Vol 53, No 11 (2017)

We have studied the chemical dissolution of InAs, InSb, GaAs, and GaSb crystals in (NH₄)₂Cr₂O₇–HBr–C₆H₈O₇ solutions. The dissolution rate of the crystals has been measured as a function of etchant composition, and the kinetics of the chemical interaction of the semiconductors with solutions have been investigated in detail. The dissolution rate has been shown to be diffusion-limited. Citric acid helps to reduce the etch rate and improves the polishing performance of the etching solutions.

Thin cadmium sulfide films grown by pulsed laser deposition on crystalline and amorphous substrates have been shown to consist of a mixture of a cubic (sphalerite structure) and a hexagonal (wurtzite structure) phase. We have demonstrated the possibility of controlling the percentages of the hexagonal and cubic phases in cadmium sulfide films by varying pulsed laser deposition parameters. Varying the deposition parameters allows one to control the optical and structural parameters and surface morphology of thin cadmium sulfide films.

Density functional theory calculations have been used to study the electronic structure of Mn-doped, Ni-doped, and Mn/Ni-codoped InSb and GaAs semiconductors. The ferromagnetic transition energy has been calculated using a multiscale method in which exchange interaction is calculated by the Hartree–Fock exact atomic method and is then included as a Hubbard parameter in calculation of the electronic structure of the material. The present calculation results demonstrate that, in all cases, there is hybridization of the impurity d states with the valence band of the host semiconductor. The contributions of the Ni and Mn dopants are approximately additive.

Cd_1–xFe_xCr₂S₄ (x = 0.5–0.8) spinel solid solutions have been synthesized and their magnetic properties have been measured using a Quantum Design PMS-9 instrument at temperatures from 5 to 300 K in a static (7960 A/m) and an ac (100, 1000, and 10000 Hz) magnetic field (79.6 A/m peak) at an external field H = 0. At low temperatures, all of the solid solutions have extended ranges where their dynamic magnetic susceptibility around their ferrimagnetic transition is frequency-dependent. The obtained results are discussed in terms of models that take into account the instability of the long-range magnetic order in the endmembers of the solid solution system: FeCr₂S₄ and CdCr₂S₄.

A process has been developed for the liquid phase epitaxy of mesa stripe buried crescent InP/InGaAsP/InP heterostructures with a p–n–p–n/ZnSe leakage current-blocking structure. The salient feature of the process is a discontinuous mesa stripe which alternates with the structure of blocking layers. This technology allows one to fabricate linear edge-emitting diodes, mounted with the mesa stripe down or up, with an emission wavelength λ = 1.3–1.5 μm, high reproducibility, the possibility of coupling more than 50 μW of optical power into single-mode fiber at a current of 100 mA, an emission bandwidth of about 60 nm, and essentially negligible Fabry–Perot modulation.

Titania coatings containing crystalline titania particles 10 to 20 and 100 to 300 nm in size or a combination of such particles have been produced by a sol–gel process on the surface of aluminum substrates. According to X-ray diffraction characterization results, the coatings consist predominantly of crystalline titania in the form of anatase. The decomposition of an organic test dye (Rhodamine B) in an aqueous solution under irradiation with UV light demonstrates that the highest photocatalytic activity is offered by the coatings containing both nanometer- and submicron-sized titania particles.

A stoichiometric lithium niobate crystal (LiNbO_{3 st}) and congruent lithium niobate crystals grown from a charge prepared using cyclohexanone as an extractant (LiNbO_{3 cong}(CHN)) and a charge prepared using cyclohexanone and carboxylic acid dimethylamides as extractants (LiNbO_{3 cong}(CHN + A)) have been characterized by photoinduced light scattering and laser conoscopy. The results demonstrate that the LiNbO_{3 cong}(CHN + A) crystals are rather homogeneous along their growth direction and possess good optical properties, similar to those of the LiNbO_{3 cong}(CHN) crystal. At the same time, the LiNbO_{3 cong}(CHN + A) crystal offers significantly better electro-optical properties (r_e = 29.3 pm/V).

The thermal behavior of (TeO₂)_n(MoO₃)_1–n (n = 0.75, 0.85, 0.90) tellurite glasses has been studied by differential scanning calorimetry in the range from T = 300 to T = 850 K and heat capacity has been measured in the temperature range. The thermodynamic characteristics of the devitrification process and glassy state have been determined. The experimental data obtained have been used to evaluate the standard thermodynamic functions of the system in glassy and supercooled liquid states: heat capacity C_p°(T), enthalpy H°(T)–H°(320), entropy S°(T)–S°(320), and Gibbs function G°(T)–G°(320) in the temperature range 320–630 K. The composition dependences of the glass transition temperature and thermodynamic functions for the glasses have been obtained. The thermal and thermodynamic properties of the tellurite glasses have been compared to those of previously studied (TeO₂)_n(WO₃)_1–n and (TeO₂)_n(ZnO)_1–n glasses.