ZnTe Alloys Research Articles

Effect of Mg substitution on structural, electronic, optical and thermoelectric properties of ZnTe alloy

In the present work, we study the structural, electronic, optical and thermoelectric properties of Zn1−xMgxTe compounds with different Mg concentrations (x = 0.0, 0.25, 0.50 and 0.75). These calculations were investigated through the density functional theory (DFT) by using the GGA approach with the Perdew-Burke-Ernzerh (PBE) of exchange correlation. The obtained results of the electronic properties show that Zn1−xMgxTe (x = 0.0, 0.25, 0.50 and 0.75) alloys are semiconductor materials with a direct band gap at the Γ-symmetry point. In fact, the optical results indicate that Zn1−xMgxTe compounds are good candidates for photovoltaic applications due to their strong absorption in the visible region. In addition, the main thermoelectric coefficients such as Seebeck coefficient (S), electrical conductivity over relaxation time (σ/ τ), thermal conductivity over relaxation time (k/ τ), power factor (PF) and the figure of merit (ZT) were investigated.

Fabrication and investigation of zinc telluride thin films

Zinc Telluride ZnTe alloys and thin film have been fabricated and deposited on glass substrates by thermal evaporation method which may be a suitable window layer of zinc telluride with different annealing temperatures (373 and473) K for 60 minutes in vacuum. Deposited thin films with thickness 100 nm was characteristic by using X-ray diffraction XRD to know structures, Atomic Force Microscopy (AFM) to evaluate surface topology, morphology. It was found out that the vacuum annealing improves on thin ZnTe films structure and surface morphology. Structural analysis reveals that ZnTe films have zinc blende structure of cubic phase with (111) preferred reflection and grain size is enhanced from 8.6 to 16.7 nm with annealing. Optical properties where optical bandgap energy values slightly decreased (2.3-2.2) eV as the annealing temperatures.

Zinc Telluride as Electrochemical Storage Material for High-Performance Sodium-Ion Batteries.

High-energy ball milling (HEBM) is used to synthesize zinc telluride (ZnTe) and amorphous C (ZnTe-C) nanocomposites as novel anode materials for sodium-ion batteries (SIBs). A nanostruc-tured ZnTe-C composite is prepared using Zn, Te, and acetylene black as precursor materials via a facile two-step HEBM process. The initial HEBM of Zn and Te induces the formation of the ZnTe alloy nanostructure via a mechanochemical reaction. The subsequent HEBM process generates the ZnTe composite embedded in amorphous C (ZnTe-C), as confirmed using X-ray diffraction, transmission electron microscopy, and element mapping analyses. When used as SIB anode, the ZnTe-C composite exhibits good cyclic life (specific discharge capacities of 383 mAh g-1 at 0.1 A g-1 over 150 cycles and 373 mAh g-1 at 0.5 A g-1 after 500 cycles) and excellent rate capability (89% capacity retention at 10 A g-1 relative to that at 0.1 A g-1). The impedance analysis and ex situ scanning electron microscopy results reveal that the properties of ZnTe-C are superior to those of ZnTe because C serves as buffering matrix that suppresses the volume changes in ZnTe during alloying/dealloying and reduces the charge transfer resistance. The ZnTe-C nanocomposite in this study is a promising candidate for high-performance SIB anodes.

ДОСЛІДЖЕННЯ ФАЗОВОЇ РІВНОВАГИ СПОЛУК ЦИНК-ТЕЛУР ДЛЯ УДОСКОНАЛЕННЯ ВЛАСТИВОСТЕЙ ФУНКЦІОНАЛЬНОГО МАТЕРІАЛУ РАДІАЦІЙНИХ СЕНСОРІВ

The phase equilibrium studies of ZnTe compounds are studied in order to improve the properties of one of the main functional materials of radiation sensors. To control the properties of GdZnTe compounds as the most promising materials for radiation diagnostics, it is necessary to ensure the quality and control of the parameters of the compounds from which it is technologically made. A comparative evaluation of the possibilities of using the considered binary compounds to create semiconductor sensors shows their advantages in comparison with elementary semiconductors. Among binary compounds, GdTe has undoubted advantages. However, this material cannot solve all the problems and eliminate the known shortcomings of existing semiconductor sensors. Such capabilities have solid solutions of broadband compounds, among them the most promising GdTe - ZnTe, forming wideband solid solutions of Gd x Zn 1-xTe (CCT or CZT). Technologically determined areas of temperature and partial pressure of zinc over ZnTe systems. Processional changes of lattice parameters in ZnTe alloys. Precise measurements of the lattice parameter in ZnTe alloys saturated with Zn and Te, respectively, showed that the lattice constant of alloys equal to 6.1026 ± 0.0001 Å practically does not change. The region of homogeneity, according to experimental data on vapor pressure should not exceed 0.2 at.%.

Intermediate Band Studies of Substitutional V2+, Cr2+, and Mn2+ Defects in ZnTe Alloys

We present first-principles total-energy density functional calculations to study the intermediate band states of substitutional V2+, Cr2+, and Mn2+ ions in ZnTe alloys. The intermediate band states of substitutional transition metal defects of TM2+xZn1−xTe (TM = V, Cr, Mn) alloys are examined as their atomic, structural, and electronic analysis. Our findings show that the scissor-corrected transitions due to Jahn-Teller effects lead to the wavelengths 2530 nm and 2695 nm in the emission spectra. Our findings agree with previously reported experimental results.

Enhanced Lithium Ion Storage by Titanium Dioxide Addition to Zinc Telluride-Based Alloy Composites.

A nanostructured ZnTe-TiO₂-C composite is synthesized, via a two-step high-energy mechanical milling process, for use as a new promising anode material in Li-ion batteries (LIBs). X-ray diffraction and X-ray photoelectron spectroscopy results confirm the successful formation of ZnTe alloy and rutile TiO₂ phases in the composites using ZnO, Te, Ti, and C as the starting materials. Scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy mapping measurements further reveal that ZnTe and TiO₂ nanocrystals are uniformly dispersed in an amorphous carbon matrix. The electrochemical performances of ZnTe-TiO₂-C and other control samples were investigated. Compared to ZnTe-TiO₂ and ZnTe-C composites, the ZnTe- TiO₂-C nanocomposite exhibits better performance, thereby delivering a high reversible capacity of 561 mAh g-1 over 100 cycles and high rate capability at a high current density of 5 A g-1 (79% capacity retention of its capacity at 0.1 A g-1). Furthermore, the long-term cyclic performance of ZnTe-TiO₂-C at a current density of 0.5 A g-1 shows excellent reversible capacity of 528 mAh g-1 after 600 cycles. This improvement can be attributed to the presence of a TiO₂-C hybrid matrix, which acts as a buffering matrix that effectively mitigates the large volume changes of active ZnTe during repeated cycling. Overall, the ZnTe-TiO₂-C nanocomposite is a potential candidate for high-performance anode materials in LIBs.

The structural, electronic, magnetic, and optical properties of the Cr-, Mo-, and W-doped ZnTe alloys

The first-principle method is adopted to study doping of different atoms X (X = Cr, Mo, or W) in ZnTe compound. The spin-down bandgaps of the X-doped Zn0.96875X0.03125Te alloys are 1.368, 1.415, and 1.399 eV for X = Cr, Mo, and W, respectively. All the doped Zn0.96875X0.03125Te (X = Cr, Mo, or W) alloys presents half-metallic (HM) feature, which is different from the ZnTe semiconductor, thus the doped HM alloys are the potential materials for spintronic applications. The Cr-3d(t2g) and Te-5p spin-up states of the Zn0.96875Cr0.03125Te alloy intersect the Fermi level, but only the Mo-4d(t2g) and W-5d(t2g) spin-up states of the Zn0.96875Mo0.03125Te and Zn0.96875W0.03125Te alloys, respectively, intersect the Fermi level. For the Zn0.96875Cr0.03125Te alloy, the double-degenerate $$d_{yz}$$ and $$d_{xz}$$ spin-up states of Cr atom are occupied, but the undegenerated $$d_{xy}$$ states of Cr atom are unoccupied. But for Zn0.96875X0.03125Te (X = Mo or W) alloys, the threefold degenerate $$d_{xy}$$ , $$d_{yz}$$ , and $$d_{xz}$$ states of X atoms are half-occupied. All the X-doped Zn0.96875X0.03125Te (X = Cr, Mo, or W) alloys are magnetic with the total magnetic moments of 4.000 $$\mu_{{\text{B}}}$$ mainly contributed by the X atom and neighboring Te atoms. The doped Zn0.96875X0.03125Te (X = Cr, Mo, or W) alloys have promising applications in infrared devices.

Efficient TiC-C hybrid conductive matrix for ZnTe anode in Lithium-ion storage

ZnTe alloy is simply prepared by the primary annealing step, along with the formation of TiC-C hybrid conductive matrix in the secondary ball-milling process. As-prepared ZnTe@TiC-C nanocomposite consists of active ZnTe nanocrystallites embedded in a TiC-C buffering material, which is adopted as a potential anode material for Lithium-ion storage. In comparison with stand-alone carbon matrix as a buffering material, the presence of the TiC-C hybrid matrix improves the electrochemical performances of ZnTe active material in terms of capacity, stability, reversibility, and rate capability performances. Also, the optimum content of TiC in the ZnTe@TiC-C composites is evaluated based on the electrochemical performances, in that the ZnTe@TiC(20%)-C composite exhibits the highest reversible capacities of ~547 mAh g−1 after 300 cycles at 0.1 A g−1, the good rate capability (84% capacity retention at 10 A g−1 when compared with the capacity at 0.1 A g−1), and the cycle life at 1 A g−1 (~700 mAh cm−3 after 500 cycles). The enhanced electrochemical performance of the ZnTe active material with the presence of the TiC-C hybrid matrix can be attributed to the effective mitigation against the large volume change in the ZnTe and the high conductivity, thereby facilitating electron transport during prolonged cycling.

The electronic and magnetic properties of the Mo doped ZnTe alloys with different configurations

The electronic and magnetic properties of the Mo doped ZnTe alloys with five different configurations were studied by using first-principles calculations. The ground states of doped alloys with four configurations were ferromagnetic states, and only one doped alloy favored in antiferromagnetic state. All the Mo-doped Zn0.9375Mo0.0625Te alloys with five configurations were half-metallic, hence they were potentially good materials to make practical spintronic devices. The Zn0.9375Mo0.0625Te alloy with shortest atomic distance between the two doped Mo atoms (dMo–Mo) presented three obvious peaks and one very small spin-up peak near the Fermi level in total density of states and showed two isolated occupied bands and one isolated un-occupied spin-up band in band structure, which was different from the rest alloys with longer dMo–Mo. In all the Zn0.9375Mo0.0625Te alloys with five configurations, the occupied dz2 and dx2-y2 double degenerate states of the Mo atoms showed the similar feature, but the dxy, dyz, and dxz states showed different occupying feature. The Mo-doped Zn0.9375Mo0.0625Te alloys either in the ordered doped manner with one configuration or in the disordered manner with more than one configurations were ideal materials, which can also be seen from the similar total magnetic moments and atomic magnetic moments of the two Mo atoms in five alloys.

Extensive investigations of photon interaction properties for ZnxTe100-x alloys

Abstract An extensive investigation of photon interaction properties has been made for ZnxTe100-x alloys (where x = 5, 20, 30, 40, 50) to explore its possible use in sensing and shielding gamma radiations. The results show better and stable response of ZnTe alloys for various photon interaction properties over the wide energy range, with an additional benefit of ease in fabrication due to lower melting points of Zn and Te. Mass attenuation coefficient values show strong dependence on photon energy as well as composition. Effective atomic number has maximum value for Zn5Te95 and lowest for Zn50Te50 in the entire energy region. The alloy sample with maximum Zeff shows minimal value of Ne and vice versa. Mean free path follows inverse trend as observed for mass attenuation coefficient. The exposure and energy absorption buildup factors depend upon photon energy, penetration thickness and composition (effective atomic number) of ZnxTe100-x alloys. It finds its application for sensing and shielding from highly energetic and highly penetrating photons at sites where radioactive materials were used and visibility of material is not a big constraint. Further, energy down conversion property of ZnTe alloys with subsequent emission in green band suggests its potential use in sensing gamma photons.

Study of the Influence of Annealing Temperature on the Structural and Optical Properties of ZnTe Prepared by Vacuum Thermal Evaporation Technique

The ZnTe alloy was prepared as deposited thin films on the glass substrates at a thickness of 400±20 nm using vacuum evaporation technique at pressure (1 × 10-5) mbar and room temperature. Then the thin films under vacuum (2 × 10-3 mbar) were annealing at (RT,100 and 300) °C for one hour. The structural properties were studied by using X-ray diffraction and AFM, the results show that the thin films had approached the single crystalline in the direction (111) as preferred orientation of the structure zinc-blende for cubic type, with small peaks of tellurium (Te) element for all prepared thin films. The calculated crystallite size (Cs) decreased with the increase in the annealing temperature, from (25) nm before the annealing to (21) nm after the annealing. The images of atomic force microscopy of all thin films appeared a homogenous structure and high smoothness through roughness values ​​that increased slightly from (1.4) nm to (3.4) nm. The optical properties of the ZnTe at (RT,100 and 300) °C were studied transmittance and absorbance spectrum as a function of the wavelength. The energy gap was found about (2.4) eV for the thin films before the annealing and increased slightly to (2.5) eV after annealing at 300 °C

Effect of vacuum annealing on structural and optical properties of nanocrystalline ZnTe thin films

In present study, dependence of structural and optical properties of nanocrystalline $$\hbox {Zn}_{40}\hbox {Te}_{60}$$ (ZnTe) thin films on vacuum thermal annealing has been investigated. ZnTe alloy was prepared by melt quenching technique and thermally evaporated on cleansed glass substrates to deposit thin films. These films were annealed in vacuum ( $$\sim 1\times 10^{-3}$$ mbar) for an hour at three different temperatures 100, 200 and 300 °C. X-ray diffraction results revealed the presence of cubic ZnTe phase in all the films along with some hexagonal Te phase. The crystallite size of ZnTe thin films improved on annealing with larger size at elevated temperatures (from 32 to 80 nm). Micro strain and dislocation density reduced owing to improvement in crystallinity after annealing. The IR transmittance increased with increase in annealing temperature. Field emission scanning electron microscopy images suggested the formation of smooth and uniform thin films with thickness of $$\sim$$ 480 nm. Optical properties revealed the decrease in transmittance and absorption edge shift due to crystallinity improvement on annealing. The optical band gap decreased from 1.37 to 0.91 eV on annealing. Experimental results show that thermal annealing has significant impact on structural and optical properties of ZnTe thin films.

Structural, electronic, magnetic and optical properties of semiconductor Zn1−xMoxTe compound

The structural, electronic, magnetic and optical properties of the Zn1−xMoxTe (x = 0.00, 0.25, 0.50, 0.75, 1.00) have been investigated by the spin-polarized first-principles calculations. The Zn0.50Mo0.50Te has tetragonal structure while the Zn1−xMoxTe (x = 0.00, 0.25, 0.75, 1.00) crystallize in cubic structures. For Zn1−xMoxTe (x = 0.25, 0.50, 0.75, 1.00) alloys, the lattice constant and the volume are found larger than those of pure ZnTe alloy. The Zn1−xMoxTe (x = 0.25, 0.50, 0.75, 1.00) is magnetic and the Mo element is found dominant in the bands crossing the Fermi level in the spin-up channel. The Zn0.75Mo0.25Te and MoTe have half-metallic (HM) behavior. In spin-down channel of the Zn0.75Mo0.25Te, the Zn atom mainly contributed to the conduction band minimum (CBM), while the valence band maximum (VBM) appears mainly due to contribution of Te element. A positive spin splitting and crystal field splitting of d-states of Mo atom has been observed for Zn0.75Mo0.25Te alloy. The maximum values of the absorption coefficients αMAX(ω) of the Zn0.50Mo0.50Te alloy along a or b axes are smaller than the absorption coefficient along c axis. The first absorption peak appearing in the energy range of 0.000–1.000 eV for Zn1−xMoxTe (x = 0.25, 0.50, 0.75 or 1.00) alloys is the new peak which is not observed in ZnTe.

Polarization Dependent Reflectivity and Transmission for Cd1-Xznxte/GaAs(001) Epifilms in the Far-Infrared and Near-Infrared to Ultraviolet Region

The results of a comprehensive experimental and theoretical study is reported to empathize the optical properties of binary GaAs, ZnTe, CdTe and ternary Cd1-xZnxTe (CZT) alloys in the two energy regions: (i) far-infrared (FIR), and (ii) near-infrared (NIR) to ultraviolet (UV). A high resolution Fourier transform infrared spectrometer is used to assess the FIR response of GaAs, ZnTe, CdTe and CZT alloys in the entire composition 1.0 ≥ x ≥ 0 range. Accurate model dielectric functions are established appositely to extort the optical constants of the binary materials. The simulated dielectric functions ei€¥(ω) and refractive indices n~(ω) are meticulously appraised in the FIR → NIR → UV energy range by comparing them against the existing spectroscopic FTIR and ellipsometry data. These outcomes are expended eloquently for evaluating the polarization dependent reflectivity R(λ) and transmission T(λ) spectra of ultrathin CZT/GaAs (001) epifilms. A reasonably accurate assessment of the CZT film thickness by reflectivity study has offered a credible testimony for characterizing any semiconducting epitaxially grown nanostructured materials of technological importance.

Features of the percolation scheme of transformation of the vibrational spectrum with varying alloy composition for Cd(TeSe) and (CdZn)Te alloys with soft bonds

An interpretation of the lattice vibration spectra of mixed II–VI crystals Cd(Te,Se) and (Cd,Zn)Te within the percolation scheme (1-bond→2-modes) of transformation of the vibrational spectrum with varying alloy composition is presented. For two-mode alloy systems, the higher-frequency mode is split into two. For Cd(Te,Se) and (Cd,Zn)Te alloys, CdSe- and ZnTe-like vibrations are characterized by percolation doublets with a split of δ ≈ 8 and 4 cm–1, respectively. For these II–VI alloys with soft bonds, the distributions of oscillator strengths between percolation doublet modes differ from the model representation originally proposed for chalcogenides (Zn,Be)VI with high contrast in the bond stiffness of binary alloy components.

Magnetic properties of Cr doped ZnTe alloy powder

Zn1−xCrxTe (x=0.0 and 0.05) alloy powders were prepared without any detectable secondary phase using a conventional rotating furnace. The magnetization data obtained using VSM reveal the persistence of ferromagnetic behavior at room temperature. From the Arrott plot, the Curie temperature was estimated to be much greater than 300K. The ESR spectroscopy analysis disclosed the existence of Cr in the +2 valence state with d4 configuration. The complete analysis propose that the hysteresis possibly originated from the magnetic short-range ordering of highly Cr rich Zn1−xCrxTe and CrxTe cluster compounds, which exhibit net magnetic moment via superexchange interaction.

Accuracy of existing atomic potentials for the CdTe semiconductor compound

CdTe and CdTe-based Cd(1-x)Zn(x)Te (CZT) alloys are important semiconductor compounds that are used in a variety of technologies including solar cells, radiation detectors, and medical imaging devices. Performance of such systems, however, is limited due to the propensity of nano- and micro-scale defects that form during crystal growth and manufacturing processes. Molecular dynamics simulations offer an effective approach to study the formation and interaction of atomic scale defects in these crystals, and provide insight on how to minimize their concentrations. The success of such a modeling effort relies on the accuracy and transferability of the underlying interatomic potential used in simulations. Such a potential must not only predict a correct trend of structures and energies of a variety of elemental and compound lattices, defects, and surfaces but also capture correct melting behavior and should be capable of simulating crystalline growth during vapor deposition as these processes sample a variety of local configurations. In this paper, we perform a detailed evaluation of the performance of two literature potentials for CdTe, one having the Stillinger-Weber form and the other possessing the Tersoff form. We examine simulations of structures and the corresponding energies of a variety of elemental and compound lattices, defects, and surfaces compared to those obtained from ab initio calculations and experiments. We also perform melting temperature calculations and vapor deposition simulations. Our calculations show that the Stillinger-Weber parameterization produces the correct lowest energy structure. This potential, however, is not sufficiently transferrable for defect studies. Origins of the problems of these potentials are discussed and insights leading to the development of a more transferrable potential suitable for molecular dynamics simulations of defects in CdTe crystals are provided.

Thermodynamic Investigation of Zn-Te Alloys by Calorimetry

Thermodynamic Investigation of Zn-Te Alloys by Calorimetry

Activity Measurements of Zn-Te Alloys by EMF Method

Activity Measurements of Zn-Te Alloys by EMF Method

Electronic structure and phase stability of MgTe, ZnTe, CdTe, and their alloys in theB3,B4, andB8 structures

The electronic structure and phase stability of MgTe, ZnTe, and CdTe were examined in the zinc-blende (B3), wurtzite (B4), and NiAs-type (B8) crystal structures using a first-principles method. Both the band-gap and valence-band maximum (VBM) deformation potentials of MgTe, ZnTe, and CdTe in the B3 structure were analyzed, revealing a less negative band-gap deformation potential from ZnTe to MgTe to CdTe, with a VBM deformation potential increase from CdTe to ZnTe to MgTe. The natural band offsets were calculated taking into account the core-level deformation. Ternary alloy formation was explored through application of the special quasirandom structure method. The B3 structure is found to be stable over all (Zn,Cd)Te compositions, as expected from the preferences of ZnTe and CdTe. However, the (Mg,Zn)Te alloy undergoes a B3 to B4 transition above 88% Mg concentration and a B4 to B8 transition above 95% Mg concentration. For (Mg,Cd)Te, a B3 to B4 transition is predicted above 80% Mg content and a B4 to B8 transition above 90% Mg concentration. Using the calculated band-gap bowing parameters, the B3 (Mg,Zn)Te [(Mg,Cd)Te] alloys are predicted to have accessible direct band gaps in the range 2.39(1.48)--3.25(3.02) eV, suitable for photovoltaic absorbers.