Tellurium Crystals Research Articles

Features of acousto-optic interaction in uniaxial gyrotropic crystals

The features of noncollinear acousto-optic interaction in gyrotropic crystals in the intermediate diffraction regime and the regime of Bragg diffraction were investigated. The dependence of the efficiency of diffraction in gyrotropic paratellurite, tellurium, and quartz crystals on the intensity of the ultrasonic wave, acousto-optic interaction length, and incident-light polarization was investigated. It is shown that the gyrotropy of the crystal is responsible for the appearance of a multiple-peak structure of the Bragg maximum. It has been established that in the case of propagation of incident and diffracted waves in the vicinity of the optical axis of the crystal, the diffraction efficiency is independent of the polarization state of the incident light. The results of theoretical calculations are in agreement with the experimental results obtained for uniaxial crystals.

In vivo and in vitro cloning and phenotype characterization of tellurite resistance determinant conferred by plasmid pTE53 of a clinical isolate of Escherichia coli.

A determinant encoding resistance against potassium tellurite (Te(r)) was discovered in a clinical isolate of Escherichia coli strain KL53. The strain formed typical black colonies on solid LB medium with tellurite. The determinant was located on a large conjugative plasmid designated pTE53. Electron-dense particles were observed in cells harboring pTE53 by electron microscopy. X-Ray identification analysis identified these deposits as elemental tellurium and X-ray diffraction analysis showed patterns typical of crystalline structures. Comparison with JCPDS 4-0554 (Joint Committee on Powder Diffraction Standards) reference data confirmed that these crystals were pure tellurium crystals. In common with other characterized Te(r) determinants, accumulation studies with radioactively labeled tellurite showed that reduced uptake of tellurite did not contribute to the resistance mechanism. Tellurite accumulation rates for E. coli strain AB1157 harboring pTE53 were twice higher than for the plasmid-free host strain. In addition, no efflux mechanism was detected. The potassium tellurite resistance determinant of plasmid pTE53 was cloned using both in vitro and in vivo techniques in low-copy-number vectors pACYC184 and mini-Mu derivative pPR46. Cloning of the functional Te(r) determinant into high-copy cloning vectors pTZ19R and mini-Mu derivatives pBEf and pJT2 was not successful. During in vivo cloning experiments, clones with unusual "white colony" phenotypes were found on solid LB with tellurite. All these clones were Mucts62 lysogens. Their tellurite resistance levels were in the same order as the wild type strains. Clones with the "white" phenotype had a 3.6 times lower content of tellurium than the tellurite-reducing strain. Transformation of a "white" mutant with a recombinant pACYC184 based Te(r) plasmid did not change the phenotype. However, when one clone was cured from Mucts62 the "white" phenotype reverted to the wild-type "black" phenotype. It was suggested that the "white" phenotype was the result of an insertional inactivation of an unknown chromosomal gene by Mucts62, which reduced the tellurite uptake.

Quantum corrections to 2D hole conductivity in a quantum well on $$(10\bar 10)$$

The anomalous positive magnetoresistance of a two-dimensional (2D) layer on Te $$(10\bar 10)$$ is analyzed, and it is shown that this phenomenon can be described within the weak localization theory taking into account the specific features of the band spectrum symmetry of a 2D layer on this tellurium surface and the associated peculiarities in the phase relaxation processes, as well as the existence of several 2D subbands. The main parameters of the theory have been determined, and it has been found that this orientation of the 2D layer is characterized by an extremely high probability of intersubband transitions in elastic scattering, which makes this case qualitatively different from the 2D hole system on the (0001) surface studied previously. The phenomenon is attributed to the difference in the character of electronic states between these crystal interfaces, namely, dangling covalent bonds in the chains making up the tellurium crystal on the (0001) surface, and the disruption of the weaker interchain Van der Waals bonds on the $$(10\bar 10)$$ face representing the cleavage surface. A conclusion is drawn that the wave-state phase-relaxation time in inelastic processes is dominated by electron-electron scattering.

Tellurite resistance and reduction by obligately aerobic photosynthetic bacteria

Seven species of obligately aerobic photosynthetic bacteria of the genera Erythromicrobium, Erythrobacter, and Roseococcus demonstrated high-level resistance to tellurite and accumulation of metallic tellurium crystals. High-level resistance without tellurite reduction was observed for Roseococcus thiosulfatophilus and Erythromicrobium ezovicum grown with certain organic carbon sources, implying that tellurite reduction is not essential to confer tellurite resistance.

Tricaesium Ditellurium Tetravanadium Chloride Tetradecaoxide

The title compound, (CsCl)Cs2(TeV2O7)2, was obtained at 700 K during the crystallization of a mixed tellurium–caesium vanadate using tellurium tetrachloride as a transport agent. The structure consists of stacks of [V2TeO7] sheets alternately separated by layers of caesium atoms and layers of caesium and chlorine atoms. Within the sheets, the V atoms are distributed over two sites: a tetrahedral site containing V5+ ions and a square pyramidal site containing V4+ ions. The Te4+ ion lies within a tetrahedron formed by three O atoms and a lone pair. A maximum in the electron density is observed at the expected position of the lone pair.

Nonlinearity of Current–Voltage Characteristics of Tellurium Single Crystals under Conditions of the Electrotemperature Effect

It is shown, that under the conditions of the electrotemperature effect (ETE) nonlinear sections occur on current–voltage characteristics (CVC) of tellurium crystals with different dependence of current on voltage. The analysis of CVC and differential conduction leads to the conclusion, that the presence of saturation and the dropping section on CVC is stipulated by the exclusion phenomenon in tellurium. The occuring high conductivity under conditions of ETE, i.e. exciting state, characterized by localizability, time stability, significantly nonlinear dependence of current density on electric field intensity, is a Davidov soliton, which plays an important role in the processes of charge and energy transfer. [Russian Text Ignored].

A cryogenic tellurium detector for rare events and gamma rays

In view of a future experiment on double beta decay we have constructed and operated for the first time a bolometric detector made with an ultrapure tellurium crystal of about 2.1 gram. With this detector we have been able to measure high energy gamma rays from various calibration sources with an energy resolution of 2% in the region of neutrinoless double beta decay. The thermal properties of tellurium at very low temperature are determined for the first time in view of the construction of larger detectors.

Infrared two-dimensional acoustooptic deflector using a tellurium crystal

The first single element 2-D acoustooptic (2DAO) laser beam deflector using a tellurium crystal was designed and fabricated for laser wavelength applications from 5 to 20 microm. The giant values of the figure of merit M associated with these two AO interactions equal to 285,000 x 10(-15) s(3)/kg, are between 2 and 3 orders of magnitude higher than germanium, the next best AO material for 10.6 microm. This latter value indicates that acoustic power densities inside the crystal of the order of 0.1 W/mm(2) are sufficient to diffract 100% of the incident light. The experimental data confirm the predicted 13 degrees /25 MHz deflection slope. The theoretical amplitude and frequency modulation characteristics of the 2DAO deflector are also evaluated.

High resolution electron microscopic studies of the oxidation process of ZnTe films

ZnTe films of about 15 nm thickness were prepared by vacuum deposition from ZnTe power onto NaCl substrates heated to 300°C. Zinc oxide particles with a size of 5 nm which were formed on the surface of ZnTe crystals showed no epitaxial relationship with the latter. Tellurium crystals appeared on certain parts of the ZnTe crystals with specific epitaxial relationships such as (0 11 1)[10 10] Te(111)[110] ZnTe and (0 11 1)[10 10] Te(0001)[10 10] ZnTe . Oxidation of the (110) surfaces of ZnTe crystals are slower than for any other plane. Images of the (110) films at an initial stage of oxidation contained faint superlattice fringes of about 0.85 nm spacing. On the basis of the matching between the HREM images and computer simulation images, the origin of the fringes was attributed to a periodic array of Zn vacancies introduced by the diffusion of Zn atoms to the surface of the ZnTe crystal.

High resolution electron microscopic studies of the oxidation process of ZnTe films

ZnTe films of about 15 nm thickness were prepared by vacuum deposition from ZnTe power onto NaCl substrates heated to 300°C. Zinc oxide particles with a size of 5 nm which were formed on the surface of ZnTe crystals showed no epitaxial relationship with the latter. Tellurium crystals appeared on certain parts of the ZnTe crystals with specific epitaxial relationships such as (0111)[1010]Te(111)[110]ZnTe and (0111)[1010]Te(0001)[1010]ZnTe. Oxidation of the (110) surfaces of ZnTe crystals are slower than for any other plane. Images of the (110) films at an initial stage of oxidation contained faint superlattice fringes of about 0.85 nm spacing. On the basis of the matching between the HREM images and computer simulation images, the origin of the fringes was attributed to a periodic array of Zn vacancies introduced by the diffusion of Zn atoms to the surface of the ZnTe crystal.

Nuclear-magnetic-resonance study of crystalline tellurium and selenium.

Nuclear-magnetic-resonance measurements of $^{125}\mathrm{Te}$ and $^{77}\mathrm{Se}$ have been carried out in single crystals of tellurium and selenium, respectively, between room temperature and the melting point ${T}_{m}$. In particular, both the time evolution of the nuclear magnetization in the laboratory frame as well as in the rotating frame, following both broadband and site-selective excitations, have been investigated in detail. In tellurium, the Zeeman spin-lattice relaxation is determined by three different mechanisms: (1) Below 300 K, spin-lattice relaxation is governed by a two-phonon (Raman) process; (2) in the temperature range between about 300 and 450 K, the influence of conduction electrons overcoming the gap energy of 0.30 eV becomes important; (3) above 450 K, the spin-lattice relaxation is due to mobile charged vacancies. From the high-temperature data, the formation energy of a charged vacancy was found to be 0.66 eV. In selenium, on the other hand, the Zeeman spin-lattice relaxation time is essentially caused by a two-phonon (Raman) process over the entire temperature range. In either system, the phonon-induced spin-lattice relaxation shows the same dependence on the crystal orientation relative to the direction of the external field. For T\ensuremath{\ge}0.74${T}_{m}$ in tellurium as well as in selenium, a diffusional contribution to the rotating-frame relaxation rate is observed, arising from fluctuations in the nuclear dipole and chemical shift interaction due to atomic self-diffusion. However, from these data alone the correlation time of atomic motion could be determined only with a relative large error. In contrast, from site-selective excitation experiments the correlation time was extracted directly with a high degree of accuracy without any assumption regarding the nature of the nuclear spin interactions. The observed correlation times are discussed in terms of Mehrer's model for monovacancy diffusion via nearest- and next-nearest-neighbor jumps. Diffusivities in tellurium deduced from this model are in good agreement with the tracer data obtained recently by Mehrer et al. In contrast, the observed diffusion coefficients in selenium are about a factor of 20 smaller than the tracer diffusion coefficients measured some years ago by Br\"atter and Gobrecht.

Determination of the phonon density of states from the thermodynamic functions of the crystal (white tin, antimony, tellurium)

The linear incorrect problem of determining the density of states from the phonon specific heat is solved by A. N. Tikhonov's regularization method for white tin, antimony, and tellurium crystals.

Metal-containing plasma-polymerized films

The preparation of metal-containing plasma-polymerized films by simultaneous plasma polymerization and evaporation of metal is described. The metals tellurium and bismuth, dispersed in plasma polymers derived from CS 2 and styrene, were incorporated in the amorphous state. The amorphous-crystalline phase transformations of tellurium and bismuth were studied by differential scanning calorimetry (DSC). From the results obtained in DSC measurements, the activation energies for crystallization of tellurium and bismuth were estimated to range from 1 to 3 eV. Furthermore, some aspects of their structure are discussed.

Photo-induced complex permittivity measurements of tellurium at 9 GHz

A microwave transmission method to determine the photo-induced complex relative permittivity of semiconductors (photodielectric effect and photoconductive effect) has been investigated. Measurements have been made on single crystal tellurium samples at a temperature of 100 K, at a microwave frequency of 9 GHz in optical frequencies between about 0.7×10 14 and 2.0×10 14 Hz (i.e. wavelengths between 1.5 and 4.2 μm). From the measured data, the relaxation time of the free carriers in the tellurium samples was calculated.

Electron Microscope Investigation of Crystals Based on Bend-Contour Arrangement II. Bending Phenomena of the Crystal Growth in an Amorphous Film

Bend-contour patterns are used to investigate the structure features of crystals of hexagonal selenium and tellurium grown in thin amorphous condensates of Se, SeTe, CuTe. The results are compared with microinterferometry data. Two bend effects are revealed: a hitherto unknown continuous bending, progressing with crystal growth of the lattice about the c-axis (360° rotation over a distance of 3 to 8 μm) and buckling of a thin-film crystal as a whole. The buckling is explained with the help of the following model: the build-up of the crystal lattice is accompanied by the formation of an abnormally large number of vacancy growth defects conditioned by crystallization from the amorphous state. As the excess vacancies emerge at the surface there arise compressive stresses developed by the amorphous film. [Russian Text Ignored].

Properties of piezoelectric selenium and selenium layers

Abstract Trigonal selenium is an interesting piezoelectric material since its electromechanical coupling factor is fairly high: K 2—10% for bulk waves and 1.5% for Rayleigh waves. The set of its elastic and piezoelectric constants is given. The propagation conditions of bulk waves (slowness surface) and surface waves are deduced from these constants. Experimental results referring to Rayleigh waves propagating in selenium crystals (they are difficult to grow) and in selenium layers grown on tellurium crystals are presented. These waves were launched by interdigital transducers.

Recovery behavior of tellurium irradiated with 20-MeV electrons and the influence of lattice defects on the transport properties

The reaction kinetics of the 50-K recovery stage of tellurium irradiated with 20-MeV electrons can be explained by correlated vacancy-interstitial annihilation. Moreover, the influence of the doping on the transport properties of irradiated tellurium crystals was investigated. It turned out that the assumption of a reduction of the dislocation scattering potential by vacancy trapping as proposed in previous papers is insufficient. The experimental findings are comprehensible if screening of the dislocations by free carriers is assumed to be the predominant mechanism. With this model the doping dependence of the mobility in unirradiated tellurium crystals can also be understood.

Effect of thermal gradients during Czochralski growth of tellurium crystals

Temperature profiles measured within a tellurium single crystal ingot during extension of its length by Czochralski growth have indicated internal temperature gradients which increase with decrease in the background temperature of the furnace tube. The magnitude of the axial gradients was accounted for by theoretical heat flow considerations but the radial gradients were larger than expected. Transport measurements at 77 K on samples cut from Czochralski-grown ingots showed a decrease of Hall mobility and of apparent extrinsic hole concentration with decrease of background temperature and hence with increase of maximum temperature gradient within the ingot. Subsequent annealing of samples raised the Hall mobility by a factor of two and the transverse magnetoresistance by a smaller amount. It is believed that carrier scattering centers are thus created in temperature gradients, which are always present during Czochralski growth, and that these defects can be removed by prolonged annealing.

A monochromatic and frequency stabilized cw source in the 5 μm region obtained by doubling the frequencies of a cw laser in tellurium

In this paper we describe the construction of a monochromatic and frequency stabilized continuous wave (cw) source in the 5 μm region. It is built up by a cw single line, single-mode frequency and amplitude stabilized CO2 laser. This primary CO2 laser source is then frequency-doubled in a tellurium crystal using second harmonic generation (SHG). The obtained emission is monochromatic (half-width 50 kHz). The frequency can be varied discreetly from 4.6 μm to 5.5 μ depending on the CO2 laser line chosen.

ChemInform Abstract: CRYSTAL AND MOLECULAR STRUCTURES OF THE (4‐ALKOXYPHENYL)TELLURIUM(IV) TRIHALIDES: (4‐ETOPH)TECL3, (4‐ETOPH)TEBR3, AND (4‐MEOPH)TEI3

Chemischer InformationsdienstVolume 11, Issue 48 Physical Organic Chemistry ChemInform Abstract: CRYSTAL AND MOLECULAR STRUCTURES OF THE (4-ALKOXYPHENYL)TELLURIUM(IV) TRIHALIDES: (4-ETOPH)TECL3, (4-ETOPH)TEBR3, AND (4-MEOPH)TEI3 P. H. BIRD, P. H. BIRDSearch for more papers by this authorV. KUMAR, V. KUMARSearch for more papers by this authorB. C. PANT, B. C. PANTSearch for more papers by this author P. H. BIRD, P. H. BIRDSearch for more papers by this authorV. KUMAR, V. KUMARSearch for more papers by this authorB. C. PANT, B. C. PANTSearch for more papers by this author First published: December 2, 1980 https://doi.org/10.1002/chin.198048065AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue48December 2, 1980 RelatedInformation