The dissertation is dedicated to the development of technological regimes for the deposition of thin films of CuO, as well as carbon and carbon-containing materials with specified and reproducible electrical and optical properties. It also demonstrates the practical application of these materials in modern heterostructural electronic and optoelectronic devices.
The introduction justifies the choice of the topic and the relevance of the work, formulates the aim, main tasks, object and subject of research, highlights the scientific novelty and practical value of the obtained results, provides information about the author's contribution, the work's approval, its structure, and scope.
The first chapter of the dissertation presents a literature review, indicating significant global interest in the research of copper oxide thin films and graphite, as well as the development of high-efficiency optoelectronic devices based on them.
In the second chapter of the dissertation CuO thin films were produced by the method of reactive magnetron sputtering at direct current in a universal vacuum system Leybold-Heraeus L560 on glass substrates, the temperature of which was: 300 K and 523 K. The structural, electrical and optical properties for the obtained samples of CuO thin films were studied, namely: elemental composition, distribution of elements on the surface, which are part of these films, grain size, activation energy, optical band gap, refractive index, analysis of curves of transmission and reflection spectra for CuO thin films deposited on glass substrates. The elemental composition of the thin films and the surface morphology were performed using a scanning electron microscope (MIRA3 FEG, Tescan) equipped with a reflected electron detector (BSE) and an energy-dispersed X-ray detector (EDX). It was found that the grain size for films obtained at a lower substrate temperature D is 16 nm, and for films obtained at a higher temperature – D 26 nm. On the diffractograms of CuO thin films, a higher peak intensity is observed for thin films obtained at higher CuO no. 2 substrate temperatures, which may be due to better structural perfection of thin films and larger grain size.From the study of electrical properties, it was found that the temperature dependences of the electrical resistance for CuO thin films have a semiconductor character, ie the resistance decreases with increasing T. The surface resistance of the films was measured by the four-probe method: no. 1 – ρ = 18,69 kΩ/•, sample no. 2 – ρ = 5,96 kΩ/•.Based on independent measurements of the reflection and transmission coefficients, the optical band gap was determined for the two samples by extrapolation of the rectilinear section of the curve (αhν)2 = f (hv) to the hv axis. For the sample CuO №1 Egop = 1.62 eV; for the sample CuO no. 2 Egop = 1.65 eV. For CuO no. 2 thin films, the envelope method was also used to determine the basic optical coefficients Egop = 1.72 eV, and the obtained Egop values determined by the two methods correlate well with each other.
Thin films (300 nm thick) of CuO of p-type conductivity were precipitated using spray pyrolysis method from 0.2 M of aqueous CuCl2 ∙ 2H2O salt solution on preheated (up to 350 °C) glass and sitall substrates. The structure and electrical and optical properties of the films are analyzed. The grain size of CuO thin films (24 nm) was calculated using the XRD analysis. The activation energy equals to Ea = 0.27 eV, which may indicate that the conduction is due to the transition of charge carriers from the valence band to working acceptor level. From the spectral dependence (αhν)2 = f(hν) of CuO thin films, the band gap width Eg = 1.46 eV was determined.
Investigated the potential of copper oxide (CuO) thin films as active layers in thin-film solar cells with a Glass/ITO/Graphite/CuO/Ni structure. Furthermore, the generation rate of charge carriers was derived by modelling the optical field distribution using a transfer metric simulation. Theoretical thresholds for photovoltaic device efficiency were determined for varying active layer thicknesses by employing a normalized light intensity equivalent to that of the AM1.5 spectrum. The current-voltage characteristics are modeled by semi-empirical methods, which illustrate that the photovoltaic conversion efficiency depends on the thickness of the active layer. The highest performance of the simulated structure of the solar cell was 25.2%, which was obtained for the 500 nm CuO films.
In the third chapter of the dissertation, the research results results of studying the structural, optical and electrical properties of thin films of graphite depending on the hardness of the rods (2H, H, HB, B and 2B) obtained by the "Pencil-on-semiconductor" method. Such studies are of great importance for the further development of highly efficient devices based on heterojunctions for electronics and optoelectronics. Typical images of the surface formed by reflected electrons.
