Vol 81, No 9 (2017)

The characteristic energy of distributions of Ag and Cu nanoclusters in LiF-based thin films is estimated from the slope of the I–V characteristic, built in double logarithmic coordinates logI = f (logU). It is shown that the energy states of small clusters lie above the bottom of the conduction band and form a potential barrier, while the energy states of large clusters lie below the bottom of the conduction band and form a potential well. The change in the positions of energy levels along with nanocluster size and the effect of quantum limitations imposed on the electrical and optical properties of the system are confirmed experimentally.

The optical spectra and electric conductivity of LaF₃ crystals doped with 0.01, 0.1, and 0.3 mol % YbF₃, where Yb was partly or completely recharged to the divalent state, are studied. The long-wavelength absorption band of 370 nm is caused by electrons transitioning from state 4f¹⁴ to the level of anion vacancies. The remaining bands at 300–190 nm are caused by 4f¹⁴–5d¹4f¹³ transitions in Yb²⁺. The bulk electric conductivity and peaks of the dielectric losses of LaF₃–Yb²⁺ crystals are caused by Yb²⁺–anion vacancy dipoles. The activation energy of the reorientation of Yb dipoles is 0.58 eV. The optical and dielectric properties of Yb²⁺ centers are compared to those of Sm²⁺ and Eu²⁺ centers studied earlier in LaF₃ crystals.

The ground state of monovalent ions of transitional metals in alkaline-earth fluorides is localized in the conduction band. It is shown by the example of monovalent Co and Ni ions in CaF₂ and SrF₂ crystals that this is responsible for the unstable state of these ions in cubic environments. A stable state is achieved by the monovalent ions shifting to off-center positions.

Using the numerical method of finite elements, conjugate heat transfer is studied in different modes of heat transfer in a crystal–environment–growth chamber walls system geometrically similar to a simplified scheme of the thermal unit top in Czochralski process. Calculations are performed by varying the lengths of the seed crystals, along with the thermal conductivities of the crystal and rod. The Prandtl number is 0.68 (for argon), and the Grashof number is 16000.

The absorption spectra of radiation-colored CaF₂, SrF₂, and BaF₂ crystals activated by trivalent Pr, Sm, Нo, Er, Tm, and Yb (rare-earth, RE) ions are studied. It is shown that ionizing radiation reduces the impurity ions to the divalent state. The temperature resistance of divalent RE ions of radiation-colored CaF₂ crystals correlates with the chemical stability of the compounds with divalent RE ions. The photochromic centers are produced in CaF₂-Pr crystal colored by radiation at room temperature and heated to 200°C.

Natural diamonds are studied via confocal scanning fluorescent spectroscopy. Defects 523 and 794 nm have a number of similar features and are associated with one another. Features of their localization in the (111) planes of the individual growth pyramids testify to their postgrowth origin and are the result of plastic deformations. The structure of the defects presumably contains dislocations. The participation of other impurities in the structures of the defects is doubtful.

Results from studying quartzites of the Bural–Sardyk deposit in the quartz province adjacent to Lake Baikal are presented. These quartzites are a potential source of quartz raw material. The most promising quartzites of the deposit are briefly described. The effect heat treatment has on the depth of chemical enrichment is determined. The prospects of using quartzites in the production of quartz concentrate are examined.

IR and UV spectroscopy is used to study the properties of nanostructured aluminum nitride films obtained via reactive ion-plasma sputtering on GaAs substrates with different orientations. Nanostructured thin (100–200 nm) films of cubic aluminum nitride with optical bandgaps of ~5 eV and refractive indices varying from 1.6 to 4.0 in the wavelength range of ~250 nm are fabricated. Growth on a misoriented GaAs(100) substrate (4° with respect to the [110] plane) makes it possible to synthesize AlN films with smaller grains and higher refractive indices (n ~ 4). It is shown that misoriented GaAs substrates allow us to control the morphology, surface composition, and optical functional characteristics of AlN/GaAs heterophase systems.

The applicability of the spectrophotometric method for the quantitative determination of phenazepam using methyl red as an optical reference sample is demonstrated. The optical parameters of methyl red’s absorption bands and its optimum regions of absorption are confirmed, a scaling ratio is determined, and equations for the calibration curves are proposed.

The results from a theoretical study of the electron structure of an impurity rare-earth Sm²⁺ defect in a LaF₃ crystal are presented. The electron energy levels of the rare-earth impurity defect and the transitions between them are studied using the multiconfigurational CASSCF/CASPT2 method. The absorption spectrum obtained during the calculations is consistent with the experimental data. Based on our model, we can state definitively that a vacancy on an anion sublattice serves as a charge compensator for a divalent ion.

The joint effect of the impurity profile of a material and the thermal conditions of the formation of color centers upon irradiation in crystalline optical media is investigated. Special attention is given to additional gamma re-irradiation in thermally effective ranges for active centers, which establishes conditions for their preferential production.