Sphalerite-type Structure Research Articles

Sputter Deposition of Fe-Co Nitride for Ferromagnetic Granular Nitride Thin Film

Sputter deposited Fe0.7Co0.3 nitride thin film had zinc blende structure. It was thermally decomposed completely back to the ferromagnetic Fe0.7Co0.3 alloy above 400°C. As-deposited nitride thin films obtained in cosputtering of (Fe0.7Co0.3)1-xAlx composite target with nitrogen sputter gas were solid solutions with zinc blende (x≤0.44) and wurtzite (x>0.5) type structure, respectively. The largest magneto resistance ratio of 0.24% was observed on the Fe0.7Co0.3 alloy particles dispersed in AlN thin film obtained by thermal decomposition of the nitride solid solution with x=0.66 at 500°C.

Characteristic features of crystal chemistry of natural mercury-containing sulfides and sulfosalts

Many mercury-containing minerals belonging to the class of sulfides and sulfosalts are based on a highly symmetric sphalerite type structure (ZnS), where both components occupy sites with high point symmetry providing stable orientation of directed interatomic interactions. Some structures of natural compounds of this type are used to demonstrate that the geometric matrix of cations and anions tends to be preserved during variation of the chemical composition caused by migration of elements under natural conditions. The fundamental laws of crystal formation are confirmed: the governing role of the families of close packed (crystallographic) planes, the independence of ordering of different types of atoms, the tendency of sulfur atoms to mirror plane symmetry, and the trend to cluster formation in the development of crystal structures, as exemplified by [As4S12]12−, [(Cs,Tl)S12]23−, [Tl2S12]22− atomic groups.

In‐situ investigation of the structural phase transition in kesterite

AbstractA polycrystalline Cu2ZnSnS4 sample (kesterite) was investigated by in‐situ high temperature diffraction using synchrotron X‐rays, revealing for the first time a structural phase transition from the tetragonal kesterite type structure (space group I$ \bar 4 $2m) to the cubic sphalerite type structure (space group F$ \bar 4 $3m). Within 866–883 °C a phase transition region occurs, were a tetragonal phase and a cubic phase coexists. Outside the phase transition region, the lattice parameter of the tetragonal phase increase nearly linearly with increasing temperature, whereas the lattice parameter of the cubic phase show first a negative thermal expansion changing at ∼930 °C to a further linear increase of acub. A cation anti‐site occupancy can only be observed within the phase transition region. On the other hand, the anion position parameters x and z change, which starts at ∼150 °C and lasts up to the phase transition region. Both atomic position parameters reach nearly the ideal value of 1/4, indicating the anion in the middle of the cation tetrahedra. Thus the structural phase transition in Cu2ZnSnS4 from the tetragonal kesterite type to the cubic sphalerite type structure is characterized much more by a displacive behaviour of the anion substructure then by an anti‐site occupancy of the cation substructure. Because the space group I$ \bar 4 $2m) is not a subgroup of I$ \bar 4 $2d) and a group‐subgroup relation is mandatory for displacive phase transitions, the non‐existence of a I$ \bar 4 $2m) → I$ \bar 4 $2d) transition seems plausible. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ab initio study on the electronic and mechanical properties of ReB and ReC

The structural, electronic, and mechanical properties of ReB and ReC have been studied by use of the density functional theory. For each compound, six structures are considered, i.e., hexagonal WC, NiAs, wurtzite, cubic NaCl, CsCl, and zinc-blende type structures. The results indicate that for ReB and ReC, WC type structure is energetically the most stable among the considered structures, followed by NiAs type structure. ReB–WC (i.e., ReB in WC type structure) and ReB–NiAs are both thermodynamically and mechanically stable. ReC–WC and ReC–NiAs are mechanically stable and becomes thermodynamically stable above 35 and 55 GPa, respectively. The estimated hardness from shear modulus is 34 GPa for ReB–WC, 28 GPa for ReB–NiAs, 35 GPa for ReC–WC and 37 GPa for ReC–NiAs, indicating that they are potential candidates to be ultra-incompressible and hard materials.

Mn deposition on GaAs(0 0 1)-c(4×4)α reconstructed surfaces: A scanning-tunneling-microscopy study

We have investigated the initial growth of Mn on GaAs(0 0 1)-c(4×4)α reconstructed surfaces at a substrate temperature of 320 °C using scanning-tunneling-microscopy. Up to the nominal deposition of 2 atomic layers of Mn, Mn grows on GaAs(0 0 1)-c(4×4)α reconstructed surfaces by the mechanism of double-layer formation and maintains a zincblende-type structure.

Optimum growth of ZnSe film by molecular beam deposition

Zinc selenide (ZnSe) thin film has been grown originally on Coning 7059 glass substrate by molecular beam deposition (MBD). Optimum growth condition has been determined rapidly by comparing and analyzing the relative characteristics of X-ray diffraction spectrum. In this paper, films deposited at different substrate temperatures as a function of Zn/Se beam equivalent pressure (BEP) ratios are investigated. As-grown ZnSe films are polycrystalline and have a cubic (zinc-blende type) structure by the X-ray diffraction technique. The composition of ZnSe film was determined by Energy dispersive spectroscopic (EDS) analysis. Optical properties of ZnSe film were characterized by photoluminescence spectra. Structural parameters such as lattice constant, grain size, strain, dislocation density calculated are correlated with various growth conditions. The dependence of film properties on various substrate temperatures and Se/Zn BEP ratios has been discussed in detail. Finally, high quality of ZnSe film has been successfully obtained and ready for device application.

First principle calculations of the ground state properties and structural phase transformation for ternary chalcogenide semiconductor under high pressure

We report the electronic structure calculations on ZnMgO 2, ZnCdO 2, CdMgO 2, ZnMgS 2, ZnCdS 2 and CdMgS 2 in the chalcopyrite, rock salt, wurtzite and zincblende structures. From this study we conclude that II–VI semiconductor ternary alloys are direct band semiconductors and from the energy considerations we arrive at the conclusion that these ternary compounds are found to be more stable in chalcopyrite type structure rather than in rock salt, wurtzite or zincblende type structures. The calculated bandgap values, cohesive energy, volume collapse, and disorder parameter (bandgap bowing) for these chalcogenides are obtained and found to be in agreement with the reported value. We predict that these alloys undergo a structural phase transition under pressure from chalcopyrite to rock salt type structure.

Correlation between ionic charge and ground-state properties in rocksalt and zinc blendestructured solids

In this paper we have evaluated the ground-state properties (i.e., bulkmodulus and cohesive energy) of rocksalt and zinc blende structuredsolids. We have presented two expressions relating the bulk modulusB (GPa) for the alkali halides, alkaline-earth chalcogenides, transition metal nitrides, rare-earth {divalent(R2+X) andtrivalent (R3+X) } monochalcogenides, group IV, III–V and II–VI semiconductors and the cohesive energyEcoh (kcal mol−1) for the alkali halides and alkaline-earth chalcogenides with the product of ionic charges(Z1Z2) and nearest-neighbourdistance d (Å). The bulk moduli and cohesive energy of rocksalt and zinc blende type structure compoundsexhibit a linear relationship when plotted on a log–log scale against the nearest-neighbour distanced (Å), but fall on different straight lines according to the ionic charge product of thecompounds. We have applied the modified relation on rocksalt and zinc blende structuredsolids and found a better agreement with experimental data as compared to thevalues evaluated by earlier researchers. The results for bulk modulus differ fromexperimental values by the following amounts: BaO—0%, LiCl—0%, LaS—0%,SmSe—0%, ZnS—0%, CdS—0%, GaP—0%, InP—0%, MgO—0.61%, CaO—0.89%,SmS—1.7%, YbSe—1.6%, UP—1.9%, EuSe—1.9%; and the results for cohesiveenergy differ from experimental values by the following amounts: LiCl—0.49%,KF—0.51%, RbF—0.54%, SrO—1.2%, NaCl—1.6%, NaF—1.8%, MgSe—1.9%.

Crystal chemistry and spectroscopic properties of ScAuSn, YAuSn, and LuAuSn

The stannides ScAuSn, YAuSn, and LuAuSn were synthesized as single phase materials from the elements via arc-melting. All samples were characterized by X-ray diffraction on powders and single crystals: MgAgAs type, F 4 ¯ 3 m , a = 641.94 ( 12 ) pm , w R 2 = 0.035 , 85 F 2 values, 5 variables for ScAuSn, a = 656.52 ( 8 ) pm , w R 2 = 0.029 , 89 F 2 values, 5 variables for LuAuSn, and NdPtSb type, P 6 3 m c , a = 463.55 ( 16 ) , c = 737.26 ( 15 ) pm , w R 2 = 0.057 , 233 F 2 values, 11 variables for YAuSn. The gold and tin atoms in ScAuSn and LuAuSn build up three-dimensional [AuSn] networks of corner-sharing AuSn 4/4 tetrahedra (278 and 284 pm Au Sn in ScAuSn and LuAuSn, respectively) similar to the blende type structure. The scandium atoms fill octahedral voids formed by the tin substructure. In contrast, the [AuSn] network of YAuSn is two-dimensional. The gold and tin atoms build up layers of puckered [Au 3Sn 3] hexagons with intralayer Au Sn distances of 277 pm, while the interlayer Au Sn distances of 297 pm are much longer. In every other layer the [Au 3Sn 3] hexagons are rotated by 60°. The layers are separated by the yttrium atoms. Spectroscopic measurements indicate significant differences in the chemical bonding properties: As revealed by both 119Sn Mössbauer spectroscopy and 119Sn solid-state NMR data, the local electronic environment at the tin site is more anisotropic in YAuSn as compared to the other materials, which feature tin on a site with cubic point symmetry. In ScAuSn, the cubic site symmetry of the scandium position is reflected by a single sharp line in the 45Sc solid-state NMR spectrum.

First-principles calculations of ground-state and high-pressure phase of magnesium telluride

Abstract We study the ground-state properties of MgTe and the behavior under pressure using the new full potential augmented plane wave plus local orbital method (FP-LAPW + lo) within the local spin density approximation (LSDA) to density functional theory. The calculations were performed in the rocksalt (B1), cesium chloride (B2), zincblende (B3), wurtzite (B4) and nickel arsenide (B81) type structures. Our calculations clearly indicate that there is a structural transition from the B8 to B2, confirming recent experimental suggestions and also show that the ground-state phase of MgTe is the nickel arsenide (B81) structure.

Investigation of the solid solution series 2(MnX)–CuInX 2 (X=S, Se)

(2MnX) x (CuInX 2) 1− x with X=S and Se were prepared by solid state reaction from the end members α-MnS, β-MnS and CuInS 2 in the range 0< x≤0.2 (≤0.6 for β-MnS) as well as MnSe and CuInSe 2 in the range 0< x≤0.1. Mixed crystals with 0≤ x≤0.1 crystallize in the tetragonal chalcopyrite type structure, (2α-MnS) x (CuInS 2) 1− x samples with 0.1< x≤0.2 and (2β-MnS) x (CuInS 2) 1− x samples up to x=0.6 consist of two phases, occuring as tetragonal domains ( x∼0.1 for X=S) within a cubic matrix with zinc-blende type structure ( x∼0.4 for X=S), indicating a miscibility gap. For tetragonal single phase samples the band gap energy, the lattice constants and the anion parameter have been determined. The first and the latter ones show a different composition dependent behaviour caused by the modification of the MnS (α-MnS with NaCl type structure, β-MnS with zinc-blende type structure) used during the synthesis. Additionally a CuMn x In 1− x S 2 powder sample, in which Mn substitutes the M III site, was investigated. The SQUID measurements revealed a well-distinct magnetic transition between 15 and 16 K as well as ferromagnetic-like hysteresis loops pronounced for temperatures below the transition temperature. Below this temperature a clear splitting between the zero field cooling (ZFC) and the field cooling (FC) curves indicate to the existence of a long-range magnetic ordering phenomenon. This behaviour was not found in the other samples were Mn substitutes both sites M I as well as M III.

Cu2MnMIVS4 (MIV = Si, Ge, Sn) — analysis of crystal structures and tetrahedra volumes of normal tetrahedral compounds

Abstract The crystal structures of the normal tetrahedral compounds Cu2MnSiS4, Cu2MnGeS4, and Cu2MnSnS4 are presented. The structures were refined from single crystal X-ray data. Cu2MnSiS4 and Cu2MnGeS4 crystallize in the space group Pmn21 in a wurtzite type superstructure. The refinement of Cu2MnSiS4 converged to R = 0.0214 and wR2 = 0.0477. The redetermination of Cu2MnGeS4 converged to R = 0.0281, wR2 = 0.0739. The tetrahedra volumes of the coordination polyhedra of the cations in these compounds are calculated and compared with those of Cu2MnSnS4 (redetermination, spacegroup I-42m, sphalerite type superstructure, R = 0.0146, wR2 = 0.0425). In the wurtzite type structures the tetrahedra volumes differ significantly for different cations while they differ only in a small range in the sphalerite type structure.

Crystal structure and cation distribution in the solid solution series 2(ZnX)–CuInX 2 (X=S, Se, Te)

The solid solution series (2ZnX) x (CuInX 2) 1− x (X=S, Se, Te) were studied by the combination of laboratory and synchrotron X-ray and by neutron powder diffraction. Within the homologous series the tetragonal distortion ¼-u increases in the sequence S→Se→Te whereas the tetragonal deformation η= c/2 a decreases. Besides that, with increasing 2ZnX content in CuInX 2 the anion position parameter u increases as expected. The cation site occupancy in the chalcopyrite type phase of single phase tetragonal samples was obtained by Rietveld analysis of the neutron diffraction data. A non-statistic Zn distribution could be deduced for all three systems. The high temperature in situ diffraction experiments with synchrotron radiation on CuInX 2 powder samples revealed the Cu–In anti-site occupation as the driving force of the temperature dependent phase transition from the chalcopyrite to the zinc-blende type structure.

Sphalerite−Chalcopyrite Polymorphism in Semimetallic ZnSnSb2

We have investigated the system ZnSnSb2 in the course of our attempts to modify thermoelectric Zn−Sb frameworks. ZnSnSb2 is only accessible when employing Sn as reactive flux in the synthesis. The material shows an order−disorder transition in the temperature interval between 225 and 240 °C and decomposes peritectically at about 360 °C. The high-temperature form of ZnSnSb2 adopts the Zn/Sn disordered cubic sphalerite-type structure. Electron microscopy investigations reveal that samples quenched from 350 °C already contain domains of the low-temperature form, which has the Zn/Sn ordered tetragonal chalcopyrite structure. The c/a ratio of the tetragonal structure is, within experimental errors, identical to the ideal value 2. This gives rise to intricate microtwinning in the low-temperature chalcopyrite form of ZnSnSb2 as obtained in samples quenched from 250 °C. First principles electronic structure calculations demonstrate that the tetragonal low-temperature form of ZnSnSb2 has a narrow band gap of about 0.2 eV. This is in agreement with the semimetallic behavior of the material found from resistivity measurement. The shape of the electronic density of states for ZnSnSb2 is similar to thermoelectric binary Zn−Sb frameworks. However, the thermopower of ZnSnSb2 is rather low with room-temperature values ranging from 10 to 30 μV/K.

Structure and Phase Relations of the Zn2x(CuIn)1‐xS2 Solid Solution Series.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Structure and phase relations of the Zn 2 x(CuIn) 1− xS 2 solid solution series

Powder samples of Zn 2 x (CuIn) 1− x S 2 alloys were prepared by solid state reaction of the elements ( T = 950 °C) and annealed with cooling rates between 2 and 42 K/h in the entire composition range. Structural parameters (e.g. lattice parameter, tetragonal deformation η) were investigated by X-ray diffraction (XRD) studies, the chemical composition was determined by EDX analysis on a transmission electron microscope. The room temperature results showed that mixed crystals in the interval 0 ≤ x < 0.1 crystallize in the tetragonal chalcopyrite-type structure and in the interval 0.4 < x ≤ 1 in the cubic sphalerite-type structure. In between, i.e. for 0.1 ≤ x ≤ 0.4, a miscibility gap was found, indicated by the coexistence of two phases, resulting in crystals containing tetragonal domains in a cubic matrix. In the single-phase regions the lattice parameter follows Vegard's rule, whereas in the 2-phase field the phases try to match in the a– b-plane ( a tetr ∼ a cub), causing an increase of the tetragonal lattice parameter c and herewith a strong increase of the tetragonal deformation η. Thus the tetragonal deformation η = c/2 a in 2-phase samples is significantly larger than in tetragonal single-phase samples and even larger than in the end member CuInS 2.

Investigation of structural anomaly and metal ordering in the solid solution 2ZnS–CuInS 2 by neutron diffraction

Powder samples of Zn 2 x (CuIn) 1 −x S 2 were synthesized by solid state reaction ( T=950°C) in sealed evacuated silica tubes. Based on neutron- and X-ray diffraction data structural parameters were determined using the Rietveld method. Samples with 0.4⩽ x⩽1 crystallize in the cubic sphalerite-type structure, samples with 0.1⩾ x⩾0 crystallize in the tetragonal chalcopyrite-type structure. A miscibility gap was found in the region 0.1< x<0.4, indicated by the coexistence of two phases, occuring as tetragonal domains in a cubic matrix. The anion displacement specifying the structural anomaly of ternary A IB IIIC 2 VI chalcopyrites relative to the binary AC zinc-blende analogon was considered in dependence on the chemical composition of the mixed crystals. This work extends the ‘conservation of tetrahedral bonds’ model to quarternary mixed crystals by modifying the equations for the ternary chalcopyrite compounds to incorporate the 2Zn↔(Cu,In) substitution as well as different types of cation ordering. A non-statistic Zn distribution on the cation sites of the chalcopyrite structure accompanied by Cu–In anti site occupation was deduced from the experimental determined anion parameter and metal site occupancies from the Rietfeld refinement of the neutron-diffraction data.

Lattice vibrations and thermal properties of carbon nitride with defect ZnS structure fromfirst-principles calculations

The phonon spectrum of C3N4 with defect zincblende-type structure(δ-C3N4) was calculated by density functional theory (DFT) techniques. The results permitan assessment of important mechanical and thermodynamical properties suchas the bulk modulus, lattice specific heat, vibration energy, thermal expansioncoefficient, and thermal Grüneisen parameter. The thermal Grüneisen parameter ofδ-C3N4 is calculated to be about 1.19 at 300 K, comparable to that of diamond. Thecoefficient of linear thermal expansion of this structure is calculated to be about2.2 × 10−6 K−1 at room temperature. The thermal conductivity coefficient ofδ-C3N4 is also estimated using Slack’s theory to be as high as about216 W m−1 K−1.

NMR Spectra of59Co and14N in CoN

Nuclear magnetic resonance (NMR) measurements of 59 Co and 14 N in CoN with a zincblende type structure were carried out in the temperature range from 4.2 K to room temperature. NMR Spectra of 59 Co are obtained from Free Induction Decay (FID) signals in a static field of 6.3068 T. NMR Spectra of 14 N are obtained by spin–echo method in the same static field. The temperature variations of Knight shifts are derived from resonance peak positions at various temperatures. In this experiment, it is found that the temperature variations of Knight shifts are very small. Therefore, it is concluded that the compound CoN has Pauli paramagnetism. This is consistent with the result of the temperature-independent susceptibility.

Electronic Structures of the Filled Tetrahedral SemiconductorLiMgN with a Zincblende-Type Structure

An ab initio method with mixed-basis norm-conserving non-localpseudo-potentials has been employed to investigate the electronicstructures of LiMgN. The band structure, electronic density of statesand charge density contour plot of LiMgN are also presented. By thecalculation, we have found that LiMgN with a zincblende-type structurewas an indirect gap semiconductor, and the value of indirect(Γ-X) energy band gap under the local density approximation was2.97 eV. In addition, the strong covalent character for Li-N and Mg-Nhas also been found in LiMgN.