We demonstrate how the formation of octahedral microcrystals of arsenic oxide As2O3 in the form of arsenolite with a size of 200 nm to 10 μm can be initiated by the electrochemical etching method with simultaneous deposition on the surface of substrates with n-GaAs (111). Crystallites were formed on a previously synthesized porous layer of GaAs. To explain the behavior of formation on the surface of the monocrystalline GaAs porous layer and As2O3 crystallites in the electrochemical reaction, we propose a qualitative model based on the decomposition of binary semiconductors in contact with electrolytes. Under this model, the crystallization of precipitated oxides occurs as a result of the transfer of ions to the crystal surface as a result of the electrolysis process. The formation of the composite structure takes place on the surface of the semiconductor and is characterized by the minimization of elastic energy. XRD analysis showed the formation of a complex compound of As2O3 and As0.172Sb0.570O1.113. The appearance of antimony is explained in terms of the formation of new centers when the As atom is replaced by an Sb doping atom in the crystal. Directed controlled oxidation technologies make it possible to synthesize a reliable passivating layer consisting of one type of oxide, namely As2O3 in the cubic phase of arsenolite. In addition, such structures can be used in photonics devices and as photocatalysts.

Purpose: f this paper is to is to establish the patterns of oxide formation on the surface of indium phosphide during electrochemical etching of mono-InP. Design/methodology/approach: A porous surface was formed with the anode electrolytic etching. Morphology of the surface was studied with the help of scanning electron microscope JSM-6490. The analysis of chemical composition of porous surface of samples was also performed. Findings: It was shown that during the electrochemical etching of indium phosphide, oxide films and crystallites form on the surface. It has been established that crystalline oxides are formed mainly on the surface of n-type indium phosphide. Continuous oxide films are predominantly formed on the surface of p-InP. Research limitations/implications: The research was carried out for indium phosphide samples synthesized in the solution of hydrofluoric acid, though, carrying out of similar experiments for crystalline oxides on the surface of porous indium phosphide obtained in other conditions, is necessary. Practical implications: The study of oxide crystals on the surface of porous indium phosphide has great practical importance since it is the reproducibility of experimental results that is the main problem of modern materials science, the more nanoengineering. Oxides can significantly affect the properties of materials. On the one hand, oxides significantly affect the recombination properties of materials, this can impair the operation of semiconductor devices. On the other hand, oxide films can serve as a passivating coating for the surface of a porous semiconductor. Such an oxide property will be useful for the practical application of nanostructured indium phosphide. Therefore, questions of the conditions for the formation of semiconductor intrinsic oxides, their structure, and chemical composition, and also the effect of oxides on the physical and technical characteristics of materials are important. Originality/value: The patterns of oxide formation on the surface of indium phosphide during electrochemical etching are investigated in this work. It is shown for the first time that the structure of an oxide depends on the orientation of the surface of the semiconductor. It was shown that continuous oxide films are formed on the surface of p-InP, and oxide crystalline clusters are formed on the surface of n-InP.

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CdxTeyOz/CdS/ZnO heterostructures were obtained by the SILAR method using ionic electrolytes. A CdS film was formed as a buffer layer for better adhesion of the cadmium-tellurium oxides to the substrate surface. In turn, the ZnO substrate was previously prepared by electrochemical etching to form a rough textured surface. In addition, an annealing mode was used in an oxygen stream to complete the oxidation process of the heterostructure surface. The resulting nanocomposite was investigated using RAMAN, XRD, SEM, and EDX methods. We assume that the oxides CdO and TeO4 initially form on the surface and later evolve into TeO2 and TeO3 when saturated with oxygen. These oxides, in turn, are the components of the ternary oxides CdTeO3 and CdTe3O8. It should be noted that this mechanism has not been fully studied and requires further research. However, the results presented in this article make it possible to systematize the data and experimental observations regarding the formation of cadmium-tellurium films.

Purpose: The paper aims to determine the values of the main morphological characteristics of nanopatterns, which can be considered as the reference for use as surfaces of solar cells. Design/methodology/approach: The article uses an approach based on the definition of reference indicators of nanopatterns for solar cells by analysing the main parameters of solar cells and comparing them with the possible values of morphological parameters. Correlations of pore radius and visible wavelength, porosity and visible range, wavelength of de Broglie, nanopatterned layer thickness and charge carriers diffusion length, etc., are analysed. Compliance verification of morphological characteristics of nanopatterns with the specified criteria was performed on the example of porous silicon layers. Findings: The conducted research allowed to define the basic values of morphological parameters of porous nanopatterns, namely porousness, pore size (effective diameter), the thickness of the porous layer, and form factor. Reference ranges of morphological parameters of nanopatterns formed on the surface of semiconductors for applications in solar cells are established. Research limitations/implications: The article is devoted to the choice of optimal morphological characteristics of porous nanopatterns on the surface of semiconductors for solar cells. However, for solar cells, other types of nanopatterns can also be applied, for which it is also necessary to develop methods for selecting optimal parameters. Moreover, the prospect of research on this topic is to check the intrusion into a certain range of values of real nanopatterns formed on the surface of semiconductors. Practical implications: In the article the methodology allowing to choose optimal values of morphological parameters of nanopatterns for its application for solar cells is considered. Such studies are of great practical importance for the production of high-quality solar cells based on nanopatterned semiconductors. Originality/value: The article for the first time considers the choice of the nanopattern type and the ranges of morphological parameters in terms of quality assurance of the final product – the solar cell. It is determined that it is necessary to take into account such factors as porousness, pore size, thickness of the porous layer and roundness. A range of optimal values is selected for each of the indicators.