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Single crystal preparation and properties of the AgGaGeS(4)-AgGaGe(3)Se(8) solid solution
Abstract
Phase equilibria in the AgGaGeS4–AgGaGe3Se8 system were investigated using differential-thermal analysis and phase X-ray diffraction. A continuous solid solution series was discovered in the system, and the mechanism of the formation of these solid solutions was determined. Single crystals of the solid solutions were grown by the Bridgman–Stockbarger method. The crystals are of n- or p-type conductivity and their bandgap energy varies from 2.25 to 2.80eV.
... Phase diagram of the AgGaGeS 4 -AgGaGe 3 Se 8 system belongs to Type 1 of Roozeboom classification with the formation of a continuous solid solution series for the substrate compounds [23]. The refinement of the crystal structure of the equimolar composition (AgGaGe 2 S 2 Se 4 ) possessed six crystallographic sites: one of them (16b) is occupied by about half by Ag atoms. ...
... The single crystals of AgGaGe 1.8 S 2.4 Se 3.2 , AgGaGe 2.2 S 1.6 Se 4.8 and AgGaGe 2 S 2 Se 4 were grown by Bridgman-Stokbarger method. The technique of syntheses crystal and solid solutions is described in details in [23]. ...
... Specific features of the structure for these crystals are the statistical distribution of cations (Ga, Ge) and anions (S, Se) in the local sites of the crystal lattice and the presence of stoichiometric vacancies of Ag atoms Ag (V Ag ) [23]. This is likely the main reason for the deviation from the long-range order and the approach of these crystals to disordered systems. ...
... The obtained crystals have a higher range of homogeneity, surface stability to laser irradiation, more spectral transparency range, higher birefringence, and lower melting temperature, which makes the synthesis process cheaper and leads to lower prices [4][5][6][7][8][9]. Continuous variation of energy gap and other parameters of Ag x Ga x Ge 1-x Se 2 (x = 0.333, 0.250, 0.200, 0.167) allows to extend their applications in optoelectronics [10]. Moreover, by appropriate doping one can operate by free carrier lifetimes in the studied semiconductors and polarization of the titled materials. ...
... Details of the synthesis of the titled crystals were described in our earlier publications [8,10]. The crystals of three different compositions of the quaternary phase Ag x Ga x Ge 1-x Se 2 with x = 0.250, 0.200, 0.167 were grown using modified Bridgman-Stockbarger method. ...
... According to the previous publications [8][9][10][11], the crystalline structure of Ag x Ga x Ge 1-x Se 2 (x = 0.250, 0.200, 0.167) could be presented as repeating isovalent substitution of Ge 4+ atoms simultaneously by Ag + and Ga 3+ for compound GeSe 2 . The package of (Ga, Ge)Se 4 tetrahedra and inter-atomic distances Ag-Se for Ag x Ga x Ge 1-x Se 2 (x = 0.250, 0.200, 0.167) are presented in Fig. 1. ...
Complex studies of photoconductivity, two-photon absorption (TPA) and third harmonic generation (THG) were performed for three principal representatives of chalcogenide crystals. Comparison of carrier transport kinetics and third order nonlinear optical properties was performed and the principal role of the anionic co-ordination is discussed. Specific features of photoconductivity in synthesized crystals show that the relaxation kinetics of photoconductivity can be determined by the existence of at least two types of relaxation processes: slow and quick. The control of the relaxation processes for s- and r-centres was carried out by temperature dependences of t-levels relaxation photoconductivity. The maximum THG is observed for the sample AgGaGe5Se12. The less THG exists for the sample AgGaGe3Se8 and the lowest for the AgGaGe4Se10.
... Packing of the tetrahedral formed by selenium atoms in the AgGaGe3Se8 crystals. Red tetrahedra are centered on Ga1 atoms (8a), and orange ones on Ga2 atoms (16b) [21]. ...
... The crystal structure of the AgGaGe 3 Se 8 single crystals is given in the ref [21,22]. Generally their structure may be presented as the packing of the selenium formed tetrahedral ( Fig. 1). ...
... The AgGaGe 3−x Si x Se 8 single crystals were grown via Bridgman-Stockbarger method as described in details in references [21,22]. The synthesis and crystal growth were combined in the same crucible. ...
... Packing of the tetrahedral formed by selenium atoms in the AgGaGe3Se8 crystals. Red tetrahedra are centered on Ga1 atoms (8a), and orange ones on Ga2 atoms (16b) [21]. ...
... The crystal structure of the AgGaGe 3 Se 8 single crystals is given in the ref [21,22]. Generally their structure may be presented as the packing of the selenium formed tetrahedral ( Fig. 1). ...
... The AgGaGe 3−x Si x Se 8 single crystals were grown via Bridgman-Stockbarger method as described in details in references [21,22]. The synthesis and crystal growth were combined in the same crucible. ...
Photoinduced changes of piezoelectric coefficients for novel chalcogenide AgGaGe3−xSixSe8 (x =
0.15, 0.3, 0.6, 0.9) single crystals are discovered. The measurements were performed during illumination
by cw 532 nm laser (above energy band gap) with power about 400 mW. The relaxation after switching
off of the laser beam was studied. Additional temperature dependences of piezoelectric diagonal tensor
components were recorded to separate the thermal effect with respect to pure electronic contribution to
the photoinduced piezoelectricity. In addition to the photoinduced piezoelectric effect FTIR spectra are
studied in order to explore the influence of the thermal contribution. The photoinduced changes with taking
into account of temperature contribution have achieved magnitude equal to approximately 50–60% for all
the studied samples and the changes were found to be completely reversible. The possible mechanisms
for the observed effects are discussed and additional quantum chemical DFT simulations for the principal
structural fragments were performed.
... During the growth of AgGaGeS 4 crystals, many defects may occur forming additional electronic states in the band gap, making its value varying from 2.25 till 2.80 eV. 31,32 In particular, vacancies on special crystallography sites have been established to form during annealing AgGaGeS 4 crystals and their presence affects the band gap value being within the energy range of 2.787-2.805 eV in such a case. ...
... Available experimental data reveal the band gap of about 2.84 eV for AgGaGeS 4 at room temperature. 25,31,49 Meanwhile, Davydyuk et al. 33 have shown experimental data where the band gap of the AgGaGeS 4 is from 2.84 eV to above 3 eV. Therefore, in our opinion, the TB-mBJ+U method, which features the energy band gap of 3.414 eV, looks to be the most suitable for calculating the electronic properties of the AgGaGeS 4 crystal. ...
The electronic and optical properties of an AgGaGeS4 crystal were studied by first-principles calculations, where the full-potential augmented plane-wave plus local orbital (APW+lo) method was used together with exchange-correlation pseudopotential described by PBE, PBE+U, and TB-mBJ+U approaches. To verify the correctness of the present theoretical calculations, we have measured for the AgGaGeS4 crystal the XPS valence-band spectrum and the X-ray emission bands representing the energy distribution of the electronic states with the biggest contributions in the valence-band region and compared them on a general energy scale with the theoretical results. Such a comparison indicates that, the calculations within the TB-mBJ+U approach reproduce the electron-band structure peculiarities (density of states-DOS) of the AgGaGeS4 crystal which are in fairly good agreement with the experimental data based on measurements of XPS and appropriate X-ray emission spectra. In particular, the DOS of the AgGaGeS4 crystal is characterized by the existence of well-separated peaks/features in the vicinity of −18.6 eV (Ga-d states) and around −12.5 eV and −7.5 eV, which are mainly composed by hybridized Ge(Ga)-s/p and S-p state. We gained good agreement between the experimental and theoretical data with respect to the main peculiarities of the energy distribution of the electronic S 3p, Ag 4d, Ga 4p and Ge 4p states, the main contributors to the valence band of AgGaGeS4. The bottom of the conduction band is mostly donated by unoccupied Ge-s states, with smaller contributions of unoccupied Ga-s , Ag-s and S-p states, too. The AgGaGeS4 crystal is almost transparent for visible light, but it strongly absorbs ultraviolet light where the significant polarization also occurs.
... The main disadvantage of the Ag substitution by Li in the AgGaX 2 (X ¼S, Se) compounds is reducing in several times of their NLO coefficients and increasing their melting points, which are equal to 1050 and 915°C in the case of LiGaS 2 and LiGaSe 2 , respectively [13]. Numerous studies have revealed that the above drawbacks can be partly eliminated by decreasing the Li content in the LiGaX 2 compounds as well as by Ge doping [14,15]. ...
... Therefore, Mei et al. [16] have performed recently first-principles bandstructure calculations of LiGaGe 2 Se 6 and established the existence of strong hybridization of the 4 s and 4p orbitals of Ga, Ge, and Se around the Fermi level in this compound. The calculation made in Ref. [16] suggest that the refractive index is Δn¼0.04 for λZ1 mm, and the calculated major second harmonic generation tensor elements d 15 and d 33 are found to be 18.6 and 12.8 pm/V, respectively. The above facts allow suggesting that the LiGaGe 2 Se 6 compound is a very promising material for application in IR nonlinear optics [16]. ...
X-ray photoelectron core-level and valence-band spectra are measured for pristine and Ar+ ion-bombarded surfaces of LiGaGe2Se6 single crystal grown by Bridgman-Stockbarger technique. Further, electronic structure of LiGaGe2Se6 is elucidated from both theoretical and experimental viewpoints. Density functional theory (DFT) calculations are made using the augmented plane wave + local orbitals (APW+lo) method to study total and partial densities of states in the LiGaGe2Se6 compound. The present calculations indicate that the principal contributors to the valence band are the Se 4p states: they contribute mainly at the top and in the central portion of the valence band of LiGaGe2Se6, with also their significant contributions in its lower portion. The Ge 4s and Ge 4p states are among other significant contributors to the valence band of LiGaGe2Se6, contributing mainly at the bottom and in the central portion, respectively. In addition, the calculations indicate that the bottom of the conduction band is composed mainly from the unoccupied Ge s and Se p states. The present DFT calculations are supported experimentally by comparison on a common energy scale of the X-ray emission bands representing the energy distribution of the 4p states associated with Ga, Ge and Se and the XPS valence-band spectrum of the LiGaGe2Se6 single crystal. The main optical characteristics of the LiGaGe2Se6 compound are elucidated by the first-principles calculations
... Numerous works devoted to studying semiconductor solid solution (SS) properties have shown that it is possible to control their structural, electrical, optical, and luminescent properties. Today, this has been achieved in the case of numerous binary SS systems, such as Si 1−x Ge x [2], Si 1−x Sn x [3,4], and Ge 1−x Sn x [5], in three-element SS systems, such as (ZrO 2 ) 1−x (Sc 2 O 3 ) x [6], (GaSb) 1−x (Si 2 ) x [7], (Si 2 ) 1−x (GaP) x [8], Zn x Cd 1−x Se [9,10], ZnS x Se 1−x [11], Pb 1−x Sn x Te [12], InGaN [13], AlGaN [14], and InGaAs [15], in four-element SS systems, such as (GaAs) 1−x (ZnSe) x [16] and AgGaGeS 4 -AgGaGe 3 Se 8 [17], and in five-element SS systems, such as (Sn 2 ) 1−x−y (GaAs) x (ZnSe) y [18] and (ZnSe) 1−x−y (Si 2 ) x (GaP) y [19]. ...
This paper presents the results of experimental studies of the structural characteristics of the epitaxial layers of GaAs1−x−yZnSexGey solid solutions grown from a bismuth solution-melt on GaAs substrates with (100) crystallographic orientation. The grown epitaxial film of the GaAs1−x−yZnSexGey solid solution is a single crystal with a sphalerite-like structure with the (100) orientation corresponding to the substrate orientation. It is shown that ZnSe molecules partially replace GaAs molecules in defect-capable regions of the (100) matrix crystal lattice at the high-potential sites.
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... By smoothly changing the composition of the solid solution, it is possible to control the basic electrophysical and optical parameters of the material, 5-8 such as the bandgap, spectral photosensitivity region and cell parameters. [9][10][11][12] On the other hand, to obtain a high-quality solid solution suitable for creating devices, the proximity of the cell parameters of the components is of great importance. [13][14][15][16] In this regard, a solid solution consisting of GaAs, ZnSe and Ge components is of undoubted interest since the sum of the covalent radii of the molecules of these semiconductors is very close (r Ga + r As = 2.44Å, r Zn + r Se = 2.45Å and r Ge + r Ge = 2.44Å), and their bandgap values (E g ) differ significantly (E g,GaAs = 1.43 eV, E g,ZnSe = 2.68 eV and E g,Ge = 0.67 eV). ...
In this work, the physical features of growing epitaxial layers of new solid solutions of (GaAs)1−y−z(Ge2)y(ZnSe)z from the liquid phase of the tin solution-melt on GaAs (100) substrates were investigated. The conditions required for the formation of the solid solution of molecular substitution were revealed. A possible configuration of the crystal structure of the solid solution (GaAs)1−y−z(Ge2)y(ZnSe)z is presented. In the spectral photosensitivity of the n-GaAs–p-(GaAs)1−y−z(Ge2)y(ZnSe)z structures, peaks with maxima at photon energies of 1.37 eV and 2.62 eV were found. The band diagram of the solid solution (GaAs)1−y−z(Ge2)y(ZnSe)z was presented.
... The PbGa 2 GeS 6 compound lies on the PbGa 2 S 4 -GeS 2 section at the component ratio 1:1. Formation of the AgGaGeS 4 compound (SP oF88, SG 43) corresponds to the same component ratio in the silver-bearing system AgGaS 2 -GeS 2 [57]. The AgGaGeS 4 structure looks to be very similar to that of PbGa 2 GeS 6 with respect to the location of analogous tetrahedra. ...
A common feature of chalcogenide crystals is the presence of the chalcogen-chalcogen bonds, which result in very stable anion sub-structures (blocks) containing up to eight chalcogenide ions with the electric charge -2 in units of the proton charge like systems [PS4]³⁻, [SiS4]⁴⁻, [GeS4]⁴⁻, [GeSe5]⁴⁻, [Ge2Se6]⁶⁻. The size of anion blocks, their mutual arrangement and chemical bonds between them consequently determine the optical and detection properties. By modifying the chemical composition with subsequent use of the laser irradiation, it is possible to change crystal optoelectronic properties in a wide spectral range. In the work, we discuss the influence of the structural properties on the stability, electronic, optical and nonlinear-optical efficiency for the group of quaternary chalcogenide crystals with Ag(Pb)–Ga(In)–Si(Ge)–S(Se) composition, that have already found practical applications in IR optoelectronics and non-linear optics. The presented analysis of chemical composition-structure - nonlinear optical properties relationship can be useful for the creation of effective quaternary crystals for nonlinear optics application.
... However, the chalcogenide materials have limited studies as compared to oxides [6] and many new materials were found in thechemical classes of tellurides, selenides and sulfides in recent years [7][8][9][10][11][12][13][14]. These compounds have shown good optical features in the infrared regions, while single crystals were grown for application in the IR range [15][16][17][18][19][20][21][22] (see Table 1). ...
Here in we have reported on band-structure calculations, within First principles density functional theory (DFT) based calculations are performed for the investigation of the electronic and optical properties of silver lanthnide dichalcogenides XAgSe2 (X = Eu and Er). The current calculations (DFT) possess an admirable correspondence of the total density of states with the optical properties using the generalized gradient approximation. Additionally, the spin–orbit coupling (SOC) effect and Hubbard correction parameter U (GGA + SOC + U), (GGA+U) that is useful for the strongly correlated electron system The basic optical constants are calculated within the GGA + SOC + U technique and they expose a big viewpoint of using the XAgSe2 (X = Eu and Er) compound in optoelectronic appliances.
... The crystal growth technique used in this work was the vertical Bridgman-Stockbarger method as described in our previous papers and other works [22,24,29,31,32,33]. Elementary copper (Cu), gallium (Ga) and selenium (Se) were used as starting materials. ...
... The crystal growth technique used in this work was the vertical Bridgman-Stockbarger method as described in our previous papers and other works [22,24,29,31,32,33]. Elementary copper (Cu), gallium (Ga) and selenium (Se) were used as starting materials. ...
... AgGaGe 4 Se 12 [109] , AgGaGe 3 Se 8 [110] , AgGa x In 1−x - ...
High-power tunable mid-infrared (MIR) and far-infrared (FIR) lasers in a range of 3-20 μm, especially in the atmospheric windows of 3-5 μm and 8-12 μm are essential for the applications, such as in remote sensing, minimally invasive surgery, telecommunication, national security, etc. At present, the technology of MIR and FIR laser have become a research hotspot. As the core component of all-solid-state laser frequency conversion system, nonlinear optical (NLO) crystals for coherent MIR and FIR laser are urgently needed by continuously optimizing and developing. However, compared with several outstanding near infrared, visible, and ultraviolet NLO crystals, such as β-BaB 2 O 4 , LiB 3 O 5 , LiNbO 3 , KTiOPO 4 , and KBe 2 BO 3 F 2 , the generation of currently available NLO crystals for 3-20 μm laser is still underdeveloped. Traditional NLO oxide crystals are limited to output wavelengths ≤ 4 μm due to the multi-phonon absorption. In the past decades, the chalcopyrite-type AgGaS 2 , AgGaSe 2 and ZnGeP 2 have become three main commercial crystals in the MIR region due to their high second-harmonic generation coefficients and wide IR transparency ranges. Up to now, ZnGeP 2 is still the state-of-the-art crystal for high energy and high average power output in a range of 3-8 μm. Unfortunately, there are still some intrinsic drawbacks that hinder their applications, such as in poor thermal conductivity and low laser damage threshold for AgGaS 2 , non-phase-matching at 1.06 μm pumping for AgGaSe 2 , and harmful two-photon absorption at 1.06 μm for ZnGeP 2 . In addition, ZnGeP 2 has significant multi-phonon absorption in an 8-12 μm band, which restricts its applications in long wavelength MIR. With the development of research, several novel birefringent crystals, as well as all-epitaxial processing of orientation-patterned semiconductors GaAs (OP-GaAs) and GaP (OP-GaP), have been explored together with attractive properties, such as large NLO effect, wide transparency ranges, and high resistance to laser damage. In this paper, from the angle of the compositions of NLO crystal materials, several kinds of phosphide crystals (ZnGeP 2 CdSiP 2 ) and chalcogenide crystals (CdSe, GaSe, LiInS 2 series, and BaGa 4 S 7 series) are summarized. In addition, the latest achievements of the orientation-patterned materials such as OP-GaAs and OP-GaP are also reviewed systematically. In summary, we review the above-mentioned attractive properties of these materials such as in the unique capabilities, the crystal growth, and the output power in the MIR and FIR region.
... The crystal growth technique used in this work was the vertical Bridgman-Stockbarger method as described in our previous papers and other works [22,24,29,31,32,33]. Elementary copper (Cu), gallium (Ga) and selenium (Se) were used as starting materials. ...
Single crystals of
C
u
G
a
S
e
2
are prepared by a technique based on the vertical Bridgman procedure. The crystal chemical and phase compositions were identified by using dispersive X-ray fluorescence spectrometry and X-ray diffraction data analysis, respectively. The Hall effect and the electrical conductivity were determined in terms of temperature, parallel and orthogonal to the layer surface, and the parameters proved to be strongly anisotropic. From carried out measurements, different parameters such like the carrier mobilities, the carrier concentration, the relaxation time, the diffusion coefficient, and the length of diffusion for both, majority carriers and minority carriers were estimated.
... AGGS crystallizes in a non-centrosymmetric space group Fdd2 with the lattice periods a = 12.028 Å, b = 22.918 Å, c = 6.874 Å (Z = 12) [21,22]. Three sorts of sulfur atoms in this structure occupy 16b sites, germanium and gallium atoms statistically share sites 8a and 16b. ...
One of the most promising non-linear optical materials for mid-IR region that is studied
quite actively in the recent years is AgGaGeS4 (AGGS) [1‒10]. Due to high double refraction,
huge laser damage threshold, absence of absorption peaks at the solid-state laser wavelengths, the
possibility of synchronicity matching, AGGS crystals may be used for the development of
parametric frequency converters (parametric light generators pumped by solid state lasers, upconvertors
of CO2 lasers radiation to the visible range, frequency doubling) [1]. One of the factors
that hinder the widespread use of AGGS is the low manufacturability of crystals. They are mainly
obtained by Bridgman-Stockbarger method [2‒10].
. The majority of the researchers note the importance of the preparation of the quality
initial batch for the growth that affects the crystal quality and the reproducibility of its properties.
This is due to the difficulty in achieving its homogeneous state, which in turn is caused by the
existence of broad areas of glass formation in the Ag2S–Ga2S3–GeS2 system [8] and consequently
high viscosity of the melts. Most of the researchers synthesize AgGaGeS4 in a two-zone furnace,
with lengthy annealing and then crushing obtained alloy into powder after cooling, though other
approaches were also attempted.
... The obtained compound is isostructural to the SnGa 2 GeS 6 , which can be presented as laying polyhedrons around cations or as stacking M1S 4 tetrahedra and SnS 5 distorted square pyramids [21]. The crystal structure of PbGa 2 GeS 6 may be presented as a framework of sulfur tetrahedra centered around Ga atoms (yellow) and the statistical mixture of Ga, Ge (red), as shown in Fig. 2. The order of tetrahedra location is similar to that of the AgGaGeS 4 compound [22] formed at the AgGaS 2 eGeS 2 section with the component ratio 1:1 [23]. This is the same ratio as for the titled compound in the PbGa 2 S 4 eGeS 2 system. ...
New quaternary sulfide PbGa2GeS6 crystal was synthesized from co-melting high-purity elements The studies of second harmonic generation and the third harmonic generation for new quaternary sulfide PbGa2GeS6 crystal have shown that its nonlinear optical response is higher with respect to other similar compounds. The band structure analysis performed by X-ray spectroscopy methods and first principles DFT band structure calculations indicate that the main contributions of the S 3p states are located at the top of valence band, while those of the Ga 4p states give contribution to the central and upper portions of the valence band of the PbGa2GeS6 compound. The calculations reveal that the band gap Eg = 2.445 eV is indirect and is formed between the valence Γ-point and the conduction X-point of Brillouin zone. The theoretically evaluated band gap energy is close to the experimental value, namely Eg = 2.37 eV at 300 K The present results allow recommending PbGa2GeS6 for nonlinear optical application in the near IR spectral range. At the same time, the crystal possess a good transparency in the mid-IR spectral range.
... For instance, AgGaGeS 4 has an acentric orthorhombic structure (SG Fdd2 [30]). No such composition was found in the analogous AgGaSe 2 eGeSe 2 system, instead, an isostructural intermediate phase with the homogeneity region 64e90 mol % GeSe 2 was found (melting point maximum corresponds to the composition AgGaGe 3 Se 8 ) [31,32]. The crystal structure of AgGaSiSe 4 was determined quite recently to be also orthorhombic (SG Aea2) with an uncommonly large unit cell [33]. ...
Results of photoinduced nonlinear optical investigations of novel TlInGe2S6 crystals. We have discovered TlInGe2S6 as a new type of laser induced nonlinear optical materials. Following the performed measurements we can use the titled crystals for laser operated coherent wavelength transformations. It was shown, that thin, photoinduced nanolayers formed by laser energies above the energy gap as well a near the phonon resonances possess promising nonlinear optical properties. Different types of cw lasers with the same powers of the photoinduced beams were used: SHG of the Nd:YAG laser (532 nm), fundamental Nd:YAG laser (1064 nm), and IR CO2 laser with wavelength of 9400 nm.
The crystal structure of novel quaternary thallium indium germanium sulphide TlInGe2S6determined by X-ray powder method possesses trigonal space group R3. The as-derived TlInGe2S6 crystalline alloy was probed employing the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (XES) methods. Particularly, for the TlInGe2S6alloy surface, both pristine and 3.0 keV Ar+ ion-irradiated, we have monitored the XPS valence-band and core-level spectra. These measurements indicate that the TlInGe2S6surface is rather stable with respect to Ar+ ion-irradiation, which does not induce significantly near the surface layers sub-stoichiometry. Matching on a common energy scale of the XPS valence-band spectrum and the XES S Kβ1,3 and Ge Kβ2 bands indicate that main contributions of the S 3p and Ge 4p states are located in the upper and central portions of the valence band of TlInGe2S6, respectively, with significant contributions of these states in other valence-band parts as well.
... One can see that the Te atoms occupy statistically the site positions earlier occupied by Se atoms. The coordination and inter-atomic distances for cationic atoms are presented in the Fig. 2. One can see that disorder in the system is increased with respect to the initial structure AgGaGe3Se8 and inter-atomic distances are more asymmetrical [17]. ...
Spectral features of absorption were studied for
novel AgGaGe3Se7.6Te0.4 solid-state alloys at different temperatures.
The synthesized crystals structure parameters are
obtained by the X-ray Rietveld refinement method. During
increasing temperature from 100 up to 300 K, the energy
gap of AgGaGe3Se7.6Te0.4 decreases linearly from 2.05
up to 1.94 eV at a rate 5.7×10−4 еV/К. The magnitudes
of piezoelectric coefficients are significantly changed and
demonstrate substantial anisotropy. At room temperature,
these values are equal to 5.2 pm/V (d11), 31.5 pm/V (d22)
and 35.5 pm/V (d33). It is crucial that with an increasing
temperature the piezoelectric efficiencies are increased. We
have explored temperature and laser-induced changes of
piezoelectric coefficients
... Besides that their resistance to the action of laser irradiation is twice as high, the magnitude of birefringence in tetradic compounds is larger, the transparency region increases, and the melting temperature diminishes, which is favorable for the technology aimed at fabricating the good-quality crystals. AgGaGeS 4 and AgGaGe 3 Se 8 compounds are isostructural, and they form a continuous series of solid solutions [1]. ...
Single crystals of the solid solution 50 mol.% AgGaGeS 4 + 50 mol.% AgGaGe 3Se 8 are studied. Due to a statistical distribution of Ga and Ge atoms over the relevant crystal lattice sites and the presence of vacancies at Ag sites, the solid solution exhibits properties of disordered semiconductors with the maximum density of localized energy states near the middle of the energy gap. The optical and thermal bandgap energies, as well as their temperature dependences, have been determined (E g ≈ 2.30 eV at T ≈ 300 K). AgGaGe 2Se 4 single crystals are found to be photosensitive p-type semiconductors with the Fermi level locating near the middle of the bandgap. The peculiarities in the conductivity of the samples and the spectral distribution of their photoconductivity have been examined. A consistent physical model that explains the experimental results has been suggested.
... The extent of these depends principally on the ionic radii of the substitute atoms and varies from tens of mol% (e.g. 67-100 mol% AgGaGe 3 Se 8 for the Ge-Si substitution [11], or 88-100 mol% AgGaGe 3 Se 8 for the substitution Ga-In [17]) to continuous solid solution series (the substitution S-Se [18]). Here we present results of the photoinduced piezoelectricity studies of the extent of the solid solution range for AgGaGe 3 Se 8 during the Ge-Sn substitution and the related properties of the crystals for this solid solution. ...
... Since about 15 years, middle infrared (mid-IR) nonlinear optical (NLO) materials are being developed for potential applications in laser surgery, gas sensors, free space communications, photomedicine, frequency metrology, etc. (Dmitriev et al., 1999;Waynant et al., 2001;Tittel et al., 2003;Godard, 2007;Zhou et al., 2012). A number of chalcogenide semiconductors are recognized as promising NLO materials for mid-IR applications; among them are commercially available AgGaS2 and AgGaSe2 compounds, which are used for frequency conversion in the mid-IR spectral range due to wide transparency region and appropriate optical properties (Agarwal and Tan, 2005;Wang et al., 2005;Shevchuk et al., 2011;Petrov, 2012). Nevertheless, these materials suffer from comparatively low laser damage. ...
High-quality AgGaGeS4 single crystal has been successfully grown by the two-zone Bridgman method. Positions of constituent atoms in the unit cell of the AgGaGeS4 single crystal have been determined. X-ray photoelectron core-level and valence-band spectra for pristine and Ar + ion-irradiated surfaces of the single crystal under study have been recorded. It has been established that the AgGaGeS4 single crystal surface is sensitive to Ar + ion-irradiation. In particular, bombardment of the single-crystal surfaces with energy of 3.0 keV during 5 min at an ion current density of 14 A/cm 2 has induced significant composition changes in top surface layers leading to a decrease of content of Ag atoms in the layers. Comparison on a common energy scale of the the X-ray emission S K1,3 band representing energy distribution of the S 3p-like states and the X-ray photoelectron valence-band spectrum indicates that the valence S p-like states contribute mainly at the upper portion of the valence band, with also their significant contributions in other valence band regions of the AgGaGeS4 single crystal.
... Thermal annealing is carried out in a furnace at 750 K for 250 h. Further details of which are presented in Ref. [19]. ...
The photoinduced piezoelectric effect in the single crystals of AgGaGe3Se8 was discovered under the influence of 532 nm cw laser with average power about 150 mW. The changes of the piezoelectricity were explored with respect to principal diagonal components d11, d22, and d33. To study the contributions of photostimulated thermal and piezooptical effects additional measurements of temperature dependent piezoelectricity and piezo-optical coefficients were done. Substantial changes were demonstrated and their time kinetics during photoillumination was explored. The three principal diagonal piezoelectric coefficients along the crystallographic axis were studied. The reversibility of the process after switching off of the photoinducing laser is given. The effect observed may be applied for laser operated piezotronic devices. The contribution of different mechanisms in the photostimulated piezoelectricity is explored.
... The structural and optical properties of complex NLO crystals can be tuned by doping that results in solid solution formation [9,10]. However, to have a wide solid solution range without drastic defect generation and optical quality degradation, it is desirable for the end parent crystals to be isostructural [11][12][13][14][15]. As to KABO, a search for structural analogs was implemented in the past because the isovalent element substitution seems to be possible in * Corresponding author. ...
... Single crystalline samples of AgGaGe 3 Se 8 (pure and co-doped) were grown from melt by Bridgman Stockbarger method as previously described in Ref. [11]. The grown crystals showed a rate of 2–3 mm/day at a temperature gradient range of 3–5 K/mm. ...
The possibility to operate by optical spectra near the absorption edge gap was discovered for the AgGaGe3Se8:Cu semiconducting chalcogenide crystals under influence of microsecond CO2 laser with pulse energy 60mJ operating at wavelength 10.6μm. An occurrence of substantial photoinduced optical density was observed at wavelengths in the spectral range of 610-620nm. Introducing of Cu ions leads to substantial spectral asymmetry in the observed spectra. The process achieves its maximum value after the 80-120s of CO2 laser treatment and relaxes with almost irreversible changes after the same time. The contribution of thermo heating did not exceed 5-6%. Only the irreversible changes of the sample's surface topography were observed during the CO2 laser treatment, which do not influence the treatment. So the surface states do not play a principal role and the effect is prevailingly originated from the. The observed effect may be used for control of the CO2 laser power density.
Досліджено монокристали твердих розчинів 50 мол.% AgGaGeS4 + 50 мол.% AgGaGe3Se8. Внаслідок статистичного розміщення у вузлах кристалічної ґратки атомів Ga і Ge, а також наявності вузлів не заповнених атомами Ag, тверді розчини проявляють властивості невпорядкованих напівпровідників з максимальною щільністю локалізованих енергетичних станів біля середини забороненої зони. Встановлено оптичну і термічну ширину забороненої зони та їх температурну залежність (Eg ≈ 2,30 еВ при T ≈ 300 К). Монокристали розчину AgGaGe2Se4 виявилися фоточутливиминапівпровідниками p-типу провідності з положенням рівня Фермі біля середини забороненої зони. Досліджено особливості електропровідностіі спектрального розподілу фотопровідності зразків розчину. Запропоновано несуперечливу фізичну модель, яка дозволяє пояснитиекспериментально одержані результати.
AgGaGe5Se12 is a new quaternary nonlinear optical crystal which is applied to laser frequency conversion, especially converting 1.064 µm light to mid-IR range. In this work, we have synthesized the AgGaGe5Se12 polycrystal by the two-zones temperature method. By the modified Bridgman method, we have grown high-quality AgGaGe5Se12 single crystal 30 mm in diameter and 50 mm in length. The structure refinement was carried out by the Rietveld method. Besides, the XRS results were analyzed by comparing with AgGaGeS4 and AgGaGe5S12. In addition, the non-polarized Raman spectra were recorded and the intense peaks were observed at 200 and 232 cm⁻¹. The peaks were attributed to corner-sharing (CS) and edge-sharing (ES) clusters. At last, the crystal was characterized by a high transparency in the 0.6–15 µm spectral range and the absorptions at 3.4 and 7 µm, observed in the as-grown crystal, have been eliminated after annealing. Thus, AgGaGe5Se12 is appropriate for further optical experiments and more comprehensive applications.
Single crystal quality is a key issue for optical applications. Indeed, in optical frequency conversion processes, defects in single crystals can drastically decrease the conversion yield. The study of the quality of an AgGaGeS4 single crystal is presented in this work. Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-Ray Spectroscopy (EDS) was used to perform a chemical analysis mapping of a large size single crystal cut (surface 26 x 20 mm²). Chemical inhomogeneity was found along the crystal growth axes and confirmed by optical characterization showing laser beam perturbations. Compounds volatility, lack of melt homogenization and instability of crystallization front might explain this chemical inhomogeneity. Solutions to improve the crystal growth process and enhance the crystal’s quality are finally proposed.
In present article we present results of detailed study of the possibility adapting AgGaGe3Se8 single crystal properties to desired requirements by investigate the influence of the different cationic substitution on the physical properties: optical, nonlinear optical (NLO) - Second Harmonic Generation (SHG) and temperature dependent photoconductivity. We report results obtained for modified crystals based on AgGaGe3Se8 by cationic substitution of the elements belong to first - (Ag-Cu), third (Ga-In), and fourth (Ge-Sn) groups of the periodic system. For the convincing observation the effects of various impurities and compare results with obtained for virgin AgGaGe3Se8 crystal was conducted replacing at 5 mol. % one element by another.
Recently, the exploration of infrared nonlinear optical (IR NLO) materials has mainly focused on chalcogenide compounds. However, their practical applications are often hampered by the low laser damage thresholds (LDTs). It is known that wide band gaps can significantly enhance the LDTs of materials, and the introduction of alkali and alkaline earth cations would broaden the band gap. Accordingly, in this work two new compounds KSrPS4 and CsBaAsS4 with both alkali and alkaline earth cations were synthesized successfully. Both compounds crystallize in the space group Pnma (62) of the orthorhombic system, and the structures consist of isolated PnS4 (Pn = P, As) tetrahedra with the interstices occupied by K (or Cs) and Sr (or Ba) atoms, respectively. The band gaps of compounds were determined by different methods. The UV-visible diffuse reflectance spectra revealed that the band gaps of KSrPS4 and CsBaAsS4 are larger than 3.62 eV and 2.86 eV, respectively. The band gaps are primarily determined by the PnS4 tetrahedra.
Single-phase AgGaGeS4 polycrystalline materials were synthesized directly from the constituent elements by vapor transporting and mechanical oscillation method. The problem of explosions was solved by careful control of the heating and cooling cycle and adopting the two-zone rocking furnace with specially designed temperature profile. The mechanical and temperature oscillations, as well as gradient cooling, were introduced in the synthesis process. The X-ray diffraction (XRD) analysis and Energy Dispersive Spectrometer (EDS) micro analysis indicated that the synthesized compound is a single-phase AgGaGeS4 polycrystalline material.
In this research work, Ag-containing quaternary-chalcogenide compounds KAg2TS4 (T=P, Sb) (I-II) and RbAg2SbS4 (III) have been studied by means of Density Functional Theory as potential IR nonlinear optical materials. The origin of wide band gap, different optical anisotropy and large SHG response is explained via a combination of density of states, electronic density difference and bond population analysis. It is indicated that the different covalent interaction behavior of P-S and Sb-S bonds dominates the band gap and birefringence. Specifically, the Ag-containing chalcogenide compound KAg2PS4 possesses wide band gap and SHG response comparable with that of AgGaS2. By exploring the origin of the band gap and NLO response for compounds KAg2TS4 (T=P, Sb), we found the determination factor to the properties is different, especially the roles of Ag-d orbitals and bonding behavior of P-S or Sb-S. Thus, the compounds KAg2TS4 (T=P, Sb) and RbAg2SbS4 can be used in infrared (IR) region.
Ag1-xGa1-xSixSe2 solutions with high Si doping level (x =1/2) are considered and new compound AgGaSiSe4 has been synthesized. It crystallizes in space group Aea2 and possesses very long axis of a =63.06(1)Å. The three-dimensional framework in AgGaSiSe4 is composed of AgSe3 trigonal planar units, AgSe4 tetrahedra and MSe4(M=Si, Ga) tetrahedra. AgGaSiSe4 is a congruently melting compound with the melt temperature of 759℃. The diffuse reflectance measurements reveal the band gap of 2.63 eV in AgGaSiSe4 and the value is 0.33 eV larger than that of Ag3Ga3SiSe8 (2.30 eV).
Optical quality GaSe crystals with diameter of 10 mm have been grown by modified Bridgman method using unusual oscillating temperature regime in the middle zone at the level of crystallization front. Cleaved surface (001) has been evaluated by SEM and AFM. Basic cleaved surface with area up to ~200 mm2 is flat with as low rms parameter as 0,3 nm. Such local defects as hillocks up to 35 nm and mesostructure are observed by SEM and AFM.
The GaSe crystal doped with AgGaS2 has been grown and evaluated by SEM and TEM. The chemical composition analysis has been produced by atomic spectrometry methods. Micromorphology and structural parameters of GaSe:AgGaS2 crystal are very similar to those of pure GaSe. The inhomogeneous distribution of Ag over crystal probes has been detected by atomic-absorption spectrometry (AAS). Generally, the GaSe:AgGaS2 crystal has been classified as a GaSe:S solid solution with Ag precipitation.
The centimeter-sized GaSe crystals doped with 0.01, 0.05, 0.1, 0.2, 0.5,
1, 2 at.% of Al and 0.025, 0.1, 0.5, 1,2 at. % of Er have been grown by
the modified Bridgman method with heat field rotation. The crystals have
been studied in comparison with GaSe crystals doped with 0.1, 0.5, 1, 2,
3, 5, 7, 10.2 wt.% of S, 0.01, 0.1, 0.5, 1, 2, 3, 5 wt.% of In and 0.01,
0.1, 0.5, 1, 2 wt. % of Te grown by the conventional Bridgman method.
The distribution coefficient of Al in the grown GaSe:Al (≥0.1 at.%)
crystals has been estimated to be ˜8ṡ10-3 and it
is within the range of 10-2-10-3 in Er-doped
crystals. For the first time, the optimal doping levels have been
estimated for Al and Er in GaSe as 0.01- 0.05 at.% for Al and ~ 0.5 wt.%
for Er, respectively.
Abstract The basic sphalerite framework has been revealed in complex sulfide minerals: galkhaite, stalderite, aktashite and other sulfide compounds. It has been shown that the noncentrosymmetric sphalerite framework is very stringent and robust in reference to the cation type, cluster formations and the presence of vacancy. The atomic net algorithm has been applied to the comparative structure analysis. Graphical Abstract The basic sphalerite framework has been revealed in complex sulfide crystals.
Quaternary single crystals AgxGaxGe1−xSe2 (x = 0.333, 0.250, 0.200, and 0.167) have been grown by the two-zone Bridgman method. X-ray diffraction analysis has revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2. Position of constituent atoms in the unit cells of the AgxGaxGe1−xSe2 single crystals have been determined. X-ray photoelectron core-level and valence-band spectra for pristine and Ar+ ion-irradiated surfaces of the single crystals under consideration have been measured. It has been established that the AgxGaxGe1−xSe2 single crystals are very sensitive to Ar+ ion-irradiation. In particular, bombardment of the single-crystal surfaces with energy of 3.0 keV during 5 min at an ion current density of 14 μA/cm2 has induced significant modification in top surface layers leading to complete elimination of Ag atoms in the layers. Furthermore, for all four AgxGaxGe1−xSe2 single crystals, the charge states of Ag, Ga, and Ge atoms do not alter when varying the x value, whilst the negative charge of selenium atoms slightly decreases with decreasing x value. All the crystals show substantial photo induced changes of absorption under influence of 808 nm 0.8 W cw laser.
The phase identification of AgGaGeS4·nGeS2 (n=0–4) crystals grown by vertical Bridgman–Stockbarger technique was carried out to find the boundary value n between a homogeneous solid solution and its mixture with GeS2. To obtain reliable results, the conventional methods of X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) were completed by less common vapor pressure measurement in a closed volume and precise density measurements, which are very sensitive to the detection of small amounts of crystalline and glassy GeS2 and heterogeneous state of the crystals. The boundary value n=1.5 at 1045 K and the coexistence of the solid solution AgGaGeS4·1.5GeS2 with the β-GeS2 phase for n>1.5 was found. Glassy GeS2 (~2 mol%) was revealed by vapor pressure measurement and XRD studies in all the crystals. This is discussed in terms of the supersaturated solid solution decomposition upon temperature decreasing and the microphase separation of overcooled melt near the melting point under non-equilibrium crystallization. For the first time, the p–T dependence for glassy GeS2 was measured by the vapor pressure measurements.
Available information on polymorph modifications observed for AgLnX2 (Ln = Dy, Ho, Er; X = S, Se, Te) compounds has been analyzed comparatively. Cubic poly-morph with mixed (0.5Ag + 0.5Ln) cation positions is generally formed at high temperatures. Formation of monoclinic, orthorhombic and tetragonal acentric crystals is found at low temperature depending on the anion type.
The new compound LiGaGe(2)Se(6) has been synthesized. It crystallizes in the orthorhombic space group Fdd2 with a = 12.501(3) Å, b = 23.683(5) Å, c = 7.1196(14) Å, and Z = 8. The structure is a three-dimensional framework composed of corner-sharing LiSe(4), GaSe(4), and GeSe(4) tetrahedra. The compound exhibits a powder second harmonic generation signal at 2 μm that is about half that of the benchmark material AgGaSe(2) and possesses a wide band gap of about 2.64(2) eV. LiGaGe(2)Se(6) melts congruently at a rather low temperature of 710 °C, which indicates that bulk crystals can be obtained by the Bridgman-Stockbarger technique. According to a first-principles calculation, there is strong hybridization of the 4s and 4p orbitals of Ga, Ge, and Se around the Fermi level. The calculated birefractive index is Δn = 0.04 for λ ≥ 1 μm, and the calculated major SHG tensor elements are d(15) = 18.6 pm/V and d(33) = 12.8 pm/V. This new material is promising for application in IR nonlinear optics.
A theoretical model was presented to deal with optical frequency conversion in mixed nonlinear crystals with a small random variation of the composition ratio. For the pump of collimated Gaussian beams, the output powers of sum and difference frequency generations were deduced upon the assumption that the randomness is subject to the stationary Gaussian stochastic process. The induced efficiency reduction relies on the variance and correlation scales of a given varying composition ratio, which widens the phase matching bandwidth as well. The result was generalized to combined mixed crystals involving the gradual index variation. Acceptable composition ratios in different cases were also developed, as they could be applied more easily in practice. The study also includes an analysis of an intentional sinusoidal compositional modulation, which provokes potential applications in the frequency conversions of multiband lasers. The model was also exemplified by applying it to Ag Ga 1 − x In x Se 2 .
A theoretical model is presented to deal with optical frequency conversion in a mixed nonlinear crystal with a small linear variation in composition ratio. Using the quasi-geometrical optics method, what we believe to be new diffraction-free coupling equations are developed to describe sum and difference frequency generations. With these new frequencies, we find that an optimal crystal length exists like that in the plane-wave model. Furthermore, the optimization of generated powers with absorption, transverse index modulation, and walk-off effect are studied in detail. According to different efficiency reductions, the tolerance and acceptance of composition ratios along and vertical to the beam propagating direction are presented. Intended gradual index crystals are also discussed for their possible applications in the frequency conversion of wideband lasers and in generating pulse compressed second harmonic ultrashort pulses.
The results of radiation resistance measurements for twelve nonlinear crystals are presented. The crystals include the well-known nonlinear CdGeAs2, ZnGeP2, AgGaSe2, GaSe, AgGaS2, and Ag3AsS3 crystals operating in the middle IR range, new mixed AgGaGeS4 and Cd0.35Hg0.65Ga2S4 crystals, two-phase (orange and yellow) HgGa2S4 crystal, and the doped GaSe:In crystal. The mixed crystals and the two-phase HgGa2S4 crystal are transparent in the range from 0.4 — 0.5 to 11.5 — 14.5 μm. The measurements were performed using a pulsed single-mode highly stability TEA CO2 laser with an output pulse duration of ~30 ns. The damage thresholds of new nonlinear AgGaGeS4 and Cd 0.35Hg0.65Ga2S4 crystals and of the HgGa2S4 crystal (the orange and yellow phases) were found to be 1.5 — 2.2 times higher than for the crystals operating in the middle IR range.
Although Rietveld's method of full profile structure refinement of powder data is a much-used tool today, ab initio structure solution from powder data is still not a routine task. One of the reasons for this is that fully overlapped peaks usually cannot be handled by routine structure determination programs. This shortcoming is not present in the Crystal Structure Detn. (CSD) package which accepts intensities from powder diagrams as well as single crystal data. To demonstrate the possibilities of the CSD package, powder diagrams of 5 substances with already known crystal structure were collected and evaluated with the CSD package. The samples were scheelite (CaWO4), pentaerythritol (C(CH2OH)4), Na sulfite (Na2SO3), Cu sulfate pentahydrate (CuSO4·5H2O) and Ag Ge phosphide (Ag6Ge10P12) and showed problems typical for powder work like preferred orientation and heavy peak overlapping. For 4 of the samples, correct atomic positions for some atoms could be found from the automatic MULTAN solution, which were then used in subsequent least squares- and difference Fourier calcns. to locate the remaining atoms. Surprisingly, the cubic Ag6Ge10P12 posed the most problems for the structure solution although 1/3 of the observed intensities was single-indexed and the final R-value was >4%.
Modeling and experimental study on phase matching of second harmonic generation in different color Hg Ga 2 S 4 crystals are carried out. Using the known Sellmeier equations, the dispersion relation with weighting proportionally to short-wavelength boundary of the crystal transparency band is proposed. Optimal dispersion relations and phase-matched conditions for different color Hg Ga 2 S 4 crystals can be specified.
Nanosecond AgGaS2 type-I singly resonant optical parametric oscillator pumped by a Q-switched 1.064 µm Nd:YAG laser is demonstrated experimentally. Continuously tunable 2.6–5.3 µm radiation and output pulse energy up to 0.6 mJ at 4 µm are achieved in a single-stage conversion process. The analysis of pump threshold is investigated both theoretically and experimentally.
Measurement of the key thermo-optic properties of AgGaSe2 in the temperature range below 300 K is reported. Values of these properties on cooling become favorable for the higher average-power operation of nonlinear optical frequency converters using this material.
The AgGaS2-GeS2 section has been investigated using the methods of physico-chemical analyses. The existence of α-tetragonal, β-monoclinic solid solutions on the basis of the initial compounds and the intermediate γ-phase, which crystallizes in Fdd2 space group, has been established. The γ-phase forms the eutectics with the initial components. Their coordinates are: 42 mol.% GeS2 (1121 K) and 93 mol.% GeS2 (1095 K).
Isothermal sections of quasi-ternary systems Ag2S–In2S3–Si(Ge)S2 at 298 K were constructed using XRD results. Vertical sections Ag2S–In2S3, AgInS2–SiS2, AgIn5S8–Ag1.57SiS2.79 were investigated in the Ag2S–In2S3–SiS2 system. Two new quaternary compounds were discovered in the systems, Ag2In2SiS6 (melts incongruently at 1133 K) and Ag2In2GeS6. Both compounds crystallize in the monoclinic structure (structural type Ag2In2GeSe6, space group Cc) with lattice parameters a = 1.21379(3) nm, b = 0.71681(2) nm, c = 1.21171(4) nm, β = 109.252(2)° and a = 1.22089(4) nm, b = 0.72115(3) nm, c = 1.21978(5) nm, β = 109.508(2)°, respectively. Atomic parameters were refined in the isotropic approximation to RI = 0.0746, RP = 0.1256 (Ag2In2SiS6); RI = 0.0657, RP = 0.1189 (Ag2In2GeS6).
A novel quaternary crystal system of the class Ag–Ga–Ge–Se was studied in detail. A process was developed to react 120 g and larger batches of material from the pure Ag, Ga, Ge and Se elements. Crystals 19–25 mm in diameter and several cm long with AgGaGe5Se12 and AgGaGe3Se8 stoichiometric compositions were grown by the vertical Bridgman method. Optical measurements of parallel polished crystals showed transparency from 0.60 to 16 μm. Both crystals belong to the orthorhombic class and showed very good fabricability. The heat capacity of the AgGaGe3Se8 material was 0.28 J/g °C and the thermal conductivity was 0.30 W/m K. Experimental second harmonic generation (SHG) gave a “d31” coefficient of 29 pm/V for both compositions. The optical parametric oscillation (OPO) analysis indicates that type-I phase matching is possible with the AgGaGe5Se12 crystal for conversion to the IR using 1.06 μm pump wavelength. The combination of transparency, low loss and phase matching results indicate that this material will enable 1.06 μm conversion to mid-wave IR (MWIR) and long-wave IR (LWIR) regions.
AgGaS2 has been studied using differential thermal analysis (DTA) technique. The melting point and solidification temperature of AgGaS2 were determined, indicating its large supercooling degree. A phase transformation point has been found. It was concluded by discussions with the DTA results and the phase diagram that the excess Ga2S3 came inevitably out of the AgGaS2 as precipitates of an intermediate phase (named Ag2Ga20S31). The results optimized the growth parameters and heat treatment procedures. Large, high optical quality AgGaS2 crystals have been obtained, and after heat treatment, it can be used for optical devices.
AgGaGeS4 and AgGaGe5Se12 are promising new nonlinear optical crystals for frequency-shifting 1-μm solid state lasers into the mid-infrared (2–12 μm) spectral range. The quaternary compounds were synthesized by vapor transport in sealed ampoules from high purity elemental starting materials, and crystals were grown by the horizontal gradient freeze technique in transparent furnaces. AgGaGe5Se12 exhibited incongruent melting behavior, and small optical samples extracted from an as-grown polycrystalline boule had high scattering losses. AgGaGeS4 growth was far more favorable, resulting in a crack-free single crystal measuring 19 mm in diameter and >80 mm in length with as-grown 2.05-μm absorption losses <0.05 cm−1. The measured laser damage threshold of an uncoated AgGaGeS4 crystal at 2.05 μm was 1.1 J/cm2, and room-temperature measurements of thermal diffusivity, heat capacity, and thermal conductivity yielded values of 0.224 mm2/s, 0.448 J/g/K, and 0.399 W/mK respectively, for the sulfide.
Mastering of the middle IR range is attractive for many applications, such as lidar gas analyzers, optoelectronic countermeasures for suppression of IR detecting, optical communication systems, and scientific and medical instrument. However, until now this has been held back by the lack of commercial coherent radiation sources with necessary energy parameters and efficiency. AgGa1-xInxSe2 and Hg1-xCdxGa2S4 are well-known middle IR crystal families introduced in recent years. The main advantage of them is that their physical properties including refractive indices and birefringence can be engineered by varying the contents of Ga, In, Cd and Hg. Consequently, the phase matching range can be extended and the 90° non-critical phase matching in three-wave interaction can be realized within a certain wavelength band. In consideration of influence of composition ratio, acceptable composition ratio and group velocity mismatch of ultra-short pulses on nonlinear properties of AgGa1-xInxSe2 and Hg1-xCdxGa2S4 are investigated for the first time. The corresponding phase-matching diagrams and spectral dependence of the acceptable composition ratio on wavelengths for second harmonic generation and optical parametric oscillation pumped by the popular Nd3+:YAG (1.06 mum) and Ho3+:ILF (2.08 mum) lasers are estimated and demonstrated with accounting of available Sellmeier coefficients. Group velocity matching for second harmonic, optical parametric generation under the pump of the two lasers in AgGa1-xInxSe2 and Hg1-xCdxGa2S4 are carried out as well. All relative results are compared and analyzed within a number of sampling values or continuum of composition ratios. In addition, the utilities of AgGa1-xInxSe2 and Hg1-xCdxGa2S4 for second harmonic generation are also discussed finally.
In this paper we report optical parametric amplification in single crystals of AgGaGeS4 using pump pulses at 820 nm to produce femtosecond pulses in the mid-IR tunable between 3.8 and 11 μm. This new crystal is considered to be used in high-power applications and the greater variety of phase-matching schemes due to its larger birefringence and biaxial nature.
The vaporization behavior of AgGaGeS4 crystals has been studied using vapor pressure measurements (gradient heating under dynamic vacuum, frozen equilibrium method,
and membrane measurements). AgGaGeS4 has been shown to vaporize incongruently, losing predominantly GeS2. The total saturated vapor pressure over AgGaGeS4 crystals has been measured, and has been represented by a best fit equation. The results are discussed in relation to earlier
data on the melting point and melting behavior of AgGaGeS4 crystals.
The phase equilibria in the AgGaSe2GeSe2 quasi-binary system were studied using differential thermal analysis and X-ray diffraction. It was established that the given section is quasi-binary in the Ag2SeGa2Se2GeSe2 ternary system and contains three regions of solid solutions.The crystal chemistry properties of phases of variable composition were studied. The structure of these phases depends directly on the tetrahedral cavity filling by silver ions.A method for obtaining single crystals from the region of γ-solid solutions was worked out. The orientation of the obtained single crystals was determined by X-ray diffraction.
The phase diagram of the Ag2S-Ga2S3-GeS2 pseudo-ternary system has been studied using DTA and XRD experiments. Only one quaternary compound was observed: AgGaGeS4, which presents a binary peritectic-type decomposition at 840°C. Four ternary invariants were found: two eutectics and two peritectics. The phase diagrams of the following systems are described: Ag2S-Ga2S3, AgGaS2-GaS2, Ga2S3-AgGaGeS4, AgGaGeS4-Ag8GeS6, and Ag9GaS6-Ag8GeS6. The system shows a large-sized glassy domain resulting from glasses of the GeS2-Ga2S3 and GeS2-Ag2S binary systems, which does not reach the Ga2S3-Ag2S quasi binary system. Glass transition Tg and crystallization Tc temperatures decreased as silver content increased.
High quality nonlinear infrared crystal material AgGeGaS4 with size 30mm diameter and 80mm length was grown via reaction of raw materials AgGaS2 and GeS2 directly. The as-prepared products were characterized with X-ray powder diffraction pattern and their optical properties were studied by spectroscopic transmittance. The absorption coefficient in the region of 6.8–7.8μm is as low as 0.02cm−1, also, frequency doubling for 2.79, 8μm with different lasers was demonstrated successfully. The reaction conditions are easy to be maintained and controlled, which may provide a new method to produce other high-quality AgxGaxGe1−xS2 materials via changing the amount of GeS2.
The quaternary compound AgGaGeS4 crystallizes in non-central symmetric space group and is a prospective material for optoelectronics and non-linear optics. In this paper we present the results of the growth of AgGaGeS4, the single crystals and the investigation of some of its properties.
We study the birefringence and nonlinearity of quaternary semiconductors of the type AgGaGenSe2(n+1), solid solutions in the system AgGaSe2–nGeSe2. The birefringence, e.g. na-nc at 1064.2nm, increases from 0.114 for n=2 (AgGaGe2Se6) to 0.149 for n=5 (AgGaGe5Se12) which substantially exceeds the birefringence of the uniaxial AgGaSe2 (∼0.022), the parent compound in the limit n=0. Sellmeier equations valid in the 0.6–11.5μm range are constructed for the solid solutions with n=2…5. All four quaternary compounds are optically negative biaxial crystals. The calculated second-harmonic generation (SHG) limit (minimum fundamental wavelength) is ≈1470nm for AgGaGe2Se6 and ≈1240nm for AgGaGe5Se12, for type-I interaction and propagation along the Y principal optical axis. These limits are much lower than the ≈3120nm limit for type-I interaction in AgGaSe2. Thus, the AgGaGenSe2(n+1) orthorhombic crystals can be used for SHG down to their band-edge. The results for the nonlinear coefficients of AgGaGenSe2(n+1) (n=3, 4 and 5), obtained from phase-matched SHG, indicate weak dependence on the composition. On the average, the larger nonlinear coefficient d31 is very close to d36 of AgGaSe2 (∼30pm/V) while d32 is roughly two times smaller.
We present data on the linear and nonlinear optical properties of the quaternary semiconductor AgGaGeS4 having orthorhombic symmetry––a solid solution in the system AgxGaxGe1−xS2 with x=0.5. After numerical analysis of the phase-matching configurations for three-wave nonlinear interactions, first experimental results on optical parametric amplification producing tunable (3.8–11 μm) femtosecond idler pulses are described and the results compared with the calculations. Due to its higher damage threshold and greater variety of phase-matching schemes AgGaGeS4 could become an alternative to the widely spread now AgGaS2 in high power and specific applications.
First-principles calculations of the second-order optical response coefficients are reported for Ag–III–VI2 compounds with III=Ga, In and VI=S, Se, Te. While both the substitutions of In for Ga and Te for Se or S lower the band gap by similar amounts, the substitution of Se by Te is significantly more favorable for increasing χ(2). The enhancement of χ(2) by a factor 2 from AgGaSe2 to AgGaTe2 is surprising compared to the only modest enhancement obtained in II–VI compounds. The origin of these enhancements is analyzed in terms of the frequency-dependent response functions and the band structures. © 2000 American Institute of Physics.
We report the results of directional solidification of three samples whose compositions belong to the Ag2S-Ga2S3 system. This system was reported to be a quasi-binary join of the Ag-Ga-S ternary system. By our data, the trajectories of melt and solid compositions do not lie in the plane of this join. It follows from this that the Ag2S-Ga2S3 join is not quasi-binary.
A diagram showing the relationships between point symmetry and a set of physical properties has been created for centrosymmetric (CS) and noncentrosymmetric (NCS) crystals. The “acentric” (ferro-, pyro- and piezoelectrical, electrooptical, nonlinear optical, ferromagnetic, enantiomorphic, girotropic), ferroelastic, ferromagnetic and refractive characteristics are accounted. The distribution of crystals over symmetry classes are plotted for CS and NCS elements and their oxides. This diagram is helpful for classification and searching new materials.
IR transparent bulk-crystallized chalcogenide glasses purely containing nontoxic and excellent nonlinear optical crystallites AgGaGeS4 were fabricated through careful ceramization process of the as-prepared glasses with the composition 53GeS2�47AgGaGeS4 at a temperature of 350 �C for various durations. The second-order optical nonlinearity of bulk-crystallized chalcogenide glasses was discussed on the
basis of Maker fringe theory. A large second-order optical nonlinearity (for k = 1064 nm) up to 5.79 pm/V, was evaluated in the IR transparent chalcogenide glass bulk-crystallized for 24 h.
In this work we consider experiments with directed crystallization of melts with slight deviation from stoichiometric composition of AgGaS2. The evolution of melt composition was calculated for both experiments using measured chemical composition of the solid phase. Also the difference in unit cell parameters and luminescence spectra for AgGaS2 grown from the melts was found. Both monocrystal samples and samples synthesized from elementary Ag, Ga and S were used for thermal analyses. Obtained data suggests that different ways of preparing the samples are responsible for defects concentration and thus for so wide range (70°C) of melting temperatures reported in scientific literature. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
The quasi-ternary CuGaS2–CuInS2–2CdS system was investigated using differential-thermal analysis and phase X-ray diffraction. Isothermal section of the system at 870 K and projection of the liquidus surface were constructed. Limits of the boundary solid solutions were determined.
Phase-matching conditions are considered for second harmonic generation (SHG) and optical parametric generation in LiGa(S1−xSex)2 mixed crystals as a function of chemical composition under the supposition of linear dependence of refractive indices on x. It has been shown that by tuning x over the range 0–1 the SHG can be realized in XY plane for pumping at ϕ=43–90°, in YZ plane for λ=2.1–2.2 and 4.8–7.8 μm pumping at θ=0–90°, and in XZ plane for pumping at θ=0–57°. The LiGa(S1−xSex)2 solid solutions are also attractive for design of tunable femtosecond pulse frequency converters with saving of pump pulse duration.
The sets of 412 noncentrosymmetric (NCS) binary and >130 ternary sulfides and 160 binary selenides have been compilled and classified. The elliptical regions on the plane of the shortest chemical bond lengths between cations and sulphur have been defined. The NCS crystals are located only into these regions. Relationship between nonlinear optical susceptibility χ(2) and chemical bonding in sulfides has been considered. The intervals of the shortest cation–anion bond lengths promising for high rank χ(2) have been estimated for the compounds.
et Je ´rˆ ome Dugue ´, Syst? eme pseudo-ternaire Ag2S–Ga2S3–GeS2: diagramme de phases-Domaine vitreux
- Noura Chbani
- Anne-Marie
- Loireau
- Lozac
- Jacques
Noura Chbani, Anne-Marie Loireau-Lozac’h, Jacques Rivet, et Je ´rˆ ome Dugue ´, Syst? eme pseudo-ternaire Ag2S–Ga2S3–GeS2: diagramme de phases-Domaine vitreux, J. Solid State Chem. 117 (1995) 189–200.
Dependence of E g on crystal composition in the AgGaGeS 4 –AgGaGe 3 Se 8 system
- M V Fig
- Shevchuk
Fig. 6. Dependence of E g on crystal composition in the AgGaGeS 4 –AgGaGe 3 Se 8 system. M.V. Shevchuk et al. / Journal of Crystal Growth 318 (2011) 708–712
- Tie-Jun Wang
- Zhi-Hui Kang
- Hong-Zhi Zhang
- Zhi-Shu Feng
- Feng-Guang Wu
- Hai-Yan Zang
- Yun Jiang
Tie-Jun Wang, Zhi-Hui Kang, Hong-Zhi Zhang, Zhi-Shu Feng, Feng-Guang Wu,
Hai-Yan Zang, Yun Jiang, Jin-Yue Gao, Yury Andreev, Grigory Lanskii,
Victor Atuchin, Oleg Parasyuk, Sellmeier equations for green, yellow, and
orange colored HgGa 2 S 4 crystals, Appl. Phys. Lett. 90 (2007) 181913.