charge compensation, in particular, the generation of molecular nitrogen species in highly charged states, has been proved by several synchrotron-radiation-based spectroscopic technologies. As a result, Cu3N exhibits a high reversible capacity of ~550 mAh g⁻¹, exceeding many conventional fluoride-ion cathodes. It is believed that the new charge compensation chemistry as well as the unique intercalation behaviors of novel mixed-anion Cu-N/F local structures could bring new insights into energy storage materials.
Promising optoelectronic properties of semiconducting copper nitride (Cu3N), have brought the material into limelight for numerous device applications. As band gap (Eg), undoubtedly is a key parameter in determining proficiency of a semiconductor in optoelectronics, hence its modulation needs clear understanding both from the fundamental and application perspectives. The present study discusses the impact of inherent onsite Coulomb-correlation (through Hubbard U) and strain on the electronic properties of pure and iso-electronic element (Ag) doped Cu3N using density functional calculations. A slow rate of increase in Eg with U recognizes Cu3N a weakly correlated system. Alternately, U for the doped system (Cu2AgN) is discovered to have further weaker effect on the Eg, nearly independent for U > 2 eV. However, doping of the 4d electronic element in the 3d transition metal nitride predicts an increased carrier mobility which will subsequently improve electrical conductivity. While examining the effect of strain in pristine Cu3N, the lowest conduction band is found to have both approaching and avoiding feature with respect to the Fermi level at two different high symmetry k-points. Consequently, Eg decreases (increases) for the compressive (tensile) strain which is attributed to the higher (lower) dispersive nature of the valence bands due to stronger (weaker) p-d hybridization. In case of Cu2AgN, though a similar shifting in the lower conduction band is observed, the variation of Eg with strain is quite different to that of Cu3N. While Eg increases (decreases) for the uniaxial compressive (tensile) strain, it decreases both for tensile and compressive strains corresponding to the isotropic deformations.
In the present work, structural, elastic and mechanical properties of pure and Ag doped Cu3N systems are investigated using density functional calculations. The doped atom is incorporated into the host lattice by filling the vacant interstitial site (interstitial doping) or substituting Cu (substitutional doping). From the calculated elastic constants, the pure and both kinds of doped systems are qualified as mechanically stable compounds. Modifications of the elastic and mechanical properties of Cu3N due to the interstitial and substitutional Ag doping are systematically predicted by analyzing the estimated elastic moduli (Young’s, bulk and shear moduli, and Poisson’s ratio), Pugh’s constant and Vicker’s hardness. The results predict, interstitial (substitutional) doping of Ag strengthens (weakens) mechanical stability of the parent compound. Further, elastic anisotropy of these systems is examined by estimating various anisotropy factors and mapping spatial variation of the elastic moduli. The anisotropy of elastic properties of Cu3N is greatly reduced when Ag is doped at the interstitial site. On the other hand, substitutional Ag doping magnifies the elastic anisotropy. Finally, velocity of acoustic waves is estimated from the elastic constants and its anisotropy is examined. It is verified that, both kinds of Ag doping reduce the average acoustic velocity.
Herein we describe an alternative strategy to achieve the preparation of nanoscale Cu3N. Copper(II) oxide/hydroxide nanopowder precursors were successfully fabricated by solution methods. Ammonolysis of the oxidic precursors can be achieved essentially pseudomorphically to produce either unsupported or supported nanoparticles of the nitride. Hence, Cu3N particles with diverse morphologies were synthesized from oxygen-containing precursors in two-step processes combining solvothermal and solid−gas ammonolysis stages. The single-phase hydroxochloride precursor, Cu2(OH)3Cl was prepared by solution-state synthesis from CuCl2·2H2O and urea, crystallising with the atacamite structure. Alternative precursors, CuO and Cu(OH)2, were obtained after subsequent treatment of Cu2(OH)3Cl with NaOH solution. Cu3N, in the form of micro- and nanorods, was the sole product formed from ammonolysis using either CuO or Cu(OH)2. Conversely, the ammonolysis of dicopper trihydroxide chloride resulted in two-phase mixtures of Cu3N and the monoamine, Cu(NH3)Cl under similar experimental conditions. Importantly, this pathway is applicable to afford composite materials by incorporating substrates or matrices that are resistant to ammoniation at relatively low temperatures (ca. 300 °C). We present preliminary evidence that Cu3N/SiO2 nanocomposites (up to ca. 5 wt.% Cu3N supported on SiO2) could be prepared from CuCl2·2H2O and urea starting materials following similar reaction steps. Evidence suggests that in this case Cu3N nanoparticles are confined within the porous SiO2 matrix.
The effects of Ag doping on structural, thermodynamical and electronic properties of Cu3N are investigated using density functional calculations. The doped atom is introduced into the host lattice in two possible ways: filling the vacant interstitial site (interstitial doping) and substituting Cu (substitutional doping). Though volume of the lattice expands in both the cases, the variation of lattice parameters is strictly dependent on impurity sites in case of substitutional doping whereas for interstitial doping, no such dependency is noticed. Similar to their parent compound, both the doped systems are thermodynamically metastable. A thorough investigation of the electronic structure successfully demonstrates host-impurity covalent bonding mechanism and formation of energy bands out of these interactions. The results predict an indirect band gap semiconducting nature for the substitutional doped system, however with a reduced energy gap compared to the pure compound. On the other hand, interstitial Ag doping in Cu3N induces semimetallic behavior.
Cu3N with a cubic crystal structure has been prepared from Cu on fused SiO2 under a flow of NH3 : O2 between 400°C and 600°C. All Cu3N layers exhibited distinct maxima in differential transmission at ∼ 500 nm, 550 nm, and 630 nm, 670 nm with the same spectral structure and shape on an ps time scale as shown by ultrafast pump-probe spectroscopy. We show that the maxima at 630 nm (≡ 1.97 eV) and 670 nm (≡ 1.85 eV) correspond to the M and R direct energy band gaps of Cu3N in excellent agreement with density functional theory calculations of the electronic band structure. These findings are corroborated further by the fact that Cu3N as-deposited by reactive sputtering under 100% N2 at 25°C and 10-2 mbar did not exhibit a fine spectral structure, due to a smeared density of states, poor crystallinity and a high density of defects but annealing under NH3 : H2 at 300°C revealed a similar spectral structure compared to Cu3N obtained from Cu under NH3 : O2</sub. In contrast to the above we suggest that the peaks at 500 nm (≡2.48 eV) and 550 nm (≡2.25 eV) might correspond to the M and R direct gap of certain regions of Cu<sub>3N under strain that changes the lattice constant and band gap. We discuss the charge carrier generation and recombination mechanisms in terms of Cu interstitials and vacancies that are known to be energetically located near the band edges thus allowing the observation of the direct energy band gaps in this defect tolerant semiconductor.
Cu3NPdx thin films have been successfully prepared on glass substrates by a facile chemical solution deposition. Phase composition and surface morphology are evaluated by X-ray diffraction and field-emission scanning electronic microscope. The X-ray diffraction and X-ray photoelectron spectroscopy results reveal that palladium will occupy the body centre position. Pd dependent electrical and optical properties of the Cu3NPdx thin films are investigated. Electrical conductivity can be greatly improved and the indirect bandgap is decreased with increasing the palladium doping, and the optical band gap can be adjusted within the range of 1.40–1.04 eV. The results will provide a facile solution route to synthesize high-quality copper nitride thin films with low-cost and controllable optoelectronic performance.
Copper nitride (Cu3N) thin films display typical trans-rhenium trioxide structures. They exhibit excellent physical properties, low cost, nontoxicity, and high stability under room temperature. However, they possess low-thermal decomposition temperature, and their lattice constant often changes significantly with prepared technologies or techniques, thereby enabling the transformation from insulators to semiconductors and even conductors. Moreover, Cu3N thin films are becoming the new research hotspot of optical information storage devices, microelectronic semiconductor materials, and new energy materials. In this study, existing major prepared technologies of Cu3N thin films are summarized. Influences of prepared technologies of Cu3N thin films on crystal structure of films, as well as influences of prepared conditions and methods (e.g., nitrogen pressure, deposition power, substrate temperature, and element addition) on crystal structure and optical, electrical, and thermal properties of films were analyzed. The relationship between crystal structure and physical properties of Cu3N thin films was explored. Finally, applications of Cu3N thin films in photoelectricity, energy sources, nanometer devices, and other fields were discussed.
Copper nitride, Cu3N, is a metastable material whose properties can be changed considerably by doping with metals which opens for a variety of applications in several areas (sensors, electrical connects, batteries, memories, etc.). The present work is a systematic study in the system Cu-Ni-N of preferences regarding occupation of interstitial and substitutional crystallographic sites in the Cu3N structure as the metal dopant level increases and how the occupation influences growth behavior, texture, microstructure and resistivity. Ni doped Cu3N films of different chemical composition were grown by a gas-pulsed Chemical Vapor Deposition technique. The occupation of the different crystallographic sites of the Cu3N by the Ni atoms was obtained from analysis of X-ray diffraction data. At low Ni content, less than about 21% in metal content, Ni replaced the Cu atoms in the structure. In the intermediate Ni metal content range from about 21 to 40% the vacant centre position became available. After filling the centre position, substitution of Cu for Ni occurred up to a Ni content of about 80% (Cu0.8Ni3.2N) which is the solid solubility limit of Ni in Cu3N. The film resistivity decreased rapidly by adding nickel to the Cu3N structure from about 10⁹ μΩ·cm without any Ni doping to about 100 μΩ·cm with 80% Ni in the metal content. After filling the centre position the change in resistivity when Cu atoms were substituted for Ni was very small. Finally, the growth mechanism, texture and microstructure changed significantly with the uptake of Ni atoms in the structure.
Co-doped copper nitride films were successfully prepared on various substrates by reactive magnetron co-sputtering. We study the surface chemicals, structures, electrical resistivity, optical transmittance and magnetic properties of Co-doped Cu3N films. X-ray diffraction patterns show that the Co-doped films more readily exhibit diffraction peaks on different orientations when deposited on ITO glass substrates. The resistivity of the films significantly decreases from 5730 Ω·cm to 225 Ω·cm with increasing content of Co. Vibrating sample magnetometer tests show that magnetic films were obtained via Co doping.
The electrode materials with low diffusion energy barriers and high storage capacity of lithium are crucial for high performance rechargeable lithium-ion batteries (LIBs). Based on first-principles calculations, we demonstrate a new class of electrode materials. Taking advantage of the large voids in Cu3N crystal, high lithium mobility and storage capacity can be achieved. The diffusion of Li on Cu3N nanosheets experiences an energy barrier of about 0.09 eV, much lower than those of the presently-proposed electrode materials. The maximum Li capacity of Cu3N nanosheets can reach 1008 mA hg-1. In view of a large number of crystals sharing the same lattice structure as Cu3N, this work opens an avenue for developing electrode materials of high performance LIBs.
The simple fluorinated precursor, copper(ii) trifluoroacetate, Cu(CF3COO)2 can be effectively utilised in the synthesis of copper(i) nitride, Cu3N, powders and films by combinations of wet processing and gas-solid (ammonolysis) techniques. The resulting materials were characterized by powder X-ray diffraction (PXD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), diffuse reflectance UV-visible spectroscopy (DRUV-Vis), Raman spectroscopy, infrared spectroscopy (IR), thermogravimetric-differential thermal analysis-mass spectrometry (TG-DTA-MS) and nitrogen adsorption (BET) analysis. Moreover, variable temperature IR (VT-IR) studies of the solid phase were performed in situ during ammonolysis. Single-phase Cu3N powders composed of sub-micron scale platelets can be produced over relatively short reaction times. Materials prepared in this way are stoichiometric narrow band gap semiconductors. The same trifluoroacetate precursor was used to prepare nanostructured nitride films by spin coating. The surface microstructure was investigated and evaluated relative to films deposited by dip coating and nebulisation using the soluble carboxylate precursor.
Reactive magnetron sputtering using an alloy TiCu target and nitrogen as working gas was utilized to deposit ternary (Ti,Cu)N thin films. The aim of present work is to provide insight into the significance of nitrogen pressure, Ti addition, reflected neutral particles and energy flux on the characteristic of (Ti,Cu)N films.
The ion induced secondary electron emission and surface poisoning of TiCu target were studied using I- V characteristic of magnetron discharge. The dependence of sputtering yield of Cu, Ti and TiCu target on incident angle of ions was simulated. Elemental titanium to copper (Ti:Cu) ratio in (Ti,Cu)N films was estimated using a model based on sputtering and mass transport. An estimation of energy flux due to reflected N neutrals toward substrate was presented. The structural analysis was identified using X- ray diffraction (XRD) technique. Phase identity is strongly depending on nitrogen pressure. Ti accommodation to Cu3N structure results in lattice constant expansion and (100) preferential orientation (texture growth). The Bonding environment of pure and Ti inserted Cu3N thin films were obtained from Raman spectroscopy. The Surface morphology and chemical composition of the films were studied by scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX), respectively. Ti addition deforms pyramidal- like grains to spherical ones. The optical study was performed by UV- Vis- near IR transmittance spectroscopy. Ti addition to Cu3N structure kills indirect semiconducting transition and governs the direct bandgap around 2.75 eV. Ti entrance results in interstitial N excess (N-richness) which acts as acceptor centers cause to hole injection to valence band (excited semiconductor) and bandgap widening. Electrical resistance of (Ti,Cu)N thin films shows quasi-metallic behavior. Grain boundary sliding causes to decrease in hardness of (Ti,Cu)N thin films.
Thin films of ternary compounds CuxInyN were grown on Si (100) wafers by RF magnetron cosputtering at a low temperature, low power and pure N2 environment. The effect of In incorporation on the structure and physical properties of copper nitride was obvious, which was evaluated by characterizing the film chemical bonding state, structure, electrical and optical properties. In XPS, shift of binding energy, Auger peak and Auger chemical parameters all reflected the chemical changes in the environment. For samples with In content below 8.2 at.%, either the BE increasing of Cu 2p3/2 and In 3d5/2 or the decreasing of N1s could mainly contribute to the Cu-In-N bond formation. For the Cux InyN sample with 4.6% In, indium atoms were consistently confirmed to be incorporated into the body center of Cu3N anti-ReO3 structure as shown by XRD and TEM. The strong (001) preferred orientation of copper nitride crystalline phase was kept predominant in the films until the In content goes up to 10.8 at.%, the texture changed to (111) orientation. The R-T curves of CuxInyN films changed from typical exponential to linear with increasing In. Near constant electrical resistivity in a large temperature range with small TCR of -6/10000 was investigated in the CuxInyN sample with 47.9 at.% In. Moreover, the optical band gap, due to Burstein-Moss effect, was investigated to enhance from 1.02 to 2.51 eV with the In content increasing from 0% to 26.53%, accompanied with band-gap transition from direct to indirect.
Cu3N is a semiconductor with a bandgap of ∼1.4 eV, which is ideal for solar energy conversion applications. To obtain high-efficiency Cu3N-based solar cells, the fabrication of p-n homojunctions is desirable. Studies on the bipolar doping of Cu3N have been initiated very recently. In this study, we demonstrate that lithium-insertion into p-type Cu3N films using a soft chemical treatment causes a p- to n-type conversion and nonmetal-metal transition. This lithium insertion was achieved by treating p-type Cu3N films with n-butyllithium solutions at moderate temperatures of 313-343 K, such that the lithium atoms diffused into Cu3N and occupied the vacant interstitial sites of the crystalline lattice. As a result, the lithium-inserted Cu3N (LixCu3N) films became n-type semiconductors, indicating that the lithium atoms act as electron donors. Moreover, LixCu3N films with x > 0.05 were found to show metallic electrical conductivity with resistivities of (2-4) × 10-3 Ω cm. This metallic behavior was also observed in the optical transmittance and reflectance data. The findings of this study allowed us to prepare p-type, n-type, and metallic Cu3N-based films. These results may pave the way for the realization of nontoxic wholly Cu3N-based homojunction solar cells delivering high performance.
V-doped Cu3N films were prepared successfully by magnetron sputtering under the experiment condition. XRD shows that the Cu3N film growth prefers direction by changing from (111) to (100) direction with increasing the content of V. SEM shows that the grains' shape of Cu3N crystals has been changed by inserting V atoms into the film. Moreover, the optical absorption, electric conduction and mechanical property of the Cu3N films have been better by doping V to the films.
This work investigates the formation of a Cu3Au-nitride alloy using experimental and computational methods. For this purpose, we prepared a custom-made Cu-Au target and then hit it with argon ions in the presence of molecular nitrogen that produced a film on Corning glass. This film was analyzed using spectroscopic and diffraction techniques. The four-point-probe method and Tauc plots were applied to determine the electrical and optical properties of this thin film. Using first principle calculations a structural model was constructed that validated our observations. The crystalline system that we used was cubic (Pm3m space group) with half the sites filled with Au randomly. The composition was close to Cu3Au0.5N. In agreement with the electrical measurements and calculations, the Cu3Au0.5N band structure was highly affected by the Au incorporation since the electrical resistance and carrier density were in the 10-3 Ω cm and 1022 cm-3 ranges, respectively, and the optical gap decreased 0.61 eV with respect to the Cu3N. The material was a pseudo-gap conductor with conductance as good as a heavily-doped semiconductor at room temperature; this should give it great potential for use in the optoelectronics industry.
Copper nitride (Cu3N) and Fe-, Co-, and Ni-doped Cu3N films were prepared by reactive magnetron sputtering. The films were deposited on silicon substrates at room temperature using pure Cu target and metal chips. The molar ratio of Cu to N atoms in the as-prepared Cu3N film was 2.7: 1, which is comparable with the stoichiometry ratio 3: 1. X-ray diffraction measurements showed that the films were composed of Cu3N crystallites with anti-ReO3 structure and adopted different preferred orientations. The reflectance of the four samples decreased in the wavelength range of 400-830 nm, but increased rapidly within wavelength range of 830-1200 nm. Compared with the Cu3N films, the resistivity of the doped Cu3N films decreased by three orders of magnitude. These changes have great application potential in optical and electrical devices based on Cu3N films. (C) 2014 American Vacuum Society.
A new ternary solid solution, Cu3-xNix+yN, is prepared by gas-pulsed CVD at 260 °C. Gas pulses of the precursor mixtures Cu(hfac)2 + NH3 and Ni(thd)2 + NH3, separated by intermittent ammonia pulses, are employed for the deposition of Cu3N and Ni3N, respectively. A few monolayers of the nitrides are grown in each CVD pulse and then mixed by diffusion to produce the solid solution. The metal content of the solid solution can be varied continuously from 100% to about 20% Cu, which means that the electrical properties can be varied from 1.6 eV (band gap of Cu3N) to metallic (Ni3N). This is of interest for various applications, e.g., solar energy, catalysis, and microelectronics.
This study investigated the formation of a Cu3Au-nitride alloy using both experimental and computational methods. The alloy was produced as thin film by sputtering a Cu3Au target in a nitrogen atmosphere. The films were characterized for structure and composition by spectroscopic and diffraction techniques. The structure was established by Rietveld and ab inito methods. The structure is cubic and of the Fm3m space group, with a composition close to Cu6AuN2. Relative to the Cu3N structure, the Cu atoms occupy the faces, Au the half corners, and N the centers. The compound is a narrow-gap semiconductor with a positive hall coefficient that could be used for infrared detection.
A sintered Ti13Cu87 bi-component target was sputtered by reactive DC magnetron sputtering in nitrogen ambient under various sputtering powers. Ti included Cu3N (Ti:Cu3N) thin films were deposited on Si (1 1 1), KBr (potassium bromide), quartz and glass slide substrates. Crystalline phases of the films were identified by X-ray diffraction (XRD) technique. Crystalline quality and phase stability are strongly dependent on sputtering power. Formation of copper vacancies in Cu 3N cell substituted by Ti atoms and subsequent excess of interstitial nitrogen (N-rich) result in lattice constant expansion. Bonding environment in these films was obtained from fourier transform infrared (FTIR) spectroscopy. Surface morphology of the films that were studied by a scanning electron microscope (SEM) indicates a granular structure. Atomic Ti:Cu ratio of Ti:Cu 3N films, determined by energy dispersive X-ray (EDX) spectroscopy, is less than that of original target. Optical study was performed by Vis-near IR transmittance spectroscopy. Film thickness, refractive index and extinction coefficient were extracted from the measured transmittance using pointwise unconstrained minimization approach. The TiCu 3N films are direct semiconductor with bandgap energy with the range of 2.79–3.34 eV. Ti incorporation and subsequent N-rich have a significant role in bandgap widening and lattice constant expansion. The films electrically show quasi-metallic behavior.
Pd-doped copper nitride films with Pd concentrations up to 5.6 at. % were successfully synthesized by reactive magnetron sputtering of metal targets. Higher concentration of Pd (>5.6 at. %) would deteriorate the quality of the deposits. XPS and XRD data strongly suggest that Pd atoms occupy the centers of the Cu3N unit cells rather than simply substituting for the Cu atoms. A reduction in the electrical resistivity by three orders of magnitude was observed when the Pd concentration increases from zero to 5.6 at. %. All the deposits with the Pd concentration up to 5.6 at. % exhibit n-typed conductivity behavior. The corresponding carrier concentrations increase by four orders of magnitude from 1017 to 1021 cm−3. Compared with the undoped copper nitride films, a weakly Pd-doped Cu3N films possess fine thermal stability in vacuum. And the decomposition product after annealing at 450 °C exhibits a good metallic behavior, indicating that it qualifies the fabrication of conduct wires or metallic structures for the promising applications.
We have studied the structural properties of the clean (0 0 1) surface of Cu3N in the anti-ReO3 structure (space group Pm3m) using Density Functional Theory (DFT). We found that a small relaxation occurs: the first interlayer distance is contracted by ∼1.4%, while the second one is expanded by 0.55%. We have also investigated the adsorption of Pd on the (0 0 1)-Cu3N surface and determined the energy barriers for lateral diffusion in the topmost layer. The incorporation of Pd atoms into the bulk was also considered by calculating adsorption sites and energy barriers. It is found that the most stable configuration corresponds to the Pd atom occupying the center of the cube. To arrive to this site, the atom has to overcome an energy barrier of 0.78 eV. This configuration is more stable than adsorption of the Pd atom on the surface.
Copper nitride films were deposited on glass substrates by reactive DC magnetron sputtering at 100 °C substrate temperature. The influence of N2-gas flow rates on the structure, resistivity and microhardness of deposited films was investigated. X-ray diffraction measurements showed that the films were composed of Cu3N crystallites with anti-ReO3 structure and exhibited preferential orientation to the [111] and [100]. The preferred crystalline orientation of the films changed with the N2-gas flow rate, which should caused by the variation of Cu nitrification rate with N2-gas flow rate. Additionally, the N2-gas flow rate also affected the deposition rate, the resistivity and the microhardness of the Cu3N films. The optimum N2-gas flow rate for producing high-quality and well-oriented Cu3N films on glass substrates is 5–10 sccm, where the substrate temperature is 100 °C and the DC power is 50 W.
A growth stability diagram for the CuNO system has been determined in the temperature range 250–500 °C for a thermally activated CVD process, based on copper (II) hexafluoroacetylacetonate (Cu(hfac)2), NH3 and H2O. Without any addition of water only Cu3N was obtained. Addition of water introduces oxygen into the Cu3N structure to a maximum amount of 9 at% at a water/nitrogen molar ratio of 0.36 at 325 °C. Above this molar ratio Cu2O starts to deposit, in addition to an oxygen doped Cu3N phase. Only Cu2O is deposited at large excess of water.XPS and Raman spectroscopies indicated that the additional oxygen in the doped Cu3N structure occupies an interstitial position with a chemical environment similar to that of oxygen in Cu2O. The oxygen doping of the Cu3N phase did not influence the lattice parameter, which was close to the bulk parameter value of 3.814Å. The film morphology varied markedly with both deposition temperature and water concentration in the vapour during deposition. Increasing the water concentration results in less faceted and textured films with smoother and more spherical grains. The resistivity of the Cu3N films increased with increased oxygen content of the film and varied between 10 and 100 Ω cm (0–9 at% O). The optical band gap increased from 1.25 to 1.45eV as the oxygen content increased (0–9 at%).
Nanocrystalline Cu3NZnx compound films were synthesized using reactive magnetron sputtering of metal targets. Up to a Zn content of 5.44 at.%, the deposits exhibit a satisfactory crystallinity that the X-ray diffraction patterns show distinct (0 0 1) and (0 0 2) reflections characteristic of the intrinsic Cu3N lattice. The slightly enlarged lattice constant suggests insertion of zinc atoms to the center of cells of primitive Cu3N lattice. All the ternary deposits exhibit an n-typed conductivity. Electrical resistivity at room temperature drops by three orders of magnitude with increasing zinc concentration from 0 to 5.44 at.%, and accordingly the activation energy for electrical conduction decreases from 21.9 to 14.1 meV, indicating the presence of shallow donor levels in doped samples. The electronic transport is governed by thermal activation in lightly doped samples, whereas in samples with a zinc concentration of 5.44 at.% or higher it is instead dominated by a hopping mechanism at low temperatures (<50 K).
A sintered Ti13Cu87 target was sputtered by reactive direct current (DC) magnetron sputtering with a gas mixture of argon/nitrogen for different sputtering powers. Titanium-copper-nitrogen thin films were deposited on Si (111), glass slide and potassium bromide (KBr) substrates. Phase analysis and structural properties of titanium-copper-nitrogen thin films were studied by X-ray diffraction (XRD). The chemical bonding was characterized by Fourier transform infrared (FTIR) spectroscopy. The results from XRD show that the observed phases are nano-crystallite cubic anti rhenium oxide (anti ReO3) structures of titanium doped Cu3N (Ti:Cu3N) and nano-crystallite face centered cubic (fcc) structures of copper. Scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM/EDX) were used to determine the film morphology and atomic titanium/copper ratio, respectively. The films possess continuous and agglomerated structure with an atomic titanium/copper ratio (~ 0.07) below that of the original target (~ 0.15). The transmittance spectra of the composite films were measured in the range of 360 nm to 1100 nm. Film thickness, refractive index and extinction coefficient were extracted from the measured transmittance using a reverse engineering method. In the visible range, the higher absorption coefficient of the films prepared at lower sputtering power indicates more nitrification in comparison to those prepared at higher sputtering power. This is consistent with the formation of larger Ti:Cu3N crystallites at lower sputtering power. The deposition rate vs. sputtering power shows an abrupt transition from metallic mode to poisoned mode. A complicated behavior of the films' resistivity upon sputtering power is shown.
Copper nitride (Cu3N) thin films were prepared on glass substrates by reactive radio-frequency (RF) magnetron sputtering under different nitrogen flow rate. The thermal stability of the Cu3N films was investigated through vacuum annealing treatment at different temperature. X-ray diffraction, scanning electron microscopy and near-normal reflectance spectra were employed to characterize the films. The deposited Cu3N films take on a different preferred orientation, which changed from (111) to (100) with increase of N2 ratio. The grains size of thin films can become small when the N2 ratio increases. The Cu3N phase can completely decompose into Cu and N2 through vacuum annealing treatment at a temperature of 200°C. The reflectance of as-deposited Cu3N films is quite different from decomposed films.
. Cu3N films for optical data storage were deposited on Si(100) wafers and 0.6 mm thick polycarbonate DVD base material discs at
a temperature of 50 °C by reactive magnetron sputtering. A copper target was sputtered in rf mode in a nitrogen plasma. For
basic investigations concerning the composition and structure of Cu3N, Si wafers were used as substrate material. To study the suitability of Cu3N as an optical data storage medium under technical conditions, Cu3N/Al bilayers were deposited on polycarbonate discs. The composition and structure of the films were investigated by X-ray
photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).
The decomposition of Cu3N into metallic copper and nitrogen was induced and characterized with a dynamic tester consisting of an optical microscope
with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity
photo detector. Optimized Cu3N films could be decomposed into metallic copper at pulse lengths of 200 ns. The reflectivity change from 3.2% to 33.2% for
completely transformed areas and to 12% for single bits as well as the maximum write data rate of 3.3 Mbit/s demonstrated
the suitability of Cu3N for write once optical data storage. Especially the carrier to noise ratio of 41 dB shows an increase of a factor of 3 for
this novel material as compared to conventional optical data storage media.
Copper nitride Cu 3 N thin films were deposited on glass substrates by reactive radio-frequency magnetron sputtering of a pure copper target in a nitrogen/argon atmosphere. The deposition rate of the films gradually decreased with increasing nitrogen flow rate. The color of the deposited films was a reddish dark brown. The Cu 3 N films obtained by this method were strongly textured with crystal direction 100. The grain size of the polycrystalline films ranged from 16 to 26 nm. The Hall effect of the copper nitride Cu 3 N thin films was investigated. The optical energy gap of the films was obtained from the Hall coefficient and found to vary with the nitrogen content. The surface morphology was studied by scanning electron microscopy and atomic force microscopy. The copper nitride thin films are unstable and decompose into nitrogen and copper upon heat treatment when annealed in vacuum with argon protected at 200 °C for 1 h. © 2005 American Institute of Physics.
The Cu 3 N films were synthesized at room temperature by radio frequency magnetron sputtering in various H 2+ N 2 mixture atmosphere on a glass substrate. The introduction of hydrogen promoted the crystallization of Cu 3 N distinctly, and the optimized growth of (100) plane was strong. Compared to the films with no hydrogen introduced, the electrical resistivity decreased by several magnitudes and the optical energy gap decreased notably too. A conspicuous improvement of electrical and optical properties was achieved, but the surface morphology did not gain any modification; on the contrary, the introduction of hydrogen engendered the protuberances on the surface of the films. The thermal stability was investigated by heating the films in vacuum chamber at different temperatures. The films decomposed at 150 ° C initially and at 250 ° C entirely; the thermal stability is not as good as Cu 3 N films with no hydrogen included. The films were characterized by x-ray diffraction, UV-visible spectrum, four-point probe, and field emission scanning electron microscope method.
Selected covalent metal nitrides with limited thermal stability, such as Sn3N4, Cu3N, and Ni3N, were prepared in a glow discharge system by reactive sputtering in a nitrogen plasma. These compounds were characterized by chemical analysis and their thermal behavior established by temperature-programmed thermal decomposition. These materials decompose into the elements with the rate reaching a maximum at 615, 465, and 405 °C for Sn, Cu, and Ni respectively. The feasibility of using these coatings to generate metal lines by maskless laser writing is explored. Conducting metal lines, a few micron in width, could be generated with each of these nitrides. The resistivities of the metal lines were within an order of magnitude of those of the bulk metals for Cu and Ni and somewhat more for Sn.
Copper nitride films were prepared by the rf magnetron sputtering method using Ar and N2 as working gas. The nitrification degree of the films was studied by changing the N2 fraction or the substrate temperature under the N2 fraction of 30%. The films deposited under different N2 fraction were also annealed at temperature range of 100–300°C in order to study the thermal stability of the films. X-Ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the films. It was shown that the films grow along the [100] orientation and the preferential growth becomes heavier with increasing N2 fraction. The size of the Cu3N grain is estimated to be on the order of nanometers, and the grain size increases with increasing N2 fraction. The Cu3N phase is thermally unstable in vacuum even at 100°C. During the deposition under the N2 fraction of 30%, the highest substrate temperature to form the Cu3N phase ranges from 200 to 250°C. Good agreement between XRD and XPS analysis was obtained in characterizing the film structures. The observed phenomena are discussed briefly.
We have performed accurate ab initio total energy calculations using the full-potential linearized augmented plane wave (FP-LAPW) method to investigate the structural and electronic properties of copper-transition metal nitrides. In its ground state, Cu3N crystallizes in an anti-ReO3 type cell and it is a semiconductor material with a small indirect gap. In this paper, we report a study of Cu3MN compounds with M = Ni, Cu, Zn, Pd, Ag, and Cd. In the calculations, we have used the same anti-ReO3 type cell of Cu3N, but with the extra transition metal atom at the center of the cube. In particular, our calculated lattice parameters for copper nitride (a = 3.82 Å) and copper palladium nitride (a = 3.89 Å) are in excellent agreement with the experimental values of a = 3.807 Å and a = 3.86 Å, respectively. In all the cases we have studied, the addition of the transition metal atom modifies the electronic structure of Cu3N, turning all copper-transition metal nitrides into metals.
Compositions and structures of sputter-deposited Cu–N films are strongly dependent on the total sputtering pressure and on the content of nitrogen gas. The Cu–N films obtained can be classified into four categories: metallic Cu-rich Cu3N films with a positive temperature coefficient of resistivity (TCR), semiconducting Cu-rich Cu3N films, semiconducting stoichiometric Cu3N films, and semiconducting N-rich Cu3N films with a negative TCR. The current–voltage curves of various Cu–N films are presented. The metallic conduction and semiconductor conduction are two main electrical conduction mechanisms for various Cu–N films. The decomposition temperature of various Cu–N films has been determined to be around 604–614 K using both thermogravimetry and dynamical measurement of electrical resistance during heating in a vacuum furnace. The great scattering of data over the electrical resistivity of Cu3N reported up to now is mainly due to the nonstoichiometry of the Cu3N. The optical band gap of stoichiometric Cu3N is determined to be around 1.8–1.9 eV, but it decreases with the decrease in the degree of stoichiometry. © 1998 American Vacuum Society.
Copper nitride (Cu3N) coatings are deposited on glass and steel substrates by RF magnetron sputtering of a copper target in various Ar–N2 reactive mixtures. The films are characterised by X-ray diffraction, scanning electron microscopy, Vickers microhardness, four-point probe method and UV-visible spectrometry. Nanocrystals of Cu3N are formed as soon as nitrogen is introduced in the deposition chamber. Determination of the Cu3N lattice constant shows that below a critical nitrogen flow rate the films are substoichiometric, and that they are overstoichiometric above this critical flow rate. The nonstoichiometry, the mean crystal size, the direction of preferred orientation and the surface morphology of the films have been correlated. Except for the film deposited with a nitrogen flow rate of 1sccm, the film hardness seems to be independent of this experimental parameter. Finally, the electrical resistivity at room temperature and the optical band gap of Cu3N films have been determined versus the nitrogen flow rate.
Copper palladium nitride phases, Cu3PdxN with x = 0.020 and 0.989, were synthesized by the reaction of [Cu(NH3)2]NO3 with [Pd(NH3)4](NO3)2 in supercritical ammonia at T = 500 °C and P(NH3) ≈ 6 kbar in a temperature gradient of the autoclaves used. X-ray single-crystal investigations led to the perovskite-type structure (“PdxNCu3”) in Pm3m with Z = 1: Cu3Pd0.020(3)N: , , Z(F20) ⩾ 3σ(F20) = 32, N(Var) = 7 Cu3Pd0.989(5)N: , , Z(F20) ⩾ 3σ(F20) = 67, N(Var) = 7Cu3Pd0.020N and Cu3Pd0.989N are silver-coloured electrical conductors. The phases are metastable at room temperature and decompose at 470 °C to give Cu3Pdx and N2.
Copper nitride (CuxN) films were prepared on glass slides by reactive direct current (DC) magnetron sputtering under different nitrogen flow rates and substrate temperature, respectively. X-ray diffraction and reflectance spectra were employed to characterize the films. The CuxN films can completely decompose through heat treatment at temperature as low as 160 °C. The reflectance spectra of the as-deposited films are quite different from that of the decomposed films in a wide wavelength range from UV to infrared. Its relatively low decomposition temperature and large reflectance change before and after decomposition makes it a potential write-once optical recording medium.
Ag–Cu–O films were deposited on glass substrates by reactive magnetron cosputtering of silver and copper targets. In this manuscript, the current applied to the copper target and the oxygen flow rate introduced into the deposition chamber were kept constant, whereas the current applied to the silver target (IAg) was varied. Films deposited without silver crystallised into the paramelaconite structure (Cu4O3). At low silver target current, incorporation of Ag into Cu4O3-based did not modify the film structure. Silver atoms substituted some Cu(+I) atoms leading to the formula: Ag2−xCu2+xO3. On the other hand, when IAg exceeded a critical value, X-ray diffraction analyses revealed a biphased structure: Ag2−xCu2+xO3 and Ag. Contrary to the diffraction peak intensity of the Ag2−xCu2+xO3 phase, that of silver was increased with IAg. For the highest value of IAg, no silver–copper oxide was detected and the mean crystal size of silver grains was close to 2nm. Due to the occurrence of the nanocrystallised silver phase, the film electrical resistivity strongly decreased. Optical reflectance measurements confirmed the structural changes versus the silver target current.
Copper nitride thin films were prepared on glass and silicon substrates by ablating a copper target at different pressure of nitrogen. The films were characterized in situ by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and ex situ by X-ray diffraction (XRD). The nitrogen content in the samples, x=[N]/[Cu], changed between 0 and 0.33 for a corresponding variation in nitrogen pressure of 9×10−2 to 1.3×10−1Torr. Using this methodology, it is possible to achieve sub-, over- and stoichiometric films by controlling the nitrogen pressure. The XPS results show that is possible to obtain copper nitride with x=0.33 (Cu3N) and x=0.25 (Cu4N) when the nitrogen pressure is 1.3×10−1 and 5×10−2Torr, respectively. The lattice constants obtained from XRD results for copper nitride with x=0.25 is of 3.850Å and with x=0.33 have values between 3.810 and 3.830Å. The electrical properties of the films were studied as a function of the lattice constant. These results show that the electrical resistivity increases when the lattice parameter is decreasing. The electrical resistivity of copper nitride with x=0.25 was smaller than samples with x=0.33.
Films of copper (I) nitride were deposited by atomic layer deposition (ALD) using copper (II) hexafluoroacetylacetonate, water, and ammonia as precursors. Introduction of a water pulse in the ALD cycle was found to be crucial for initiating film growth on both amorphous SiO2 and single-crystalline alpha-Al2O3(001) substrates. The water pulses generated an oxidic copper monolayer, which in a subsequent ammonia pulse was converted to the nitride. The films have been grown in the temperature range from 210 to 302 degrees C. Phase pure films of Cu3N were obtained up to 265 degrees C. At higher deposition temperatures such as 283 degrees C, phase mixtures of Cu3N and Cu were obtained. For temperatures above 302 degrees C films of only Cu were grown. Film growth rate was the same on the two different substrates. The films were randomly oriented on SiO2. Completely intact films were obtained at a thickness of 20 nm. The optical bandgap of the films was measured to be 1.6 eV. (c) 2006 The Electrochemical Society.
The copper nitride thin films were prepared on glass substrate by RF magnetron sputtering method. At pure nitrogen atmosphere, the nitrogen flow rate affects the copper nitride thin films’ structures. Only a little part of nitrogen atoms insert into the body center of Cu3N structure and parts of nitrogen atoms insert into Cu3N crystallites boundary at higher nitrogen flow rate. But the indirect optical energy gap, Eopg, decreases with increasing nitrogen flow rate. The typical value of Eopg is 1.57eV. In a nitrogen and argon mixture atmosphere, when the nitrogen partial was less than 0.2Pa at 50sccm total flow rate, the (111) peak of copper nitride appears. Thermal decomposition temperature of Cu3N thin films deposited in pure nitrogen and 30sccm flow rate was less than 300°C. The surface morphology was smooth.
Copper nitride (Cu3N) is a thermally unstable material; therefore both the deposition of a stoichiometric sample and the reliable characterization of its properties constitute a big challenge. We reported here the growth of stoichiometric Cu3N films on Si (1 0 0) wafer by reactive magnetron sputtering of Cu target using pure nitrogen as working gas. At a low substrate temperature (60 degrees C), a combination of high working pressure (> 0.7 Pa) and low RF power supply (< 150 W) favors the formation of stoichiometric deposits. With the pressure at 0.9 Pa and the RF power below 100 W, the deposits are [0 0 1]-oriented and consist of cubic Cu3N grains, which are typically 40 nm in dimension. The lattice constant is 0.383 nm as determined by both X-ray diffraction and transmission electron microscopy; and the electrical resistivity measurement reveals a typical deficit semiconductor behavior in the cubic Cu3N. The thermal decomposition temperature, being reported within 100-470 degrees C, was determined to be similar to 350 degrees C as indicated by the presence of Cu (1 1 1) and (0 0 2) reflections after prolonged annealing. (c) 2006 Elsevier B.V. All rights reserved.
We have studied the structural and electronic properties of bulk copper nitride by performing first principles total energy calculations using the full-potential linearized augmented plane wave (FP-LAPW) method. In our study we have considered two types of cells: the ideal cubic anti-ReO3 structure corresponding to Cu3N, and a unit cell with an extra Cu atom at the center of the cube. In the first case, our calculated lattice parameter a=3.82 Å is in excellent agreement with the experimental value a=3.807 Å. The structure is semiconductor with a small indirect band-gap. The increasing of the lattice parameter results in larger band-gaps. An addition of an extra Cu atom at the center of the cell results in a slightly larger lattice parameter a=3.88 Å, and the structure becomes fully metallic. Our calculated value is similar to the experimental lattice parameter corresponding to a metallic copper nitride film.
Pure and Ti-doped copper nitride films were prepared by cylindrical magnetron sputtering on glass substrates at room temperature. The preferred orientation for copper nitride films changes from [111] for undoped film to [100] for Ti-doped films. The variation of surface morphology correlates to that of preferred orientation resulting from the variation of Ti-doped content. The electrical resistivity and optical band gap increases as the Ti-doped content increases. (c) 2006 Elsevier B.V. All rights reserved.
Copper nitride thin films were prepared by using the ion-assisted
deposition in which accelerated nitrogen ions were irradiated during the
deposition of copper metal. The degree of nitrification of the film was
controlled by changing the ion current density. The reflection
coefficient of the prepared copper nitride films decreased with the
increase of the ion current density. The reflection coefficient was
about 30% at 780 nm wavelength, and it recovered to 70% after the film
was heated at 300°C. The preliminary experiment of write-once
optical recording of this film was carried out, and the viability of its
practical use in new media was confirmed.
Copper, silver, and gold targets were sputtered in various reactive gas mixtures (Ar–N2, Ar–O2, and Ar–CH4) to compare the reactivity of noble metal atoms during the sputtering process. The evolution of the film's growth rate and the variation of the reactive gas partial pressure vs. the reactive gas flow rate were investigated for each kind of metal. The structure of the deposited films was characterised by X-ray diffraction. Electrical resistivity of the coatings was determined at room temperature. The optical band gap of oxides and nitrides films were deduced from UV–visible transmission measurements. The reactive sputtering of copper target leads to the synthesis of Cu3N, Cu2O, Cu4O3, or CuO films. No copper carbide films were deposited. Depending on the methane flow rate, Cu/C films were either nanocomposite coatings (nc-Cu/a-C:H) or amorphous. Silver oxide (Ag2O) films were formed by reactive sputtering of a silver target in Ar–O2 mixtures. On the other hand, the reactive sputtering method did not allow the synthesis of silver nitride nor gold oxide films.
Copper nitride (Cu3N) thin films were prepared on glass substrates by reactive rf magnetron sputtering. The film was decomposed into Cu film by heating 450°C for 30 min. Nitrogen gas effused from the Cu3N film during the heating. The decomposition initiation temperature of the films was about 360°C, and the thermal analysis involved thermogravimetry (TG) as well as a detection of N2+ ion that effused from the films during heating in a vacuum. Electron beam processing was used to decompose Cu3N into Cu. A dot array of μm and μm was obtained on the Cu3N film after electron beam irradiation. The Cu3N films easily dissolved in the dilute HCl solution. The etching rate of the Cu3N film in 100 g/l HCl aqueous solution was 3900 times that of the Cu film.
Copper nitride (Cu3N) films were deposited on glass substrates by sputtering of copper target under various substrate temperatures in the range
303–523K using dc reactive magnetron sputtering. The substrate temperature highly influenced the structural, mechanical,
electrical and optical properties of the deposited films. The X-ray diffraction measurements showed that the films were of
polycrystalline nature and exhibit preferred orientation of (111) phase of Cu3N. The microhardness of the films increased from 2.7 to 4.4GPa with the increase of substrate temperature from 303 to 473K
thereafter decreased to 4.1GPa at higher temperature of 523K. The electrical resistivity of the films decreased from 8.7×10−1 to 1.1×10−3Ωcm and the optical band gap decreased from 1.89 to 1.54eV with the increase of substrate temperature from 303 to 523K
respectively.
Copper nitride thin films were obtained by the reactive sputtering method. A metallic copper target was sputtered in nitrogen gas with radio‐frequency (rf) magnetron sputtering equipment. Highly [100]‐oriented polycrystalline films of the cubic anti‐ReO 3 structure were obtained. Films with a lattice constant above 3.868 Å were conductors, while films with a lattice constant below 3.868 Å were insulators. The resistivity of conducting films was 0.5–3×10-2 Ω cm. The insulating films showed an optical energy gap of 1.3 eV, while the conducting films showed a smaller value which decreased with decreasing resistivity. © 1995 American Institute of Physics.
Thin films of Cu3N were grown on (0 0 1) MgO and (0 0 1) Cu substrates by molecular beam epitaxy of copper in the presence of nitrogen obtained from a radio frequency atomic source. The different aspects of the growth and the properties of the copper nitride films were investigated in relation with growth parameters such as: substrate temperature, growth rate and flux of nitrogen. On MgO substrates, despite a mismatch as high as ∼10%, the Cu3N films grow as epitaxial layers even at room temperature. The upper temperature limit for growth was found to be ∼250 °C. It is likely that the growth mechanism proceeds in a layer-by-layer fashion similar to the growth of γ′-Fe4N layers on MgO substrates using the same growth method. This results in the growth of smooth layers of Cu3N.The films, grown as a pure phase, have a behavior typical for an insulator with an optical gap of 1.65 eV. If a low amount of Cu impurities is present in the Cu3N insulating matrix, the films still have the overall behavior of an insulator, but with a reduced optical band gap. For higher amounts of metal impurities, seen as Cu crystallites in the epitaxial Cu3N phase, the optical band gap reduces even further, and additionally, an extra absorption peak due to Cu appears. The films grown on (0 0 1) Cu substrates, despite the better lattice match, did not show a striking improvement of the crystal quality.
Copper nitride thin films were deposited on silicon wafers by reactive RF magnetron sputtering at various N2-gas partial pressures and substrate temperatures. X-ray diffraction measurements show that the films are composed of Cu3N crystallites with anti-ReO3 structure and exhibit preferential orientation to either the [1 1 1] or [1 0 0] direction at particular N2 pressures and substrate temperatures. The film growth prefers the [1 1 1] direction at the N2 pressures and substrate temperatures below 2.50 mTorr and 150°C, respectively, and the [1 0 0] preference is achieved at 3.75 mTorr and 250°C, respectively. Such preferential film growth is interpreted as being due to the variation of Cu nitrification rate with N2 pressure and substrate temperature. The pseudodielectric function of a Cu3N/Si film was measured by spectroscopic ellipsometry in the 0.8–5.0 eV range. It shows strong Fabry–Perot interference oscillations at low energies due to optical transparency of Cu3N. The fundamental optical band-gap energy of the compound is determined to be 1.5 eV.
The feasibility of using copper nitride and tin nitride thin films as write-once optical recording media was explored. The Cu3N and SnNx films were obtained by the reactive sputtering method. They were thermally decomposed into Cu and Sn films at 470 and 550 °C, respectively. The Cu film obtained by the thermal decomposition showed a large difference in reflectance which is applicable to the optical recording media. The Sn film obtained by the thermal decomposition included SnO, and consequently it showed a small difference in reflectance from that of SnNx film.
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