Tellurium Sites Research Articles

Host isotope effects on the oxygen local vibrations in CdTe

Strong absorption peak observed near 350 cm−1 in the infrared spectrum of CdTe is assigned to a localized vibrational mode of 16O impurity atoms at tellurium sites. In this work, we studied the nature of these vibrations in terms of the effect of isotopic mass variations in the nearest neighbor Cd atoms. We showed that Cd atoms with 8 stable natural isotopes of varying abundances cause the observed line shape in the observed localized vibrational absorption peak. To calculate the effect of isotopic mass variations, we used the XY4 molecular model, X being the impurity atom at a host Te atom site and Y’s are various isotopes of the host Cd atoms. Corresponding frequencies of local modes were calculated for each possible combinations of neighboring Cd atoms. For an XY4 molecule with Td symmetry, only the triply degenerate mode is infrared active. The energies of this mode are higher than those of the others. This mode is possible only when all neigboring Cd atoms are the same isotope. To simulate the absorption data, we used a dynamical matrix approach where a force constant is given for each of the bending and stretching potential energy terms. By diagonalization of the dynamical matrix we were able to fit the calculated spectrum to the data with a proper choice of the bending and stretching force constants. A good agreement with the experiment as well as reported force constants for other impurities in CdTe is obtained.

Role of Tellurium Ions for Electrochemically Synthesized Zinc Telluride 2D Structures on Nonconductive Substrate

AbstractAlthough electrodeposition has emerged as a promising approach to make metal chalcogenide nanostructures, it has an underlying issue of exfoliating the deposits affixed to a conductive substrate, which is inevitable to transfer electrons for a reduction reaction, for precise characterization and advanced device fabrication. Herein, direct electrodeposition of metal chalcogenides on a silicon dioxide (SiO2) insulator and its device applications for a back‐gated field‐effect‐transistor and a nitrogen dioxide gas sensor are investigated. Tellurium metal nanorods are deposited on SiO2 by the redox reaction of tellurium substances in the electrolyte. Using underpotential deposition, zinc telluride (ZnTe) is propagated onto tellurium sites, which has deposited on SiO2, bridging the microgap electrode on SiO2. The growth mechanisms of ZnTe on the SiO2 are also explored. This finding addresses the major challenge associated with the electrodeposition by the successful deposition of complex chalcogenides on an insulating substrate that expands its applications in fields for advanced electronics.

Acoustic and acousto-optic properties of Ge-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- and Si-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- glasses in case diffraction on longitudinal and shear acoustic waves

We investigated acoustic and acousto-optic properties of glasses based on germanium, selenium, silicon and tellurium. The results of measurement are presented for two group of glasses including germanium, selenium and tellurium (GeSeTe) and silicon and tellurium (SiTe). The major characteristics of glasses such as the velocity of longitudinal and shear acoustic waves as well as the values of figure of merit are presented. The values of figure of merit are obtained by diffraction on longitudinal and shear acoustic waves at the wavelength of optical radiation λ = 3.39 μm. We also present the results of measurements of acoustic attenuation values α for longitudinal and shear acoustic waves in tellurium glasses at ultrasound frequencies in the range f = 75-100 MHz. Keywords: acousto-optics, acousto-optic figure of merit, germanium, selenium, silicon, tellurium, attenuation acoustic waves.

Submonolayer copper telluride phase on Cu(111): Ad-chain and trough formation

A new surface telluride phase on Cu(111) is revealed and structurally characterized with picometer accuracy by a concerted application of LEED-IV, STM, and DFT. It is demonstrated that tellurium interacts strongly with the surface, inducing a complex displacive reconstruction in order to increase the number of available tellurium sites. This finding suggests that the CuTe/Cu interfaces that are used in photovoltaic cells might also be of equally complex structure.

Trash to treasure: From construction waste to tellurium adsorbent materials

Solid waste, such as construction waste, electric and electronic equipment wastes, has become one serious global challenge due to the presence of toxic substances and non-biodegradable substances in it. Recycling valuable resources from these solid wastes is essential for circular economy and sustainable development strategies due to the valuable elements and potential environmental risks of solid waste. Herein this work presents a promising method for fabrication of high-effective adsorption material using construction waste as raw materials, promising for coarse tellurium extraction from photovoltaic waste. At first stage, porous ceramic particles were obtained by ball milling, acid treatment, and calcination of brick powder. Then, the layered double hydroxides-activated brick mass (LDH-ABM) with high tellurium adsorption properties were fabricated by coating of ceramic particles with a layer of Al2O3 and subsequent hydrothermal growth of LDH nanosheets. The results indicated that the LDH-functionalized brick particles were assembled by LDH nanoplates, which was favorable for efficient tellurium ions transport into the internal part of adsorbents. The micro/nanoscale hierarchical structures of the LDH-ABM along with their porous nature and high specific surface also make them have excellent tellurium adsorption ability. In addition, the adsorption ability can be recovered by the economically sustainable regeneration process. The high tellurium adsorption capacity was attributed to the large surface of porous brick particles which provides more tellurium adsorption sites by reducing the nanoplates aggregation. The controlled process presented here provides an effective way to fabricate functional adsorbent using construction waste as raw material for potential application in tellurium extraction.

Synergism of tellurium-rich structure and amorphization of NiTe1+x nanodots for efficient photocatalytic H2-evolution of TiO2

The exploitation and design of novel low-cost cocatalysts with rich H2-evolution active centers is quite crucial for markedly promoting the photocatalytic activity. Herein, tellurium-rich amorphous NiTe1+x nanodots as a novel and robust H2-generation cocatalyst were ingeniously loaded onto the TiO2 to greatly improve its photocatalytic H2-evoluton performance via a synergistic strategy of tellurium-rich structure and amorphization, with an aim of maximally exposing more H2-evolution site of tellurium atoms. In this case, tellurium-rich amorphous NiTe1+x nanodots were very small (0.3–1 nm) and uniformly modified onto the TiO2 by the facile photoinduced synthesis route, and the resultant a-NiTe1+x/TiO2(0.5 wt%) achieves the highest H2-evolution rate (3302 μmol h−1 g−1, AQE = 15.8 %). The superior activity can be attributed to the successful deposition of tellurium-rich amorphous NiTe1+x nanodots, which can not only efficiently enhance the photoinduced electron migrate from TiO2, but also supply abundant active tellurium sites to accelerate the interfacial H2-evolution process. Significantly, the tellurium-rich a-NiTe1+x can also be utilized as the universal cocatalyst. This research may provide new avenues to develop efficient and low-cost cocatalysts with abundant enriched active-sites for high performance photocatalysts.

Акустические и акустооптические свойства стекол Ge-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- и Si-=SUB=-a-=/SUB=-Se-=SUB=-b-=/SUB=-Te-=SUB=-c-=/SUB=- в случае дифракции на продольных и сдвиговых акустических волнах

We investigated acoustic and acousto-optic properties of glasses based on germanium, selenium, silicon and tellurium. The results of measurement are presented for two group of glasses including germanium, selenium and tellurium (GeSeTe) and silicon and tellurium (SiTe). The major characteristics of glasses such as the velocity of longitudinal and shear acoustic waves as well as the values of figure of merit are presented. The values of figure of merit are obtained by diffraction on longitudinal and shear acoustic waves at the wavelength of optical radiation λ = 3.39 µm. We also present the results of measurements of acoustic attenuation values α for longitudinal and shear acoustic waves in tellurium glasses at ultrasound frequencies in the range f = 75-100 MHz.

Local Structure and Anti-Structural Defects of Tin in Amorphous and Crystalline Ge2Sb2Te5 Films

The absorption Mossbauer spectroscopy on 119Sn impurity centers shows that germanium atoms in the structure of amorphous and polycrystalline Ge2Sb2Te5 films have different local symmetries (tetrahedral in the amorphous phase and octahedral in the crystalline). By emission Mossbauer spectroscopy on 119mSn impurity centers formed after the radioactive decay of 119Sb or 119mTe parent atoms, tin antisite defects at antimony and tellurium sites of crystalline Ge2Sb2Te5 films are identified.

125Te spin-lattice relaxation in a candidate to Weyl semimetals WTe2

The tungsten ditelluride WTe2 was suggested to belong to the Weyl semimetal family. We studied 125Te spin-lattice relaxation and NMR spectra in a WTe2 single crystal within a large range from 28 K up to room temperature. Measurements were carried out on a Bruker Avance 500 NMR pulse spectrometer for the crystalline c axis directed in parallel and perpendicular to the magnetic field. Relaxation proved to be single-exponential. The relaxation time varied depending on the sample position in magnetic field and frequency offset. The relaxation rate increased about linearly with temperature below 70 K, however the dependence became nearly quadratic at higher temperatures. The relaxation rate within the total temperature range was fitted using a theoretical model developed in Ref. [41] for Weyl semimetals and assuming the decrease of the chemical potential with increasing temperature. The results obtained for 125Te spin-lattice relaxation evidence in favor of the topological nontriviality of the WTe2 semimetal. The 125Te NMR spectra agreed with the occurrence of nonequivalent tellurium sites and varied insignificantly with temperature.

Electrocatalytic Nitrogen Fixation on Metal Tellurides Boosted by Multiple Promoted-Synergetic Effects of Telluride

Summary To date, the development of the nitrogen reduction reaction (NRR) electrocatalysts to achieve high ammonia production at low overpotentials is insufficient. Here, Sb2Te3 displays notable electrochemical NRR performance at 0 V (versus RHE), with an ammonia yield rate of 13.8 μg h−1 cm−2 and a faradic efficiency of 27.7% (the highest yield rate at low overpotentials reported, to the best of our knowledge). Sb2Te3 is also stable over 50 h. Density functional theory (DFT) calculations disclose that there are multiple promoted-synergetic effects in telluride. Tellurium sites can modulate the electronic structure of catalysts to drive nitrogen adsorption on antimony sites. Tellurium sites also allow surface hydrogenation to suppress hydrogen evolution, facilitate the reduction of nitrogen into ∗NNH (the rate-determining step) in NRR, and accelerate the desorption of NH3. The other tellurides (CoTe2, CdTe, and Bi3Te4) also show high NRR performance at low overpotentials, implying that such multiple promoted-synergism may be generalized.

Local vibrational modes of natural isotopes of substitutional oxygen in CdTe

We investigated the localized vibrational modes (LVM) of natural oxygen containing $^{16}$O, $^{17}$O, and $^{18}$O isotopes at a substitutional tellurium site in cadmium telluride using infrared absorption spectroscopy at cryogenic temperatures. The main absorption peak observed at 350 cm$^{-1\, }$was formerly attributed to a fundamental LVM mode ($\nu _{0})$ of oxygen at a tellurium site. The relatively weak absorption peaks observed at 331 cm$^{-1\, }$and 340 cm$^{-1\, }$are assigned as the same $\nu_{0}$ mode of the $^{17}$O and $^{18}$O isotopes, respectively, based on their relative intensities and spectral positions. The spectral positions were confirmed with theoretical calculations using a linear chain model where the peak position at 350 cm$^{-1}$ was taken as the reference for the $^{16}$O isotope. From a least square analysis of the observed peak positions we were able to calculate the force constants from perturbation theory. A Lorentzian line shape analysis of each $\nu_{0}$ absorption peak, considering the effects of isotopic mass and natural abundance variations of the host Cd atoms, was also carried out to further confirm their assignments. Reasonably good line shape fittings were obtained for $\nu _{0}$ modes of all isotopes of oxygen.

The crystal structure of a new CdTe2O5 polymorph, isotypic with ∊-CaTe2O5.

Single crystals of cadmium penta-oxidoditellurate(IV), CdTe2O5, were obtained as by-products in a hydro-thermal reaction of Cd(NO3)2·4H2O, TeO2, H6TeO6 and NH3 (molar ratios 2:1:1:6) at 483 K for seven days. The crystals represent a different polymorph (henceforth referred to as the β-form) than the α-CdTe2O5 crystals grown from the melt, and are isotypic with hydro-thermally grown ∊-CaTe2O5. The asymmetric unit of β-CdTe2O5 comprises one Cd, two Te and five O sites, all of which are located in general positions (Wyckoff position 4 e). The cadmium(II) atom is coordinated by seven oxygen atoms, forming 2 ∞[CdO6/2O1/1] (100) layers. Both tellurium sites are surrounded by four oxygen atoms with one of them being at a significantly longer distance than the other three. The resulting bis-phenoidal [TeO4] units also form layers propagating parallel to (100) by sharing edges with each other. The stereochemically active 5s 2 lone pair of the TeIV atoms leads to the formation of large channels extending along [011] and smaller ones along [010]. A qu-anti-tative comparison between the crystal structures of β-CdTe2O5 and ∊-CaTe2O5 is made.

Growth and structural characterization of BiSbTe3-ySey single crystals

Bi2Te3, Sb2Te3, and their intermixtures are classical topological insulators with relatively simple electronic band structure. These materials are well known for their near room temperature thermoelectric effect too. The tuning of the Fermi level is considered relatively easy in these materials to achieve bulk insulating character. This study aims at the preparation of BiSbTe3 with isovalent selenium substitution at tellurium site to form BiSbTe3-ySey(0 ⩽ y ⩽ 2.5) solid solutions. Single crystals of BiSbTe3-ySey (BSTS) were synthesized using the modified Bridgman technique. X-ray diffraction studies and morphological analysis confirmed the formation of high-quality single crystals with a rhombohedral crystal structure in the R3m phase. The lattice parameters were found to decrease monotonically with an increase in the selenium concentration. The lattice volume for the composition BiSbTe3 was 497.94 Å3, which decreased to 432.90 Å3 for the last composition BiSbTe0.5Se2.5. Energy Dispersive X-ray Spectroscopy confirmed the homogeneous distribution of the elements in the sample and its chemical composition.

Antisite Defects in Ge–Te and Ge–As–Te Semiconductor Glasses

The formation of antisite defects in Ge20Te80 and Ge15As4Te81 vitreous alloys in the form of tin atoms in tellurium sites and tellurium atoms in germanium sites is shown by emission Mossbauer spectroscopy with the 119mmSn(119mSn), 119mTe(119mSn), 125Sn(125Te), and 125mTe(125Te) isotopes. It is shown that the isovalent substitution of germanium atoms by tin atoms does not vary the symmetry of the local surrounding of germanium sites, while tin and tellurium atoms reconstruct their local surrounding in sites unnatural for them.

Антиструктурные дефекты в полупроводниковых стеклах Ge-Te и Ge-As-Te

AbstractThe formation of antisite defects in Ge_20Te_80 and Ge_15As_4Te_81 vitreous alloys in the form of tin atoms in tellurium sites and tellurium atoms in germanium sites is shown by emission Mössbauer spectroscopy with the ^119 mm Sn(^119 m Sn), ^119 m Te(^119 m Sn), ^125Sn(^125Te), and ^125 m Te(^125Te) isotopes. It is shown that the isovalent substitution of germanium atoms by tin atoms does not vary the symmetry of the local surrounding of germanium sites, while tin and tellurium atoms reconstruct their local surrounding in sites unnatural for them.

ЯМР-исследование полуметалла Вейля WTe-=SUB=-2-=/SUB=- ниже температуры топологического перехода

We carried out 125Te NMR studies of a WTe2 topological Weyl semimetal at temperatures of 41 and 293 K. Measurements were performed using a pulse Bruker Avance 500 NMR spectrometer. 125Te NMR spectra were obtained for the WTe2 single crystal at the orientation of the crystalline c axis parallel and perpendicular to the quantized field. We ascribed the complex spectra to four non-equivalent tellurium sites in the WTe2 crystalline structure. The recovery of the longitudinal magnetization was studied after the pulse saturation of particular lines in the spectra. We observed the single-exponential relaxation. The frequency shifts and widths of the spectral lines differed insignificantly at two temperatures while the spin-lattice relaxation times at 41 K were by a factor of approximately 30 greater than the relevant times at room temperature. Strong temperature dependence of relaxation was suggested to be due to the contribution of Weyl quasi-particles below the topological phase transition.

Structural and optical properties of oxygen doped single crystal ZnTe grown by multi-tube physical vapour transport

Bulk single crystals of zinc telluride up to 10 mm thick have been grown by the Multi-Tube Physical Vapour Transport technique and doped, in-situ during growth, with oxygen. Following hetero-epitaxial nucleation and buffer growth on 100 mm diameter GaAs seed wafers, oxygen was introduced to the quartz growth envelope, using nitrous oxide as a precursor, via a novel gas injection system. Mass spectra from a residual gas analyser sampling the gases exiting the growth envelope indicated that the nitrous oxide had been cracked at the operating temperature of the furnace releasing oxygen into the growth region. The structural perfection of the grown crystals was assessed by synchrotron based X-ray diffraction measurements and found to be extremely high, improving significantly with distance from the seed. Rocking curve widths, measured over a 4 mm × 7 mm area, as low as 20 arcsec were observed. No evidence was found for a reduction in crystalline quality resulting from the incorporation of oxygen. Luminescence studies (4–300 K) showed strong red luminescence at 680 nm persisting up to room temperature indicating that oxygen had been incorporated substitutionally onto tellurium sites. This material is highly transparent at the red emission wavelength with absorption coefficients of approximately 2 cm−1. Under alpha radiation from a 241Am source, scintillation was observed from the doped material with approximately 12,700 photons/MeV and a full width at half height maximum of 27%. The material is a potential candidate for large volume scintillation based radiation detectors.

Tellurium bonding in amorphous Ge2Sb2Te4, Ge2Sb2Te5 and Ge2Sb2Te7: A 125Te NMR investigation

We have investigated the frequency-space nuclear magnetic resonance spectrum of 125Te in the amorphous forms of Ge2Sb2Tex (x=4,5, and 7). The results indicate that there is one distinct tellurium site in the a-Ge2Sb2Te4 and a-Ge2Sb2Te7 and two tellurium sites in the a-Ge2Sb2Te5. The width of the frequency-space spectra suggests that there is significant disorder about the average site for all cases. In light of recent extend X-ray absorption fine structure results, the a-Ge2Sb2Te4 and a-Ge2Sb2Te7 spectra may be the nuclear magnetic resonance fingerprint of three and twofold coordinated tellurium, respectively. The a-Ge2Sb2Te5 spectrum can be reproduced reasonably well with Gaussian components that are very similar to those components needed to model the a-Ge2Sb2Te4 and a-Ge2Sb2Te7 data. These consistencies in the modeling strongly suggest that the average Te structural units occurring in the latter two compounds are the most prominent Te sites in a-Ge2Sb2Te5.

Oxygen-doped ZnTe phosphors for synchrotron X-ray imaging detectors

ZnTe:O powder phosphors were successfully prepared by a dry synthesis process using gaseous doping and etching media. It was found that dry doping by O2 through ball-milling was an effective way to synthesize ZnTe:O powder phosphors and produced a red emission centered at 680 nm with a decay time of 1.1 µs. The emission intensity of dry O2-doped samples was three times more intense than from ZnO-doped samples, possibly due to a more uniform distribution of oxygen substitution on tellurium sites. The samples annealed in a 95% N2/5% H2 forming gas atmosphere exhibited a x-ray luminescent efficiency five times higher than did powders annealed in vacuum or N2 atmosphere. This enhancement was attributed to the removal of surface tellurium oxides. ZnTe:O phosphor screens were prepared with x-ray luminescence efficiencies equivalent to 56% of ZnSe:Cu,Ce,Cl and 76% of Gd2O2S:Tb screens under 17-keV radiation. An x-ray imaging resolution of 2.5 lines/mm was resolved, the same as that measured for commercial ZnSe:Cu,Ce,Cl and Gd2O2S:Tb screens. These results indicate that ZnTe:O is a promising phosphor candidate for synchrotron x-ray imaging applications.

Oxotellurate(IV) der Lanthanide: II. Die isotype Reihe M2Te5O13 (M = Dy – Lu) / Oxotellurates(IV) of Lanthanides: II. The Isotypic Series M2Te5O13 (M = Dy – Lu)

For the shortly discovered formula type M2Te5O13 (triclinic, P1̄), the establishment of an isostructural series in the last third of the lanthanide family (M = Dy - Lu) was possible. The excessive formula unit TeO2 additional to the well-known composition M2Te4O11 (monoclinic, C2/c) leads to the slicing of the [M2O10]14− layers which are typical for the tellurium-oxide poorer compounds. By coupling together the bicapped trigonal prismatic (M1, CN = 8) and the pentagonal bipyramidal (M2, CN = 7) lanthanide-oxygen polyhedra via edges, [M4O20]28− bands are formed stretching along the a axis and piling up to a primitive rod-packing. The linkage of these bands occurs parallel to the (010) plane via Te3 as well as via Te4 parallel to (100). Besides the usual 3+1 coordination, two of the five crystallographically independent tellurium sites are coordinated regularly fourfold (d(Te−O) ≈ 186−213 pm) and even 3+2-fold by oxygen atoms. The tellurium-oxygen polyhedra form corrugated layers running parallel to (101) which follow so close to each other that the tellurium-oxygen partial structure appears to be almost three-dimensional at a passing glance. As in M2Te4O11-type representatives, the non-bonding electron pair (lone pair) of each Te4+ cation shows stereochemical activity which always appears to flock together in large tellurium neighboured positions.