V. F. Kozlovskii

Synthesis and optical properties of quasi-2D CdSxSe1 − x nanoparticles

Colloidal 2D CdSxSe1 − x nanoparticles have been synthesized by a solution method in octadecene using oleic acid as a stabilizer. Growth of quasi-2D nanoparticles has been promoted by the presence of cadmium acetate in the reaction mixture. The resulting nanoparticles are platelets with lateral sizes 20–30 nm. The absorption and luminescence spectra of these nanoparticles show narrow bands of lh-e and hh-e exciton transitions corresponding to 2D systems. The spectral position of the lowest energy hh-e transition monotonically changes within 382–461 nm with a change in the composition of nanoparticles. The observed absorption bands are broader than those for the individual CdSe and CdS nanoparticles. The suggested method makes it possible to vary the exciton band position for quasi-2D nanoparticles by changing their composition.

Pulsed laser deposition of conductive indium tin oxide thin films

Thin indium tin oxide (ITO) films have been grown on quartz glass substrates by pulsed laser deposition. The influence of ablation target composition and deposition conditions on the growth rate, optical transmission spectra, and carrier mobility and concentration of the films has been examined. The average surface roughness of the ITO films grown at substrate temperatures above 300°C is 2 nm. The films grown at an oxygen partial pressure of 5 mTorr using ablation targets with Sn/(In + Sn) = 5% possess high transmission (85-95%) in the visible range and low resistivity (1.8 × 10−4 Ω cm).

SnO2(Au0, CoII, III) nanocomposites: A synergistic effect of the modifiers in CO detection

Nanocrystalline SnO2 has been synthesized and its surface has been modified with Au0 and Co(II, III). The distribution of the modifiers over the nanocomposites has been studied by X-ray diffraction, inductively coupled plasma mass spectrometry, and transmission electron microscopy. The effect of the modifiers on the hydrogen reduction of nanocrystalline SnO2 has been assessed. The CO sensing properties of the synthesized materials (10 ppm CO in air) have been studied in situ by electrical conductance measurements. The addition of both Au0 and Co(II, III) allows the working temperature of the SnO2-based semiconductor sensor to be lowered to 215°C.

Effect of heterovalent substitution on the electrical and optical properties of ZnO(M) thin films (M = Ga, In)

Films of undoped ZnO and zinc oxide doped with gallium and indium (ZnO(Ga) and ZnO(In)) have been prepared by the spin-coating method with the subsequent annealing at 500°C. Phase composition, microstructure, conductivity, and optical properties of the films have been investigated depending on the content of gallium and indium in them.

Effect of Ga and in doping on acid centers and oxygen chemisorption on the surface of nanocrystalline ZnO

Nanocrystalline gallium- and indium-doped zinc oxide samples have been prepared through coprecipitation from aqueous solutions. Acid centers on the surface of the materials have been investigated using temperature-programmed desorption and IR spectroscopy. The results demonstrate that, with increasing dopant concentration, the density of OH groups on the surface of ZnO〈Ga〉 and ZnO〈In〉 increases and the contribution of cation centers to surface acidity decreases. The interaction of the material with oxygen has been studied using in situ electrical conductivity measurements. Doping of zinc oxide with gallium or indium has been shown to increase the percentage of molecular chemisorbed oxygen species on the surface of the material.

Transport properties of thin SnO 2 〈Sb〉 films grown by pulsed laser deposition

Thin SnO2 films grown by pulsed laser deposition have been characterized by X-ray diffraction, optical spectroscopy, and scanning electron microscopy. The carrier mobility and concentration in the films have been determined as functions of target composition (0–8 at % Sb) using Hall effect measurements, and the resistivity of the films has been measured by a four-probe technique. The lowest resistivity (ρ = 2 × 10−3 Ω cm) and the highest transmission (≃ 85%) of the films in the spectral range 400-800 nm have been obtained at a target composition Sb/(Sn + Sb) = 2 at %. The observed variation in the resistivity of the films is determined by changes in carrier concentration to a greater extent than by changes in carrier mobility. X-ray photoelectron spectroscopy results demonstrate that the predominant charge state of the antimony in the films is Sb5+.

Luminescent properties of Cd-In-Te solid solutions

The composition dependences of the unit-cell parameter for CdTe-based solid solutions in the CdTe-InTe and CdTe-In4Te3 joins have been used to determine the limits of the solid solutions. Magnetic susceptibility data and the measured and X-ray densities of the solid solutions suggest that CdTe doped with In2Te2 or In4Te3 contains In+ and In3+ on the cation site. The cathodoluminescence spectra of CdTe doped with In2Te2, In4Te3, and In2Te3 have been measured, and the effect of mixed heterovalent substitution (In+ and In3+) on the luminescence behavior of CdTe has been analyzed.

Controlling the phase composition of cadmium sulfide films during pulsed laser deposition

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.

Synthesis, structure, and luminescence properties of Cd1–x Mg x Te (0 < x < 0.20) solid solutions

We have synthesized CdTe–MgTe samples in the composition range 0–30 mol % MgTe. The composition dependence of the unit-cell parameter of the Cd1–xMxTe solid solutions has been obtained for the first time. The lattice parameter of cadmium telluride (sphalerite structure) has been shown to decrease almost linearly in the range 0 ≤ x ≤ 0.20. The 78-K cathodoluminescence spectra of the Cd1–xMgxTe (0 < x ≤ 0.15) solid solutions heat-treated under vacuum in order to remove the excess tellurium contain strong lines in the edge emission region, due to a transition from the conduction band to a shallow acceptor level.

Effect of cadmium chloride on the photosensitivity of Cd1–xMgxTe (0 ⩽ x < 0.10) films grown in a quasi-closed system

Films of Cd1–xMgxTe solid solutions have been grown by thermal evaporation of powders of CdTe-based MgTe–CdTe solid solutions in a quasi-closed system. The magnesium content of the films has been found to be lower than that of the source material used for film growth. It has been shown that the photocurrent amplitude in the Cd1–xMgxTe films as a function of incorporated CdCl2 concentration has a maximum at a particular cadmium chloride concentration, which is due to the doping of the solid solutions with chloride ions. The cadmium chloride-activated Cd1–xMgxTe films are n-type.