We proposed a self-powered UV-vis-NIR Schottky junction photodiode based on a unique combination of radiation-hard functional materials: thin-film semi-metal Graphite and CdZnTe single-crystal compound semiconductor. The Graphite/CdZnTe Schottky junction photodiodes exhibit a maximum responsivity of 0.25 A W−1 and detectivity of 6.5 × 1011 Jones, close to the best heterojunction photodiodes based on CdZnTe solid solution. The devices are also characterized by short rise/fall times (1.2/7.2 µs) and a wide linear dynamic range (77 dB). The proposed photodiodes are promising for applications in space and terrestrial areas with high levels of ionizing radiation.
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.
The paper presents the 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 (BSE) were obtained using a scanning electron microscope and shown at three magnifications (100x, 500x and 1000x). Since the cores of the studied pencils consist of mixtures of clay and graphite, a more detailed analysis of the elements that make up the cores was conducted. EDS analysis showed that the main components of the studied rods are purified graphite powder, as well as O, Al and Si, which are part of kaolin whose formula is H4Al2Si2O9, or Al2O3 • 2SiO2 • 2H2O - the main component of ordinary clay. The elemental composition of the microvolume of the studied samples was also determined. Regardless of the error that occurs when determining the composition of C and O (~ 12%), it can be argued that there is still a regularity between the graphite content and the hardness of the pencil. That is, the higher the graphite content, the softer the rod. The thickness of the graphite films was measured using the MII-4 interferometer according to the standard method. The average thickness of all investigated films was ~ 150 nm since the thickness of the films obtained by this method is mainly determined by the roughness of the surface of the salt substrate. Drawn graphite films have a higher resistivity than bulk samples (pencil rods) from which they were made. The resistance of the films increases with an increase in the hardness of pencils, due to an increase in the number of clay impurities in graphite, which is a dielectric. It was found that an increase in stick hardness leads to an increase in transmission.
Thin films (300 nm thick) of CuO of p-type conductivity were precipitated using the 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 Ea = 0.27 eV, which may indicate that the conduction is due to the transition of charge carriers from the valence band to the 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. topics: CuO, spray pyrolysis, optical properties, thin films
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