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[en] The temperature dependence of dc conductivity of Se_85-xTe₁₅Ge_x (x=0, 2, 6, 10, 15) chalcogenide glasses in the temperature range 273-333 K, has been reported. The dc conductivity varies exponentially with temperature for all compositions. The log σ_dc versus 1000/T plots are almost straight lines in whole studied temperature range indicating a singly activated phenomenon with single activation energy. Meyer-Neldel rule between pre-exponential factor and activation energy has been observed. Meyer-Neldel characteristic energy (E_MN) and σ₀₀ come out to be 40.67 meV and 3.78*10^-6 S cm^-1, respectively.Both values lie in the range predicted by Shimakawa and Abdul-Waheb for chalcogenide glasses. (author)

[en] Photoconductive properties such as dark conductivity, steady state and transient photoconductivity of a-Se_90-xTe₁₀Zn_x thin films, prepared by thermal vacuum evaporation technique have been studied in temperature range 312-380 K. Analysis of data shows that activation energy of dark current is greater as compared to activation energy of photo current. Activation energy decreases with increase in Zn concentration which may be due to increase in defect density of states. Analysis of intensity dependent photoconductivity shows that bimolecular recombination is predominant. Photosensitivity is found to be maximum for Se₈₈Te₁₀Zn₂ composition after that it decreases with increase in Zn concentration. Carrier lifetime decreases with increase in Zn concentration which also confirms that density of defect states increases. Transient photoconductivity shows that the carrier lifetime decreases with increase in Zn concentration. This decrease is due to transition trapping process. (author)

[en] Thin films of Se₈₅Te₁₀ X₅ (=Sn, In) were synthesized by the thermal evaporation technique. Both Ac and dielectric measurements were carried out in the frequency range (102-105 Hz) and the temperature range (303-333 K). The result of ac conductivity was found to follow the power law: (ac(ω)=A ωs with s<1) which is interpreted with the correlated barrier hopping model (CBH). The Ac conductivity exhibited a thermally activated behavior with an activation energy reduces with temperature. Both the dielectric constant ε1 (ω) and the dielectric loss (ε2(ω)) reduce with the frequency and rise with raising temperature over the examined ranges. Some parameters as Maximum barrier height WM, hopping energy WH, the localized state density NE(f) and relaxation time τ are estimated and their change with Sn/In addition is discussed. Sn addition improves the conductivity of Se-Te than In addition. (author)

[en] The dielectric properties and thermally assisted conduction are the two essential phenomena which determine the suitability of prepared chalcogenide glasses for specific device applications. Chalcogenide glassy alloy of a-Ge_10−xSe₆₀Te₃₀Sb_x (0 ≤ x≤6) was prepared by melt quench technique. Dielectric analysis and mechanism of ac conduction have been studied for the novel multicomponent chalcogenide glasses at frequency and temperature range (100 Hz–1 MHz) and (303–328 K) respectively. It has been clearly observed that the value of both dielectric constant (ε1) and dielectric loss (ε2) decreases with increasing frequency and increases with increasing temperatures. The variation of dielectric constant with frequency and temperature was described by orientational polarization. The change in dielectric loss with frequency and temperature was interpreted by Guintini relation. The ac conductivity follows the universal power law (Aωs) with frequency where the frequency exponent s ≤ 1 and it reduces with increase of temperature which confirms that the CBH model is best suited to describe the ac conductivity in the prepared glassy alloys. The change in dielectric constant, dielectric loss and a.c. conductivity with Sb doping was also examined.

[en] Short-wavelength infrared photo-sensing materials are dominated by germanium, indium gallium arsenide, indium antimonide, and mercury cadmium telluride. However, the complex fabrication process and high production cost hinder their widespread applications. Recently, Te${}_x$Se${}_{1-<!--\; ???\; -->x}$ has shown great potential for infrared photodetection, but Te${}_x$Se${}_{1-<!--\; ???\; -->x}$-based devices are still suffering from extremely high dark current and poor device performance. In this work, high-quality Te${}_x$Se${}_{1-<!--\; ???\; -->x}$ films are fabricated by thermal evaporation and low-temperature annealing. The optoelectronic properties of the Te${}_x$Se${}_{1-<!--\; ???\; -->x}$ thin films are systematically investigated and optimized. The absorption spectrum is carefully tuned to cover the broad range from 300 to 1600 nm by modulating the ratio of Te and Se. Photodiodes based on the optimized Te${}_x$Se${}_{1-<!--\; ???\; -->x}$ thin films are also fabricated, and achieve high responsivity, reduced dark and low noise current density, and a fast response time of <850 ns. Then, prototypical devices based on Te${}_{0.65}$Se${}_{0.35}$ thin films are demonstrated for optical communications, indicating the great potential for next-generation, low-cost short-wavelength infrared photodetection. (© 2023 Wiley‐VCH GmbH)

[en] Using the capabilities of the CRYSTAL14 code, the parameters of an equilibrium crystal lattice are obtained and the electronic and vibrational structures of a new chalcopyrite-like Zn₂SeTe crystal are studied. The energy band structure, long-wave vibrational frequencies at the point Г, and elastic moduli are calculated. The dependence of the contributions from the vibrations of individual atoms to the vibrational modes of a crystal caused by filling the cationic or anionic sublattices in the chalcopyrite structure is established.

[en] The 'selenium-tellurium' alloy was developed by vacuum distillation and zone purification methods. This alloy may be used for restoration of photoreceptor properties in photocopying cylinders. The obtained results permitted to evaluate the activation process energy and other parameters

[en] The data on crystallization of chalcogenide glasses in the systems of As-Se-Te, Ge-Se-Te, etc. are reviewed. The available data on the effect of composition and degree of purity of glasses on their stability to crystallization are considered. The stability to crystallization is compared on the basis of known criteria: the critical cooling rate, the Tc-Tg interval between the values for temperature of crystallization Tc and of glass-formation Tg determined by differential thermal analysis

[en] In this study, amorphous Bi_x(Se₈₀Te₂₀)_100-x glasses with (0 ≤ x ≤ 12) were prepared by the usual melt quench technique. Thin films of these glasses were deposited onto glass substrates by using thermal evaporation method. The amorphous nature of the as-prepared films was confirmed by X-ray diffraction. Structural investigations were performed using X-ray energy-dispersive spectroscopy, X-ray diffraction and high-resolution transmission electron microscopy. The transmission spectra of these films were measured at normal incidence in the wavelength range 400-2500 nm. Swanepoel's analysis of the maxima and minima of the interference fringes was used to determine the film thickness, the complex index of refraction and the extinction coefficient with high accuracy. The dispersion of the refractive index was well discussed in terms of the single oscillator model (Wemple and DiDomenico). It was found that increasing Bi content led to the increase in refractive index and the extinction coefficient of the Bi_x(Se₈₀Te₂₀)_100-x films, while the optical band gap decreased. The mechanism of the optical absorption in Bi_x(Se₈₀Te₂₀)_100-x films obeyed the allowed indirect optical transition. The decrease in optical gap with increasing Bi content was discussed in terms of the chemical bond approach (author)