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Reactive grid-assisted co-sputtering of titanium and chromium in a pure nitrogen atmosphere: Uniformity, optics, and structure of the Ti–Cr–N films
Abstract
This study provides the results of the first attempt to deposit thin films by reactive grid-assisted co-sputtering with the deployment of small grounded grids having two varying apertures for enabling the transfer of particles. The diameter of all the grids utilized was 50 mm, and their apertures' diameters were changed from 5 mm to 15 mm. Furthermore, the ratios of the grid area to the chamber wall area were lower than 0.0161, preventing the formation of ion-rich sheaths and their adverse impact upon discharge and plasma stability. Accordingly, Ti1Cr1-xN films (0.88 < x < 0.97) with low chromium contents were deposited on soda-lime glass substrates by using pure nitrogen as the sputtering gas. The grazing incidence X-ray diffraction patterns of the films, the average thicknesses of which were lower than 50 nm, showed no sign of crystallinity in the films. Ranging from 3.26 to 3.79 eV, the optical bandgap of the films changed by altering the apertures’ size; chromium content, internal stress, and quantum confinement effect appeared to be the main contributing factors. The photoluminescence intensities appertaining to trap state emissions reflected a decreasing trend by increasing the chromium content, which can be ascribed to the capability of the chromium particles included in the surface, structure, and grain boundaries of the films to prevent photoinduced electron-hole pairs from recombination. It was found that not only is the grid-assisted co-sputtering method an effective tool whereby the doping range of conventional co-sputtering methods can be significantly extended but also it can cover a spectrum of surface morphologies. However, in comparison with the conventional co-sputtering method, the utilization of the grids with fairly small apertures can limit the thickness uniformity of the films; this effect may be attenuated by changing the geometry and design of grids.
... To deposit such films, two magnetrons with cold targets [1], a magnetron with a combined cold target [8], or a magnetron with a single pressed target [9,10] are used. Each of these methods has advantages and disadvantages. ...
The purpose of this work is to study the kinetics of the heat flow heating the substrate, which is generated by a two-layer sandwich magnetron target when sputtered in argon. Its novelty resides in the application of the COMSOL Multiphysics to study the kinetics of thermal processes during sputtering of a target of the new type. The analysis was performed for a sandwich target with internal copper and external titanium plates when the discharge power varied in the range of 400–1200 W. The heating of the external target plate is described by a two-dimensional homogeneous Fourier equation. The solution to the equation reveals how the kinetics of the external plate's surface temperature distribution depends on the discharge power. To study the heat flow heating the substrate, the external plate is presented in the form of an additive set of small-sized surface heat sources. Previously unknown features of the thermal process are established. It is shown that numerical modeling adequately describes the experimental results.
... To overcome these problems and improve their properties, binary solid solutions of oxides, nitrides, and others are applied. Examples of these composites are such systems as Ti-Ta-O, 5 Ti-Al-O, 6 Ti-Cr-O, 7 Cr-Al-N, 8 Ti-Cr-N, 9 and Ti-Al-N. 10 These films with conductive, semiconductor, and dielectric properties are widely used in microelectronics, optoelectronics, solar energy, etc. Nitrogen-containing films usually have increased hardness, thermal and chemical resistance; therefore, they can be used to protect the surface of materials in mechanical engineering and the chemical industry. ...
A non-isothermal physicochemical model of reactive sputtering is extended in this work. The new version is used in this work to simulate reactive sputtering of a sandwich target with two plates of different metals located on the same axis. The external plate contains cut-outs through which the internal plate is sputtered. The main independent process parameters are the reactive gas flow introduced into the vacuum chamber, the discharge current density, and the total area of cut-outs in the external plate. The physical model of the process is described by a system containing 14 algebraic equations. Only its numerical solution is possible, which allows studying the sputtering process in detail. The model can be used to estimate the conditions that ensure the deposition of a compound film in a real technological process. The model was used to analyze sputtering of a target with internal titanium and external tantalum plates in oxygen. Application of the model in particular cases of sputtering of single targets showed that it is adequate.
Magnetron sputtering is a very versatile technique extensively employed for the deposition/growth of thin films. However, the deposition of desirable magnetic films is one of the challenges confronting magnetron sputtering owing to the shunting of magnetic flux by magnetic targets in conventional magnetron sputtering equipment. This flux shunting culminates in lower plasma density, non-uniform plasma confinement, and uneven erosion of magnetic targets, adversely affecting the growing films’ thickness uniformity and chemical homogeneity—the latter can be particularly serious in magnetron co-sputtering. In this article, it is discussed that these issues can be avoided by cylindrical sputtering. As for planar sputtering, formerly offered technical solutions including the utilization of thin foils as magnetic targets, the deployment of gapped targets somewhat allowing the magnetic flux of the magnetron assembly, the employment of a target heating system increasing a magnetic target’s temperature greater than or equal to its Curie temperature, facing target sputtering, magnetron sputtering assisted by coupled plasma inductively generated in an internal coil, and the generation of plasma remotely from magnetic targets (i.e., high target utilization sputtering) are scrutinized with their advantages/disadvantages being further examined. Finally, it is discussed that not only can auxiliary grid deployment mitigate/remove the issues of planar magnetron sputtering by modifying spatial plasma density distribution near the target but also it can solely shoulder the responsibility of ionization enhancement and plasma confinement for deposition of magnetic films.
(Ti1-xCrx)N coatings with high corrosion resistance and surface conductivity are developed for Ti bipolar plate. More Cr leads to lower surface conductivity but much higher corrosion resistance. The optimized (Ti0.48Cr0.52)N coating shows a low interfacial contact resistance of 5.1 mΩ cm² at 140 N/cm² and small current density of 0.45 μA/cm² after 10 h corrosion test at 0.2 V vs. Hg/Hg2SO4 (0.5 M H2SO4 + 2 ppm HF, 80 °C with air), which is approximately 50 times lower than that (24 μA/cm²) for TiN. The improved corrosion resistance is majorly owing to the presence of Cr-O-riched bond on the surface.
Transition metal oxides have gained substantial attention in the previous decade by virtue of their distinctive physical and chemical properties. Amidst all, tungsten oxide (WO3) is emerging as distinct metal oxide on account of its outstanding electrochromic performance. Furthermore, optical-switching speed has topmost importance in the actual device. The sole approach to enhance this attribute is to escalate surface area of the electrochromic coatings, which can be done by instigating porosity within bulk material. Porosity can be considered as one of the pivotal facets of functionalized electrochromic thin films. Cations can be made to get transported into the depth of the host with the presence of high porosity in a structure. This featured article is attempting to pivot the path as how porosity is upgrading the electrochromic attribute of WO3 films. Furthermore, various methods to achieve optimum porosity of WO3 films leading to best electrochromic performance are also discussed.
In this paper, the incorporation of auxiliary grids/electrodes into the design of the sputtering method is scrutinized by studying the impact of factors such as grid size, grid position, grid bias voltage, electrode sheath design, substrate bias voltage, reactive gas partial pressure, and magnetic trap configuration on the discharge condition and thin-film growth. In this regard, utilizing the updated Berg model for reactive sputtering, the authors obtained a formulation for the reactive grid-assisted sputtering. By the newly-developed formulation, the sputtering rate and the reactive gas partial pressure were simulated as a function of the reactive gas flow rate for various grid-to-target distances, argon partial pressures (0.67, 1.6, and 3.6 Pa), and discharge current densities (0.01, 0.015, and 0.02 A/cm2). According to the computation results, with a grid being utilized, the width of the hysteresis loops can be modified in a broader range by changing either the grid-to-target distance, the argon partial pressure, or the discharge current, resulting in better control over the deposition process. Moreover, the novel configuration of anode-spot-assisted sputtering was proposed to significantly ionize sputtered/neutral atoms near the substrate and to simultaneously deposit sputtered species and products produced as the direct result of introducing dust into the dense plasma. Finally, diverse configurations of the grid-assisted co-sputtering method were introduced for two prime purposes: deposition of composite films in any desired ratios of constituents without significantly changing the other co-sputtering parameters, and favorable alternation of a hysteresis loop for one of the guns at shared gas flow rates.
In this work, thermal based gas-phase etching of titanium nitride (TiN) is demonstrated using thionyl chloride
(SOCl2) as a novel etchant. A single etchant is utilised in a pulsed fashion to etch TiN. This type of etching
technique may also be considered as a chemical gas-phase or dry etching. The removed TiN amount was
measured by various techniques like spectroscopic ellipsometry (SE), weighing balance and in some cases X-ray
reflectometry (XRR). Additionally, the post-etch surfaces were analysed with X-ray photoelectron spectroscopy
(XPS) and bright field transmission electron microscopy (BF-TEM). The surface roughness and morphology of
before and after etching TiN films were measured using atomic force microscopy (AFM). The etch per cycle (EPC)
was calculated and is plotted as a function of SOCl2 pulse time, purge time after SOCl2 exposure, number of etch
cycles and etch temperature (Tetch). An increase in EPC with an increase in SOCl2 pulse time as well as etch
temperature was observed. SOCl2 is able to etch TiN starting from 270 ◦C with an EPC of about 0.03 Å to almost
1.2 Å at 370 ◦C. Arrhenius plot determined the activation energy (Ea) of about 25 kcal/mol for TiN etching by
SOCl2. In addition, the etch selectivity between different substrates such as silicon dioxide (SiO2), silicon nitride
(Si3N4) and aluminum oxide (Al2O3) was investigated on blanket as well as 3D structures. Moreover, thermodynamic
calculations were performed for various possible etch reactions. Titanium from TiN is proposed to be
etched in the form of either titanium trichloride (TiCl3) or titanium tetrachloride (TiCl4). Nitrogen from TiN films
may form volatile by-products such as diatomic nitrogen (N2), nitrous oxide (N2O) and nitrogen dioxide (NO2).
Titanium nitride (TiN) is an alternative plasmonic material that has the potential for visible and near‐infrared optical applications due to its distinct properties. Here, coupling effects between TiN nanohole array films and nearby excitonic emitters, semiconductor nanoplatelets (NPLs), are investigated using single particle spectroscopy. At the emission wavelength of the NPLs, the local field enhancement close to the surface of the TiN nanohole array films induces an increase in the radiative decay rates of the emitters by a factor of up to 2. This effect diminishes quickly as the distance between the TiN nanohole array films and emitters increases. At short wavelengths where the NPLs are excited, the TiN nanohole array films exhibit lossy dielectric characteristics. Local field modification at these wavelengths leads to a reduced local density of electromagnetic states, and hence the photoluminescence intensity of the emitters. This study shows the potential of TiN as an alternative plasmonic material for optoelectronic and photonic applications, especially in the long wavelength ranges. Titanium nitride as an alternative plasmonic material is investigated by coupling its thin films to emitters. Local field modifications lead to changes in the radiative decay rates and emission intensities of the emitters, both dependent on the distance between the emitters and the titanium nitride thin films. This work indicates the potential application of titanium nitride in optoelectronic devices.
Extremely thin, Al–Zn–O composite films (21 ± 6 nm) are deposited on fused silica substrates under various percentages of oxygen in the oxygen/argon gas mixture (3%, 4.5%, 6%, and 7.5%). The films are prepared by a cylindrical DC magnetron sputtering system, utilizing a single compound target. The effects of the oxygen percentage on the compositional, morphological, and optical properties of the films are investigated by energy‐dispersive X‐ray spectroscopy, scanning electron microscopy, UV‐visible spectrophotometry, and atomic force microscopy. The chemical composition of the films is Al1 Zn1+X O with 0.2 < X < 1. The average visible transmittance of 93.6% with a high level of uniformity is obtained when the sputtering deposition performs under the oxygen percentage of 6%. It is found that the optical band gap of the films can be tailored toward higher energy by increasing oxygen percentage; however, the adjustable range is not so significant. The results offer cost‐efficient films with high, uniform transmittance in the visible region and with an ability to attenuate more than 10% of incident UV‐B radiation (280‐315 nm). This type of films can potentially be included in greenhouse screen systems to effectively protect the plants from the elevated UV‐B radiation without altering natural conditions.
Overcoming the challenge of growing ultrathin metallic films is of great importance for practical applications of nanoplasmonic structures. In the present work, epitaxial, ultrathin (<10 nm) films of plasmonic TiN are grown on MgO using DC reactive magnetron sputtering. The optical properties of the films are studied through variable angle spectroscopic ellipsometry and Hall measurements. As the film thickness decreases, they become less metallic and exhibit higher loss while still remaining plasmonic in the optical range. These trends are related to the decreasing carrier concentration in the thinner films and increased scattering, respectively. However, all films tested (2, 4, 6, 8, and 10 nm) still remain highly metallic with a carrier concentration on the order of 1022 cm−3. Based on the relationship between the plasma frequency, carrier concentration, and effective mass, it is determined that the reduction in carrier concentration plays the main role in defining the film's optical properties, as variations in the effective mass are found to be minimal for thicknesses above 4 nm. However, for the 2 nm film and below, theoretical calculations begin to deviate from experimental values.
Nano-crystalline Titanium Nitride (TiN) thin films were deposited on glass substrates by reactive DC magnetron sputtering in the presence of a supported discharge (dc triode magnetron sputtering). A hot thermionic filament which was negatively biased is kept between the target and substrate, and was used to sustain the discharge at much lower pressures. The TiN films deposited at room temperature (RT) were annealed at different temperatures of 373, 473 and 573 K in a high vacuum for 1 h. The films were characterized for their morphological, structural, micro-structural, optical and electrical properties. RT deposited titanium to nitrogen ratio was found to be 1:1 which has been confirmed by EDAX. XRD studies showed that the as-deposited TiN thin film were amorphous in nature and transformed to a nano-crystalline structure with increasing annealing temperatures. The crystallite growth of TiN thin films started around 373 K onwards, and it became a face-centered cubic structure with a preferred orientation along the (111) plane. The band gap of TiN thin films was found to increase from 2.7 to 3.2 eV with an increase in the annealing temperature. The photoluminescence spectrum of TiN thin films indicates a broadening of emission wavelength in the visible region with a maximum emission peak around 360 nm. The electrical resistivity of TiN thin films was found to drop significantly from 1800 to 400 µΩ cm with an increase in the annealing temperature. The AFM micrographs of annealed TiN thin films show uniform surface pattern associated with a large accumulation of fine grains. Through this work, it has been demonstrated that it is possible to achieve the required physical properties of TiN films at lower annealing temperatures by the supported discharge dc magnetron technique compared to other sputtering techniques.
ZnO thick Stress relaxed films were deposited by reactive magnetron sputtering on 2”-wafer of SiO2/Si at room temperature. The residual stress of ZnO films was measured by measuring the curvature of wafer using laser scanning method and found in the range of 0.18 x 109 to 11.28 x 109 dyne/cm2 with compressive in nature. Sputter pressure changes the deposition rates, which strongly affects the residual stress and surface morphologies of ZnO films. The crystalline wurtzite structure of ZnO films were confirmed by X-ray diffraction and a shift in (0002) diffraction peak of ZnO towards lower 2θ angle was observed with increasing the compressive stress in the films. The band gap of ZnO films shows a red shift from ∼3.275 eV to ∼3.23 eV as compressive stress is increased, unlike the stress for III-nitride materials. A relationship between stress and band gap of ZnO was derived and proposed. The stress-free growth of piezoelectric films is very important for functional devices applications.
As the size of a positively biased electrode increases, the nature of the interface formed between the
electrode and the host plasma undergoes a transition from an electron-rich structure (electron sheath)
to an intermediate structure containing both ion and electron rich regions (double layer) and ultimately
forms an electron-depleted structure (ion sheath). In this study, measurements are performed to further
test how the size of an electron-collecting electrode impacts the plasma discharge the electrode is
immersed in. This is accomplished using a segmented disk electrode in which individual segments are
individually biased to change the effective surface area of the anode. Measurements of bulk plasma parameters
such as the collected current density, plasma potential, electron density, electron temperature
and optical emission are made as both the size and the bias placed on the electrode are varied. Abrupt
transitions in the plasma parameters resulting from changing the electrode surface area are identified
in both argon and helium discharges and are compared to the interface transitions predicted by global
current balance [S. D. Baalrud, N. Hershkowitz, and B. Longmier, Phys. Plasmas 14, 042109 (2007)].
While the size-dependent transitions in argon agree, the size-dependent transitions observed in helium
systematically occur at lower electrode sizes than those nominally derived from prediction. The discrepancy
in helium is anticipated to be caused by the finite size of the interface that increases the effective
area offered to the plasma for electron loss to the electrode
Room-temperature ferromagnetic In1−xCrxN films with x ranging from 0.0005 to 0.04 and antiferromagnetic CrN films have been grown by plasma-assisted molecular-beam epitaxy. Electron and x-ray-diffraction techniques could find no evidence for precipitates or phase segregation within the films. Ferromagnetism was observed in the In1−xCrxN layers over a wide range of Cr concentrations, with the magnitude of the ferromagnetism found to correlate with the background carrier concentration. Higher n-type carrier concentrations were found to lead enhanced ferromagnetism, with maximum saturation and remnant moments of 7 and 0.7 emu/cm3, respectively. The addition of Cr to the InN matrix led to reduced photoluminescence intensity and a shift of the peak to higher energy. These observations along with a band-gap-like optical transmission feature at 0.7 eV suggest that CrN has an indirect gap of approximately 0.7 eV and a direct Γ-valley gap greater than 1.2 eV.
Nanocrystalline titanium nitride thin films have been deposited by reactive dc magnetron sputtering in pure N2, Ar–N2 and He–N2 gas mixtures. The influence of the nature of the sputtering gas on the structural, optical and the electronic properties of the nanocrystalline TiN films has been studied. Structural properties were investigated by using x-ray diffraction and an atomic force microscope, optical ones by using a UV–visible spectrophotometer and electronic properties by means of dc four-probe resistivity measurements. The films deposited in an He–N2 gas mixture exhibited a strong (111) texture, while for those deposited in an Ar–N2 mixture under identical conditions, the texture of the films changed from (111) to (200).
ZnO thin lms were successfully deposited onto PET substrates prepared by using cathodic arc plasma deposition (CAPD) technique at a low temperature (<75 degrees C). Their structure, optical and electrical properties were investigated with various arc currents (40, 45, 50 and 55 A). ZnO (0 0 2) peak was clearly observed, and increased as the arc current increased from 40 A to 55 A. The calculated average crystallized sizes were around 15.9-17.7 nm. The films have an average transmittance over 85% in the visible region, and calculated values of the band gap around 3.33-3.31 eV with increase of the arc current. It was also found that a slight blue shift of optical transmission spectra was observable when decreasing the arc current. The deposited ZnO films had the lowest resistivity; about 3 x 10(-3) Omega cm for the ZnO lm with the arc current of 40 A. Crown Copyright
This work aimed to develop an efficient lubricant for physical vapor-deposited TiN coatings on steel by adding cyclopropane-carboxylic acid (CPCa) to PAO4 base oil to enhance boundary lubrication. Results showed that an ultralow coefficient of friction (0.008) and wear rate (7.0×10⁻⁸ mm³/N∙m) were obtained for the steel/TiN sliding contact using PAO4+2.5 wt % CPCa oil due to the in situ formation of a carbon-based lubricating tribofilm during the sliding process.
Al-doped ZnGa2O4 (ZGO) films were deposited on c-plane sapphire substrates by co-sputtering of Al and ZGO targets at a substrate temperature of 400 ℃ and thermally annealed at 800 ℃ to enhance their crystalline quality. In this investigation, the DC power for metallic Al target was varied from 0 to 50 W and its effect on structural, optical, and optoelectronic properties of these films were investigated. After annealing, all films exhibited the crystalline nature with the ZGO phase. Further, this investigation revealed that the 800 ℃ annealed Al-doped ZGO film deposited with the 20 W DC power possessed the highest crystalline quality among other films along with the wide-bandgap of 5.18 eV. The X-ray photoemission spectrum measurements revealed from the Ga 2p3/2 and Al 2p core-level spectra that the Al atoms occupy the octahedral sites, which makes Al─O─Ga bonding in the ZGO network. The metal-semiconductor-metal photodetector with this annealed 20 W Al-doped ZGO film exhibited the photocurrent to the dark current ratio of 3.35 x 10⁴ and high responsivity of 3.01 A/W (at 3 V and 220 nm), which shows the enhancement in device performance about 12 times when compared with that of annealed 0 W Al-doped ZGO photodetector.
Titanium nitride (TiN) is widely used in electrode materials in fast charging/discharging supercapacitors (SCs) due to its outstanding conductivity. However, the low capacitance of the TiN electrode limits its further application in the SCs. Therefore, the reasonable design of the TiN electrode with high electrochemical and mechanical properties is still a challenge. In this paper, the silicon nanowires/titanium nitride electrode (Si NWs/TiN) is prepared by depositing TiN onto the etched Si nanowires by direct current magnetron sputtering. The Si NWs are prepared by etching silicon in 4.8 M HF/0.02 M AgNO3 aqueous solution for different times (5 min, 15 min, 30 min, 60 min). The mechanism of the effect of etched silicon substrate morphology on the electrochemical performance of Si NWs/TiN electrode was studied. As the etching time increases, the differences of the TiN surface structure, lattice defects and surface chemical composition will change the capacitance performance and charge storage mechanism of the Si NWs/TiN electrode. The prepared Si30 NWs/TiN electrode exhibits an outstanding specific capacitance as high as 113.55 F g⁻¹ at a scan rate of 5 mV s⁻¹ with 0.5 M H2SO4 solution as electrolyte. The specific capacitance of the Si30 NWs/TiN electrode is as high as 7.5 times that of the electrode without etching at 100 mV s⁻¹. The Si30 NWs/TiN electrode has an excellent cyclic stability performance, which the electrode has a decay rate of 12.4% after 2000 cycles. This indicates that the electrode has reliable stability. The electrode of the supercapacitor prepared by this method can open up a new way to expand the specific surface area of other transition metal nitride.
High entropy ceramics (HECs) films (TiCrZrVAl)N were deposited on Inconel 718 alloys by multi-arc ion plating (MAIP) equipment at different nitrogen flow ratios Rn=N2/(N2+ Ar). The effects of Rn (0%, 20%, 50%, 80%,90%) on the evolution of microstructure, mechanical properties, and tribological properties of films were systematically studied. The films deposited at low Rn exhibited an amorphous structure and smooth cross-section, whereas the films at Rn of 50% and higher showed a face-centered-cubic (FCC) NaCl-type structure with loose columnar cross-section. With the increase of Rn, the content of the N element increased, the Cr element decreased, and other elements (Ti, Zr, V, Al) nearly remained stable. The films' hardness and elastic modulus increased gradually and reached the maximum value of 31.08±1.81 GPa and 387.66±12.49 GPa, respectively, when Rn was 80%. The films deposited at Rn of 20% invalided easily in tribology tests, whereas the films prepared under Rn exceeded 20% presented outstanding wear resistance and obtained the minimum wear rate of 7.4×10⁻¹⁶ m³/(N·m) when Rn is 80%.
In the present study, the influence of structured capillary-porous coatings of surface on cryogenic quenching by the falling liquid nitrogen film is investigated. The coating was produced by the directional plasma spraying technique. The cryogenic quenching experiments were performed on high-temperature vertical copper slab with bare surface and on the surfaces with different orientation of coating protrusions. Thermocouples and a high-speed digital video camera were employed to obtain a synchronized data on the temperature-time history of the transient process and the pattern of quench front propagation. The peculiarities of quench front dynamics and heat transfer in the transient process are studied. The created numerical model determines the quench front velocity and the temperature fields in the heater, varying in space and time. The dynamic pattern of quench front propagation obtained numerically satisfactorily correlates with the observed in the experiments one. The heat transfer curves during quenching were determined for different surfaces based on the experimental cooling thermograms and visualization data. The results show that the cooling rate is influenced by the thermal properties of the coating as well as the geometry of the protrusions on the solid surface. The presence of capillary-porous coating significantly affects the dynamics of quenching, which results in the decrease more then threefold of the total quench time. In this way, the structured capillary-porous coating is a method for reducing the time and the total mass of cryogenic fluid required for a quenching process. The effect is due to the fact that the initialization of a quench front on a specimen with the coating occurs at a temperature significantly higher than the thermodynamic limit of a liquid superheat, when a stable solid-liquid contact is thermodynamically impossible. This phenomenon appears as a result of local contacts of the crests of wavy liquid flow at the liquid-vapor interface with the protrusions on the modified surface. The results indicated also the minimum film boiling temperature increase on heat transfer surface coated with capillary-porous layer. This increased temperature caused earlier transition to nucleate boiling, which results in the decrease in the quenching time. The results reliability is confirmed by direct comparison with experimental data on the quench front dynamics, velocity and geometry.
The use of self-lubricating titanium nitride and silver (TiN(Ag)) nanocomposite coatings is a promising way to reduce the wear of tools employed dry machining operations for hard-to-cut materials/alloys. To achieve an optimal performance, the Ag diffusion within the matrix needs to be carefully controlled, and its mechanisms clearly understood. In this paper we use density functional theory calculations to investigate Ag-related point defects, adhesion energies and Ag diffusion energy barriers in TiN bulk, surfaces and grain boundaries. Classical molecular dynamics simulations have been performed on TiN(Ag) systems using a hybrid MEAM/Mie force field, to understand the relative importance of the different diffusion processes. Our results show that the main Ag transport mechanism in TiN(Ag) nanocomposites is the surface diffusion occurring along intergranular spaces.
Titanium nitride (TiN) is a promising plasmonic material alternative to gold and silver thanks to its refractory character, low resistivity (< 100 µΩ cm) and compatibility with microelectronic industry processes. Extensive research is currently focusing on the development of magnetron sputtering as a large-scale technique to produce TiN thin films with low resistivity and optimized plasmonic performance. As such, more knowledge on the correlation between process parameters and the functional properties of TiN is needed. Here we report the effect of radiofrequency (RF) substrate biasing during the sputtering process on the structural, optical and electrical properties of TiN films. We employ spectroscopic ellipsometry as a sensible characterization method and we show that a moderate RF power, despite reducing the grain size, allows to achieve optimal plasmonic quality factors and a low resistivity (< 100 µΩ cm). This is attributed to the introduction of a slight under-stoichiometry in the material (i.e. TiN0.85), as opposite to the films synthesized without bias or under intense bombardment conditions. RF substrate biasing during magnetron sputtering appears thus as a viable tool to prepare TiN thin films at room temperature with desired plasmonic properties.
In this experimental investigation, the influence of different N2 gas flow rates on different properties (e.g. morphological, mechanical, etc.) of chemical vapor deposited (CVD) Titanium nitride (TiN) coatings has been discussed. The TiN coatings had been grown on Si (100) substrate at elevated temperature (1000℃) using Titanium dioxide (TiO2) powder. SEM images reveal a dense uniform microstructure with an irregular surface pattern. The surface roughness of the coatings was found to be increased from 12.42 to 28.56 nm with an increase in flow rate. XRD results indicate a B1 NaCl crystal structure of the film with reduced crystallite size with the increasing N2 flow rate. Through the corrosion test, it has been observed that due to the variation of N2 flow rate the corrosion resistance of the films decreases with increasing N2 flow rate. The mismatch of thermal expansion co-efficient in between Si substrate and TiN thin film reduces with higher N2 flow rate. The acoustic and optic phonon mode of TiN coatings have been shifted to higher intensities with higher N2 flow rate. The mechanical properties of the film reveal that the maximum value of hardness (H) and Young’s modulus (E) are 30.14 and 471.85 GPa respectively.
Low emission (Low-e) films are widely used in modern architectural glass. In this presentation, spectroscopic ellipsometry (SE) between 1.12-2.75 eV (wavelength range: 450-1100 nm) was used to investigate the temperature dependence of dielectric function of TiN films. A Drude-3Lorentz dispersion model was selected and the results show both the real part ε1 and the imaginary part ε2 increase with the deposition temperature increasing. The structure and performance of the obtained TiN samples were characterized by X-ray diffraction, Raman, scanning electron microscope, UV/Visible (UV/VIS) spectrophotometer and Hall measurements. Combining the measured results, it is found that with the deposition temperature increasing, the grain size of TiN film changed from 15.4 nm to 17.4 nm and the surface becomes rougher. The concentrations of titanium and nitrogen vacancies decrease with increasing deposition temperature. A combined Drude-3Lorentz model was used to analyze the dielectric and optical properties of the obtained TiN films. It is found that TiN samples exhibit typical Drude-Lorentz like behavior in the visible and near-infrared (NIR) regions. The results were verified by Hall measurements and UV/VIS measurements. With the deposition temperature increasing, the reflectivity increased in the NIR region and a peak reflectivity of about 93% can be obtained at the wavelength of 1000 nm. With the deposition increasing, the infrared emissivity decreased. The infrared emissivities of the TiN film deposited at 673K are 0.26 and 0.08 at wavelength of 2.5 μm and 25 μm, respectively, which shows TiN may be a good candidate for low-e film.
Solar-driven interfacial evaporation has attracted growing attention as an emerging and sustainable technology for wastewater purification and desalination. Tremendous research efforts have been dedicated to developing interfacial steam generators that can operate under realistic weather conditions such as changing solar intensity, water salinity, air flow and humidity, yet the effects of water waves have been largely neglected. Herein, we develop the first ever tumbler-shaped steam generator to improve the floating stability of interfacial steam generators. Apart from the good water evaporation rate of ∼1.3 kg m⁻² h⁻¹ under one sun in both freshwater and seawater, the tumbler-shaped monolithic steam generator demonstrates outstanding wave-piercing, anti-overturning and self-righting behavior with good structural durability in typical waves of open water. Gratifyingly, further integration of the tumbler-shaped steam generator with a triboelectric nanogenerator enables detection of several water wave parameters (frequency, height, velocity and wavelength) in real-time with high sensitivity. This work provides design protocols not only for developing stable interfacial steam generators for solar-driven water purification and desalination, but also for scaling-up clean water production in open water and engineering self-powered water wave detection, forecast, and blue energy harvest systems.
We have explored the features of coatings deposited by electron-beam evaporation of ceramic targets with different elemental composition in the fore-vacuum pressure range. The mass-to-charge composition of the beam-plasma formed, and the composition and characteristics of the coatings deposited by evaporation of ceramic targets of various different compositions have been investigated. The influence of target material elemental composition on the parameters of coatings deposited on a titanium substrate are assessed, including elemental composition, surface profile, microhardness, and Young's modulus.
Titanium nitride (TiN) as an alternative plasmonic ceramic material with superb properties including high hardness, outstanding corrosion resistance and excellent biocompatibility, has exhibited great potential for optical biochemical sensing applications. By sputtering about 35 nm–50 nm TiN on glass (f-TiN), the surface was found to provide sensing capability toward NaCl solution through the phenomenon of surface plasmon resonance. When the TiN film of about 27 nm–50 nm in thickness was sputtered onto a roughened glass surface (R–TiN), the sensing capability was improved. This was further improved when holes at nanoscale were created in the TiN film of about 19 nm–27 nm in thickness (NH–TiN). The roughened surface and nanohole patterns provided confinement of surface plasmons and significantly improved the sensitivity toward the local refractive index changes. In detail, the calculated refractive index resolution (RIR) of the optimal NH–TiN sensors for NaCl was found to be 9.5 × 10⁻⁸ refractive index unit (RIU), which had outperformed the f-TiN and R–TiN sensors. For biosensing, the optimized NH–TiN sensor was found to be capable to detect both small and large biomolecules, i.e. biotin (molecular weight of 244.3 g/mol) and human IgG (160,000 g/mol), in a label-free manner. Especially, the NH–TiN sensor significantly improved sensitivity in detecting small molecules due to the localized plasmonic confinement of electromagnetic field. Combining with the excellent mechanical and durability properties of TiN, the proposed NH–TiN can be a strong candidate for plasmonic biosensing applications.
Efficient and stable electron selective materials compatible with commercial production are essential to the fabrication of dopant-free silicon solar cells. In this work, we report an air-stable TiN (titanium nitride) polycrystalline film, deposited using radio frequency sputtering process, as an electron selective contact in silicon solar cells. TiN films deposited at 300 W and 1.5 mTorr exhibit a low contact resistivity of 2.0 mΩ·cm2. Furthermore, the main factors and mechanisms affecting the carrier selectivity properties are also explored. TiN layers as full area rear electron contacts in n-type silicon solar cells have been successfully implemented, even though TiN film contains some oxygen. This process yields a 17% increment in relative efficiency in comparison with reference devices (n-Si/Al contact). Hence, considering the low thermal budget, scalable technique and low contact resistivity, the TiN layers can pave the way to fabricate high efficiency selective contact silicon solar cells with a higher degree of reproducibility.
Transition metal nitrides (TMNs) are emerging as a feasible alternative to noble metal co-catalyst in photocatalytic hydrogen production. Considering the recent prospects created by multicomponent systems, it is reasonable to investigate multi-component TMNs for photocatalytic hydrogen production. Herein, in an effort in that direction, ternary chromium-titanium nitride (Cr0.5Ti0.5N) nanoparticles have been synthesized by a solid-solid phase separation method, resulting in highly efficient co-catalyst for promoting photocatalytic hydrogen production of semiconductors under visible light irradiation. Both experimental results and density functional theory (DFT) calculations demonstrate that ternary Cr0.5Ti0.5N offers a comprehensive advantage by boosting photo-induced charge carriers separation and migration; improving reaction kinetics as compared to TiN and CrN. Therefore, the optimal Cr0.5Ti0.5N-based sample exhibits the highest photocatalytic hydrogen evolution rate of 2.44 mmol g−1 h−1, which has ~120 times better kinetics than the reference pure CdS sample. In fact, this result even outperforms Pt-based nanocomposites (2.06 mmol g−1 h−1).
Copper nitride (Cu3N) thin films were deposited on Soda-lime glass substrates by reactive radio-frequency (rf) magnetron sputtering in a pure nitrogen ambience, with different bias voltages (i.e., 0, 50, 150 and 250 V) being applied to the substrate holder. The effects of DC bias voltage on the structural, morphological and optical properties of the Cu3N thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–Vis spectroscopy and photoluminescence (PL) spectroscopy. XRD spectra show the single-phase polycrystalline structure of Cu3N with (100) preferential orientation. Moreover, the grain sizes, ranging from 36 nm to 19 nm, decreases with the increase in the substrate bias voltage. The AFM images show that the films become more uniform with the increase in bias voltage. Using the Tauc plot, the optical band gaps of the films were calculated, ranging from 0.71 to 1.42 eV. Furthermore, the indirect optical band gap and the optical transmittance increase with the increase in the bias voltage. The PL spectroscopy shows a shift to the lower wavelength associated with an increase in the bias voltage.
In this study, Ni-Mo alloy films with different weight ratios were coated on mild steel (G10700) by a novel and effective co-sputtering method, and their corrosion protection was investigated in 3.5 % NaCl solution. In the sputtering process, Ni and Mo targets were mounted at DC and RF sputtering guns, respectively. By introducing the sputtering gas (argon), bimetallic films were prepared under changing the power at the RF gun and keeping the current constant at the DC gun of the magnetron sputtering system. The coatings were characterized by different methods and their corrosion resistance in 3.5 % NaCl solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The results of corrosion testing revealed that there is a relation between roughness and corrosion resistance, and all of the coatings (mono and bimetallic) have a protective effect, however, the highest performance was obtained at bimetallic coatings which the best composition was for the Mo-to-Ni weight ratio of 4.5 and 0.15 for 2 min and 1-week exposure time to the corrosive solution, respectively.
TiO 2 -Ag composite films are deposited on glass substrates by a novel grid-assisted co-sputtering method, aiming at preparing films with different silver contents. The films are characterized by energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, atomic force microscopy (AFM), ultraviolet-visible spectroscopy, and photoluminescence spectroscopy. Furthermore, the parameters of saturation roughness, fractal spectra, and permutation entropy are utilized to analyze the AFM images; the permutation entropy is employed in a 2D matrix to measure the complexity. The atomic ratios of silver to titanium range from 0.09 to 7.80, and the observed optical band gaps are in the range of 3.17 to 3.26 eV. Photoluminescence spectroscopy reveals the photoinduced-electron-trapping effect of Ag particles in the structure and surface of the films governs the emission intensities. The AFM images show the roughness of the films increases by increasing the Ag content, and it can be seen that an increase in the TiO 2 content of the films results in an increase in fluctuation per area, hence increasing the permutation entropy. Therefore, it is proposed that the Ag content of the films could be predicted by surface roughness and permutation entropy measurements; the fractality of the data allows a more precise determination of silver content.
Thin film technology is a relatively young and ever-growing field in the physical and chemical sciences, which is confluence of materials science, surface science, applied physics and applied chemistry. Thin film technology has its objectives in the provision for scientific bases for the methods and materials used in thin film electronics (integrated circuits and micro-electro-mechanical system). Additionally, it provides a sufficient data in the area of applications to permit for understanding of those aspects of the subject that might still be termed an “art”. Thin films of metals were probably first prepared in asystematic manner by Michael Faraday, using electrochemical methods. Thin films go through several distinct stages during growth, each affecting the resulting film microstructure and internal stress. Hence before proceeding to synthesis and characterization, the knowledge of formation, growth and stress generation in thin film is necessary. This paper explains the influence of process parameters on stress in silicon nitride (Si3N4) thin films with experimental results.
In this study, submicron nanocrystalline TiCrN films (141 nm, ± 8 nm) are deposited on titanium-coated steel substrates, maintained at a temperature of 300 °C. The bilayer films are prepared via an RF-DC co-sputtering system under different nitrogen flow rates (7, 10, 15, and 18 sccm). The compositional, nanostructural, mechanical, and morphological properties of the bilayer films are characterized by energy-dispersive X-ray spectroscopy (EDS), grazing incidence X-ray spectroscopy (GIXRD), backscattered scanning electron microscopy (BSE), nanoindentation and nanoscratch tests, and atomic force microscopy (AFM). The EDS results reveal that the chemical composition of the top layers is Ti1Cr1+XN with −0.06 < X < 0.21. The GIXRD patterns show that a face-centered cubic solid solution structure with a relatively strong (111) texture has been formed on a hexagonal close-packed structure (α-Ti). In addition, it can be seen the crystallite size has slightly increased in the samples with higher nitrogen content while the interplanar spacing has decreased in the samples with higher chromium content. The nanoindentation and nonoscratch tests are performed under three different indentation loads (300, 500, and 1000 µN), and the residual impressions are studied by AFM images. The results of the nanoindentation tests demonstrate that the sample with the smallest interplanar spacing, the largest crystallite size and the highest nitrogen content exhibits the highest Cube Corner hardness value. The results of the nanoscratch tests suggest that the impact of surface roughness on the friction coefficient is less dominant as the ratio of root-mean-square roughness to penetration depth decreases and that the chromium content is the factor that means the friction coefficient differences. Comparing the hardness and the friction coefficient of the samples at the load of 1000 μN, it can be said that the hardness value has improved by 25% while the friction coefficient has lowered by 14%, with the lowest value of 0.3.
Trivalent Nd, Dy, Ho, Er, Tm, Sm, Eu usually act as electron trapping centers in wide band gap compounds, whereas trivalent Ce, Tb, and Pr act as hole trapping centers. When a deep electron trap is combined with a shallow hole trap, then during the thermoluminescence glow the hole is released generating recombination luminescence at the electron trap. However in case of a shallow electron trap, the electron will be released to recombine at the hole trapping center. With the knowledge on location of the lanthanide levels within the band gap one may engineer the depth of the electron trap, the depth of the hole trap, and where the recombination will take place. This all has been tested and verified for the lanthanides in GdAlO3 in [Luo et. al J. Phys. Chem. C 120 (2016) 5916.]. In this work Cr3+ is combined with various trivalent lanthanides in GdAlO3. By combining thermoluminescence with optical spectroscopy data, a consistent interpretation of all data is obtained. Cr3+} can, other than all lanthanides, act both as a deep electron trap and as deep hole trap. From the results we will deduce the location of the Cr2+ and Cr3+ levels within the band gap and with respect to the vacuum level. Besides thermoluminescence recombination via the conduction band, evidence is found for athermal (tunneling) recombination. Results on GdAO3 are compared with results on LaAlO3. A related system but with lower lying conduction band and higher lying valence band that reduces the trap depths of the lanthanides and Cr in a predictive fashion.
Amorphous titanium nitride (TiN) thin films have been prepared on silicon (Si) and glass substrates by direct-current (DC) reactive magnetron sputtering with a supported discharge (triode). Nitrogen gas (N2) at partial pressure of 0.3 Pa, 0.4 Pa, 0.5 Pa, and 0.6 Pa was used to prepare the TiN thin films, maintaining total pressure of argon and N2 of about 0.7 Pa. The chemical, microstructural, optical, and electrical properties of the TiN thin films were systematically studied. Presence of different phases of Ti with nitrogen (N), oxygen (O2), and carbon (C) elements was revealed by x-ray photoelectron spectroscopy characterization. Increase in the nitrogen pressure from 0.3 Pa to 0.6 Pa reduced the optical bandgap of the TiN thin film from 2.9 eV to 2.7 eV. Photoluminescence study showed that TiN thin film deposited at N2 partial pressure of 0.3 Pa exhibited three shoulder peaks at 330 nm, 335 nm, and 340 nm, which disappeared when the sample was deposited with N2 partial pressure of 0.6 Pa. Increase in the nitrogen content decreased the electrical resistivity of the TiN thin film from 3200 μΩ cm to 1800 μΩ cm. Atomic force microscopy studies of the TiN thin films deposited with N2 partial pressure of 0.6 Pa showed a uniform surface pattern associated with accumulation of fine grains. The results and advantages of this method of preparing TiN thin films are also reported.
Polymer or glass films impregnated with quantum dots (QDs) have potential applications for mesoscale stress/strain sensing in the interior of materials under mechanical loading. One requirement in the development of such nanocomposite sensor materials is the establishment of calibrated relations between shifts in the emission spectrum of QD systems and the input stress/strain on the composites. Here, we use a multiscale computational framework to quantify the strain-dependent blueshift in the emission spectrum of CdTe QDs uniformly distributed in a matrix material under loading of a range of strain triaxiality. The framework, which combines the finite element method, molecular dynamics simulations and the empirical tight-binding method, captures the QD/matrix interactions, possible deformation-induced phase transformations and strain-dependent band structures of the QDs. Calculations reveal that the response of the QDs is strongly dependent on state of input strain. Under hydrostatic compression, the blueshift increases monotonically with strain. Under compression with lateral/axial strain ratios between 0.0 and 0.5, the blueshift initially increases, reaches a peak at an intermediate strain, and subsequently decreases with strain. This trend reflects a competition between increases in the energy levels associated with the conduction and valence bands of the QDs. The deformation-induced blueshift is also found to be dependent on QD orientations. The averaged blueshift over all orientations for the composite under uniaxial strain condition explains the blueshift variation trend observed in laser-driven shock compression experiments. Based on the simulation result, guidelines for developing QD composites as stress/strain sensing materials are discussed.
This chapter describes thin-film growth and deposition processes. Formation of a thin film takes place via nucleation and growth processes, which involves production of the appropriate atomic, molecular, or ionic species, transport of species to the substrate through a medium, and condensation on the substrate, either directly or via a chemical and/or electrochemical reaction, to form a solid deposit. The microstructure and topographical details of a thin film of a given material depends on the kinetics of growth, and hence on the substrate temperature, the source and energy of impurity species, the chemical nature, the topography of the substrate, and gas ambients. The physical process is composed of the Physical Vapor Deposition (PVD) processes, and the chemical processes are composed of the Chemical Vapor Deposition (CVD) process, and the chemical solvent deposition process. Resistive heating is most commonly used for the deposition of thin films. The chemical composition; crystalline structure; and optical, electrical, and mechanical properties must be considered in evaluating thin films.
Several phenomena are neglected in the original “Berg model” in order to provide a simple model of the reactive sputtering process. There exist situations, however, where this simplified treatment limits the usefulness of the model. To partly correct for this, we introduce an upgraded version of the basic model. We abandon the simplifying assumption that compound targets are sputter eroded as molecules. Instead, the molecule is split and individual atoms will be sputter ejected. Also, the effect of ionized reactive gas atoms implanted into the target will be considered. We outline how to modify the original model to include these effects. Still, the mathematical treatment is maintained simple so that the new model may serve as an easy-to-understand tutorial of the complex mechanisms of reactive sputtering.
The incorporation of oxygen impurities under ambient environment conditions during reactive sputter deposition of titanium nitride (TiN) films has been studied. TiN films, prepared by DC sputtering of a Ti metal target in 100% N2 at 1 Pa in an ultra-high vacuum (UHV) sputtering apparatus, were essentially free from oxygen. When oxygen was intentionally introduced into the vacuum chamber, an impurity level of a few atomic percent was obtained at a partial pressure of 3×10-4 Pa, but the percentage increased rapidly to 10-20 at. % when the partial pressure was 1×10-3 Pa or above. It is shown that the increase in the oxygen incorporation is not well explained by the oxygen impingement rate calculated from the partial pressure. We demonstrate that the impurity concentration is related to the ratio of the number of oxygen atoms introduced into the chamber to the number of Ti atoms sputtered from the target. This suggests that oxygen gettering by Ti atoms deposited on the chamber wall significantly reduces the oxygen pressure during deposition and that oxygen incorporation in the film is governed primarily by the total amount of sputtered metal.
Ultraviolet-visible absorption spectra of nanoscaled EuS thin films reveal a blue shift of the energy between the top-valence and bottom-conduction bands. This band-gap tuning changes smoothly with decreasing film thickness and becomes significant below the exciton Bohr diameter ∼3.5 nm indicating strong quantum confinement effects. The results are reproduced in the framework of the potential morphing method in Hartree Fock approximation. The large values of the effective mass of the holes, due to localization of the EuS f-states, limit the blue shift to about 0.35 eV. This controllable band-gap tuning of magnetic semiconductor EuS renders it useful for merging spintronics and optoelectronics.
In this study, the vanadium doped titanium nitride films were deposited by atmospheric pressure chemical vapor deposition with various vanadium chloride (VCl4) molar concentrations (0%, 2% and 15%). The films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (SEM), four-point probe and ultraviolet–visible (UV/VIS) spectrophotometer. Combining the XPS and XRD results, we found that vanadium substituted titanium in TiN lattice. The SEM results showed relatively uniform granular grains surface, and typical columnar structure cross sectional. The film thickness did not change with the doping of vanadium, keeping a constant of 316 nm. With the vanadium amount increasing, TiN films showed higher visible transmittance and higher reflectivity both in near infrared and medium-far infrared region, indicating the improvement of solar control and low-emission properties.
A series CdS/PVA nanocomposite films with different amount of Cd salt have been prepared by means of the in situ synthesis method via the reaction of Cd2+-dispersed poly vinyl-alcohol (PVA) with H2S. The as-prepared films were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV–vis) absorption, photoluminescence (PL) spectra, Fourier transform infrared spectroscope (FTIR) and thermogravimetric analysis (TGA). The XRD results indicated the formation of CdS nanoparticles with hexagonal phase in the PVA matrix. The primary FTIR spectra of CdS/PVA nanocomposite in different processing stages have been discussed. The vibrational absorption peak of CdS bond at 405 cm−1 was observed, which further testified the generation of CdS nanoparticles. The TGA results showed incorporation of CdS nanoparticles significantly altered the thermal properties of PVA matrix. The photoluminescence and UV–vis spectroscopy revealed that the CdS/PVA films showed quantum confinement effect.
Structures, optical and electrical properties of Co3O4/SiO2 nanocomposites are reported. Well crystalline Co3O4 nanoparticles embedded in an amorphous SiO2 matrix is formed, and confirmed by XRD and FTIR measurements upon calcination of gel precursors up to 800 °C. The obtained nanocomposites have high surface area ∼126–312 m2 g−1, and the Co3O4 particle size was ∼7–15 nm. The optical properties of the Co3O4/SiO2 nanocomposites indicate the presence of two energy gaps; both of them are smaller than those reported for the Co3O4 bulk phase. The first is varied from 1.32 to 1.44 eV and the second one is varied from 1.76 to 1.87 eV depending on the particles size. DC conductivity was measured in the temperatures range 300–673 K. The activation energy for DC conduction varies with particle size. The conduction mechanism was suggested to be through small polarons and variable range hopping mechanisms, at high and low temperatures respectively.
A titanium nitride (TiN)-based dye-sensitized solar cell is developed where TiN is used as a charge collector and TCO-less glass as a substrate. A nanocrystalline TiO2 film was deposited onto a TCO-less glass substrate using the radio frequency (r.f.) magnetron sputtering method and capped with a TiN film with a thickness of 66 to 167 nm, which was controlled by varying sputtering time. The crystal structure of TiN layers is analyzed using XRD, chemical bonding nature and composition (TiN0.95) were confirmed by XPS and RBS, respectively. Cross-sectional scanning electron microscopic images confirmed the columnar structure of TiN films. Electrical resistance is exponentially decayed and approaches 4.4 Ω as the TiN film thickness increases up to 167 nm. The photovoltaic property is significantly influenced by the TiN film thickness. The energy conversion efficiency increases from 3.3% to 6.8% with increasing the TiN film thickness from 66 nm to 86 nm, where an increase in fill factor from 0.33 to 0.64 is mainly responsible for the efficiency improvement. The highest efficiency of 7.4% is obtained with a 136 nm-thick TiN film and declines to 5.8% at 167 nm, resulting in a one order of magnitude retarded diffusion rate of I3−. A long-term stability test was performed for 1000 h and compared with a cell with pure Ti metal. The TiN-based cell maintains an efficiency of 84% after 1000 h, while the efficiency of the Ti-based cell is degraded by 34%, indicating that TiN is more stable than Ti in the TCO-less dye-sensitized solar cell.
In this paper, the so-called Berg's model was successfully employed in order to model the reactive sputter deposition of titanium nitride (TiN) by a triode magnetron sputtering (TMS) system. Such system consists of a grounded grid introduced between the target and the substrate. The grid acts as the anode, and the glow discharge is formed between the target and grid. The qualitative model was compared to experimental data. In addition, results from a conventional MS system were also compared to the ones from the modified TMS system. It was possible to observe that (a) the width of the hysteresis region is narrower for TMS for all modeled conditions; (b) the hysteresis width increases as a function of grid-to-target distance.
The effect of the base pressure on the incorporation of oxygen into reactively magnetron-sputtered metal-nitride films has been investigated. A UHV sputtering system with a base pressure of less than 10−6Pa was used to examine the relationship between a deliberately introduced background pressure of oxygen and a measured oxygen content in the sputter-deposited TiN films. The results showed that with an oxygen partial pressure of 10−4Pa, the deposited TiN was found to include 10–20at.% of oxygen when measured by the technique of X-ray photoelectron spectroscopy (XPS). When no oxygen was admitted into the system, no trace of oxygen could be detected in the deposited TiN films. The incorporation mechanism is discussed in terms of the coverage-dependent sticking probabilities of O2 and N2 on a Ti metal surface.
Simple model description of both the target and the substrate reactions are applied to explain experimental results on the deposition rate and coating composition as a function of the nitrogen partial pressure for ZrNx, NbNx and MoNx coatings fabricated by reactive magnetron sputtering in an ArN2 atmosphere. Calculations of the influence of oxygen as a model residual gas on the composition of the coating are compared with experimental data as a function of the oxygen pressure for TiNx. The results show that the simplified models give a consistent quantitative description with reasonable semi-empirical fitting parameters for the sputtering rates and reaction coefficients at the target and the substrate.
a b s t r a c t Optical properties of the as-deposited and annealed films of 5, 10, 15, 20-Tetraphenyl-21H, 23H-Porphyrin nickel (II), (NiTPP) were investigated using spectrophotometric measurements of both transmittance and reflectance at normal incidence of light in the wavelength range, 200e1100 nm. The obtained data of refractive index, and absorption index, were used to estimate the type of transition and both optical and fundamental gaps. The normal dispersion (l > 600 nm) of refractive index is discussed in terms of single oscillator model of Wemple-Didomenico, while the anomalous dispersion (l < 600 nm) is discussed according to multi oscillator. The dispersion parameters; oscillator energy, dispersion energy, optical dielectric constant at higher frequency, lattice dielectric constant, and the ratio of carrier concentration to the effective mass N/m* were determined. The real part of the dielectric constant, the imaginary part of the dielectric constant, the loss factor, the volume and the surface energy loss functions were estimated and discussed.
B1–NaCl-structure CrN001 layers were grown on MgO001 at 600 °C by ultrahigh vacuum reactive magnetron sputter deposition in pure N 2 discharges. X-ray diffraction analyses establish the epitaxial relationship as cube-on-cube, (001) CrN (001) MgO with 100 CrN 100 MgO , while temperature-dependent measurements show that the previously reported phase transition to the orthorhombic P nma structure is, due to epitaxial constraints, absent in our layers. The resistivity increases with decreasing temperature, from 0.028 cm at 400 K to 271 cm at 20 K, indicating semiconducting behavior with hopping conduction. Optical absorption is low (210 4 cm 1) for photon energies below 0.7 eV and increases steeply at higher energies. In situ ultraviolet photoelectron spectra indicate that the density of states vanishes at the Fermi level. The overall results provide evidence for CrN exhibiting a Mott–Hubbard type band gap. © 2002 American Institute of Physics.
A robust method is used for analyzing roughness at a wide range of lateral length scales. The method is based on two-point correlation where both the amplitude and lateral spacing of surface heights are considered when determining the roughness. Atomic force microcopy and confocal optical microscopy images were captured for a set of pigment-coated samples. The effects of sampling interval, image size and filtering on surface roughness were studied. Isotropy and periodicity of roughness were determined by analyzing the angular distribution of the correlation length (T) and the autocorrelation function (ACF). A clear dependence of root mean square (RMS) roughness (σ) on T was established for randomly distributed surfaces. By taking into account the σ–T dependence it was possible to obtain σ for various length scales for each sample and thus attaining the most relevant σ for a certain surface function, which in this study was specular reflection of light (gloss). The roughness analysis showed that a small amount of DPP coating was sufficient to completely cover and change the surface of the substrate, while kaolin coatings gave a different response.