V. F. Markov

Nucleation and mechanism of metal sulfide film growth using deposition by thiocarbamide

The mechanism of hydrolytic decomposition of thiocarbamide upon the interaction with metal salts with deposition of thin films of sulfide was proposed. The kinetic studies of the transformation of metal salt into sulfide and IR spectroscopy confirmed that one of the hydrolysis products of thiocarbamide was cyanamide. The concept about the activation of thiocarbamide decomposition was extended due to the nucleophilic addition of anions to form an intermediate reaction complex thiocarbamide—metal ion—nucleophile. The activation weakens in the order OH− > CH3COO− > Cl− > Br− > I−. The presence and active role of colloidal components of reaction mixtures in the nucleation and formation of films of metal sulfides by chemical bath synthesis were established by spectrophotometric and kinetic measurements. It was concluded that from the viewpoint of fractal formalism metal sulfide films are formed in chemical bath deposition via the mechanism of cluster—cluster aggregation in the form of consecutive evolution of structural levels. A complex scheme of the mechanism of chemical bath deposition of metal sulfides by thiocarbamide was proposed. The results of studies of their phase composition, microstructure, and properties are presented.

Synthesis of films of solid solutions CdxPb1 − xS by the method of ion-exchange substitution

The possibility of obtaining films of substitutional solid solutions in a sulfide system via ionic exchange at the interface between the CdS film and the aqueous solution of a lead salt has been shown. The composition, structure, and morphology of freshly deposited films of CdS, PbS, and CdS layers held for 60–540 min at 353–368 K in an aqueous solution of lead acetate have been studied. It has been established by the methods of Raman spectroscopy (RS) and glancing-angle X-ray diffraction (GAXRD) that, due to ion-exchange processes, the formation of supersaturated substitutional solid solutions CdxPb1 − xS (x ≤ 0.31) occurs in the film, the cadmium content in which decreases gradually over the film thickness.

Effect of an iodine-containing additive on the composition, structure, and morphology of chemically deposited lead selenide films

The effect of an ammonium iodide additive on the elemental and phase compositions, structural parameters, and surface morphology of lead selenide films synthesized by chemical deposition from aqueous solutions has been studied using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray analysis. It has been established that the obtained PbSe films have a multiphase structure. The iodine content of the films is directly proportional to the NH4I concentration in the reaction mixture and increases linearly with an increase in this concentration to 0.25 mol/L. No individual iodine-containing phases have been detected in the film structure. However, the introduction of iodine leads to an increase in the PbSe phase lattice parameter from ∼6.11 to ∼6.16 Å and to a decrease in the crystal grain size to ∼ 20 nm. It has been found that there is a correlation between the grain size, lattice parameter, and ammonium iodide concentration in the reaction mixture, which can be explained by changes in the film growth mechanism at the initial growth steps.

Diagrams of the formation of In 2 S 3 and In 2 Se 3 films on vitroceramic upon precipitation, according to potentiometric titration

Boundary conditions and ranges of the formation of indium(III) sulfide and selenide upon precipitation by thiocarbamide and selenocarbamide are determined. Potentiometric titration of indium chloride (InCl3) in the concentration range of 0.0001 to 0.100 mol/L by a solution of sodium hydroxide is performed. It is found that the following pH ranges are optimal for In2S3 and In2Se3 film precipitation: from 3.0 to 4.5 and from 9.0 to 14.0. Indium selenide layers 100 to 300 nm thick are prepared on vitroceramic by hydrochemcial precipitation.

Nanostructured copper(I) sulfide films: Synthesis, composition, morphology, and structure

Possibility of forming the solid phase of copper(I) and (II) sulfides in ammonia and acetate solutions at pH values exceeding 10 was demonstrated by calculation with the use of thiocarbamide. Mirror-like nanocrystalline layers of exclusively monovalent copper sulfide Cu2S of stoichiometric composition with thicknesses of up to 110 ± 10 nm were formed on glass-ceramic substrates at 298–343 K via chemical deposition from solutions of both kinds due to the reducing properties of thiocarbamide. The films produced from the acetate system are more uniform and are constituted by globules (~10 nm) forming agglomerates up to 80–150 nm in diameter. According to X-ray diffraction data, they are crystallized in the chalcocite structure (space group P21/c) with crystal lattice constants a = 1.5307(5) Å, b = 1.1908(5) Å, c = 1.3485(6) Å, and β = 116.60(1)°.

Influence of the ligand nature on the boundary conditions of the formation and the morphology of nanocrystalline cadmium sulfide films

Ionic equilibriums in the Cd2+–L–N2H4CS (L = NH3, H2NCH2CH2NH2, C6H5O73–, NH3 + C6H5O73–) systems have been analyzed. The ranges and boundary conditions of the formation of cadmium sulfide CdS and the accompanying Сd(OH)2 and СdCN2 impurity phases have been determined. 100–200 nm thick nanocrystalline cadmium sulfide films constituted by 10–30-nm particles arranged into globules with diameter of 400–700 nm have been synthesized. The effects of the nature and strength of the complexing agent on the microstructure and morphology of the resultant CdS layers have been demonstrated using scanning electron microscopy.

Conditions of hydrochemical synthesis, composition, and structure of tellurium films

Conditions of the hydrochemical synthesis of thin tellurium fi lms by reduction of an aqueous solution of tellurous acid with hydrazine were determined. The redox potentials of tellurous acid and hydrazine and their difference in relation to pH of the medium and concentration of tellurite ions were calculated. The kinetics of tellurium layer growth on glass-ceramic substrates and the structure, composition, and morphology of the layers were studied.

Kinetics of hydrochemical deposition of PbSe films in the presence of ascorbic acid

The boundary conditions of the formation of PbSe and concomitant impurity phases, Pb(OH)2 and PbCN2, were determined by calculation of the ionic equilibria in the Pb2+–Na3C5Н6О7–CH4N2Se system. Complex kinetic studies of the PbSe deposition from an ammonia–citrate mixture containing ascorbic acid as antioxidant for selenourea were performed. PbSe films 250 to 425 nm thick were synthesized by the hydrochemical method based on the results obtained. The absence of impurities in the deposited samples was confirmed by X-ray diffraction analysis.

Assessment of the ability of metal chalcogenides to enter into ion-exchange reactions in aqueous solutions

A versatile computational method for assessing the ability of metal chalcogenides to enter into ion-exchange reactions in aqueous solutions is proposed for the first time. Taking into account the ligand environment allows one to a priori predict the qualitative and quantitative composition of aqueous solutions favorable to mutual ion-exchange transformations of metal chalcogenides aimed at performing targeted synthesis of substitutional solid solutions and composite structures based on the title compounds.

Structure and composition of chemically deposited In2S3 thin films

Nanostructured thin indium(III) sulfide thin films 285–756 nm thick are obtained via chemical deposition from aqueous solutions containing indium chloride, thioacetamide, tartaric acid, and hydroxylamine hydrochloride at temperatures of 343–368 K. Oxygen- and carbon-containing impurities, which are not observed in the film bulk (at a depth of 12 nm), are detected in the surface layers of the films. When the synthesis temperature increases, the layer morphology changes substantially and the crystallite size increases from 70 to 150 nm. Upon annealing at a temperature of 573 K, crystallite aggregates are fused and In2S3 films are enriched with 6 to 10 at % of oxygen.