Diana Junisbekova

This work presents a study of copper selenite nanocrystals, obtained for the first time by chemical deposition (template synthesis) in a SiO₂/Si track template, and investigates their properties. The obtained nanostructures were subjected to structural, optical, and electrical analysis. After deposition, X-ray diffraction (XRD) analysis confirmed the formation of the orthorhombic phase CuSeO₃. Subsequent annealing in a vacuum at 800 °C and 1000 °C led to successive phase transformations: to the monoclinic phase and, finally, to the triclinic polymorph of copper selenite. Photoluminescence (PL) analysis showed that the intensity and spectral position of the emission peaks vary depending on the crystal structure, which is associated with changes in defects and bandgap width as a result of heat treatment. Current–voltage characteristic (CVC) measurements showed that the phase composition significantly affects electrical conductivity. In particular, the transition to the triclinic phase after annealing at 1000 °C led to noticeable changes in optical and electrical properties compared to the initial material. Thus, a direct relationship has been established between heat treatment conditions, crystal structure, and functional properties of CuSeO₃-based materials, opening up possibilities for their application in photonics and electronics.

Model experiments were performed on the interaction of swift heavy 220 MeV Xe ions with MgAl₂O₄ spinel crystal with (100), (110), and (111) planes. A computational analysis of the energy parameters of Xe ions in MgAl₂O₄ single crystal was performed, and an estimate of the ion range in the near-surface layer (14 μm) was provided. Optical absorption spectrum was analyzed using polarized light and EPR spectroscopy of initial and irradiated crystals. It has been established that at a fluence of 10¹³ cm⁻² in a sample with an orientation plane (110), 35% more optically active F-type centers are formed. It has been shown that optically active centers V|_Al–O⁻ are observed in an unusual, polarized beam.

Metal-coated mesoporous PSi (mesoPSi) opens up disruptive perspectives for biosensing, which is primarily enabled by surface-enhanced Raman scattering (SERS). Although the unique performance of SERS-active substrates based on metal-coated mesoPSi has already been praised, influence of defects in silicon wafer on its morphology has not been revealed. Defects lead to formation of spiral regions in mesoPSi with varying porosity, which affects SERS activity of the overlying metallic nanostructures. It limits the reliability of SERS analysis. Here, we investigate repeatability of morphology and SERS activity of silver particles on mesoPSi as a function of defects in parent silicon, which are induced by irregular dopant levels. We propose an original corrosion approach that has not yet been applied to control the morphology of silicon nanostructures in general and mesoPSi in particular. By replacing silicon nanocrystallites with sacrificial copper nanoparticles, we were able to eliminate the surface irreproducibility of mesoPSi. The copper-corrosion-modified porous silicon surface was shown to be a suitable substrate for reliable SERS-active substrates. In more detail, SERS-active substrate based on mesoPSi without a defective surface layer allowed for a more than 40% increase in the SERS-active surface area with a signal deviation of only 10 % compared to that with a defective layer.

The regularities of chemical contact-exchange deposition of thin copper films on porous silicon are investigated. Aqueous and aqueous-alcoholic solutions of copper sulfate with hydrofluoric acid additives are used for copper deposition. The optimal ratio of solution component concentrations is determined, which allows controlling the kinetics of the deposition process and obtaining shiny copper films with good adhesion to the silicon substrate. It is established that copper is deposited on porous silicon in the form of a film consisting of micro- and nanometer-sized grains. The packing density and the size of copper grains are determined by both the deposition time and the pore diameter of porous silicon. It is shown that at a porosity of up to 10%, copper grains nucleate only on the vertices of silicon nanocrystallites of the porous silicon matrix. An increase in porosity leads to the simultaneous nucleation of copper grains on the inner surface of the pore channels and the vertices of silicon nanocrystallites. Reflection spectra of nanocomposite films were recorded. It was found that the maximum intensity of the absorption band, caused by surface plasmon resonance, is characteristic of a film deposited for 5 min. from an alcohol-containing solution on porous silicon, which was formed on the silicon wafer of n-type with resistivity 0.01 and orientation (111). Thus, by varying the pore sizes of the porous layer and the deposition conditions, it is possible to manufacture various types of thin-film nanocomposite structures from silicon and copper, promising for use as functional nanomaterials in electronics and photonics.

YAG (Y₃Al₅O₁₂) is one of the important optical materials. It is widely used in solid-state lasers, lighting devices as a white LED converter, and in scintillation technology.In this work, YAG (100) single crystals were irradiated with 230 MeV Xe ions to fluences of 6·10¹⁰–10¹³ ion/cm², which allows us to study the behavior of the material in hard radiation fields. The following research methods were used to analyze the irradiated YAG crystals: optical absorption spectroscopy and Raman spectroscopy.Analysis of the absorption spectra shows the formation of color centers in the irradiated YAG samples. The concentration of various types of point defects increases significantly with increasing fluence. The difference spectra reveal overlapping bands in the range of 4.1–5.2 eV, which correspond to different configurations of F₂ centers. With increasing fluence, the surface layer becomes amorphous, and the material is amorphized. High-energy modes of Raman spectra begin to expand already at a fluence of 10¹⁰ ion/cm². Considering the high degree of influence of Xe ions, it can be stated that starting from a fluence of 10¹² ion/cm², all cation-anion bonds are practically destroyed.

This work presents a study of the structural, optical and electrical characteristics of tin dioxide (SnO2) nanowires obtained by chemical deposition (CD) into SiO2/Si track templating (templating synthesis). Latent tracks in the SiO2 layer were created by irradiation with fast heavy ions (FHE) Xe at 200 MeV energy with fluence F = 108 cm-2 followed by etching in 4% aqueous hydrofluoric acid (HF) solution. The selected XO method is widely used for the deposition of semiconductor oxide nanowires in SiO2 nanopores. The CW method is cost-effective because it does not require any special equipment for the deposition of nanowires. To realize the deposition, a solution of metal coordination compound and reducing agent is used. To analyze the pore filling after CW process, the surface morphology of the samples was investigated using Zeiss Crossbeam 540 scanning microscope. The crystallographic structure of SnO2/SiO2/Si nanostructures with SnO2 nanopore filling was investigated by X-ray diffraction. X-ray diffraction analysis (XRD) is performed on a Rigaku SmartLab X-ray diffractometer. A SnO2-NP/SiO2/Si nanostructure with orthorhombic crystalline structure of SnO2 nanowires supplemented with metallic tin was obtained. The photoluminescence spectra were measured under excitation with 5.17 eV wavelength light using a CM2203 spectrofluorimeter. Gaussian decomposition of the photoluminescence spectra of SnO2-NP/SiO2/Si structures, showed that they have low intensity, which is mainly due to the presence of defects such as oxygen vacancies, interdomain tin or tin with damaged bonds. The electrical characterization study was carried out using a VersaStat 3 patentiostat. The WAC measurement of the nanowire obtained by chemical deposition showed that due to the presence of metallic tin, the conductivity is close to metallic.

In this study, chemical deposition was used to synthesize structures of Ga₂O₃ -NW/SiO₂/Si (NW—nanowire) at 348 K and SnO₂-NW/SiO₂/Si at 323 K in track templates SiO₂/Si (either n- or p-type). The resulting crystalline nanowires were δ-Ga₂O₃ and orthorhombic SnO₂. Computer modeling of the delta phase of gallium oxide yielded a lattice parameter of a = 9.287 Å, which closely matched the experimental range of 9.83–10.03 Å. The bandgap is indirect with an Eg = 5.5 eV. The photoluminescence spectra of both nanostructures exhibited a complex band when excited by light with λ = 5.16 eV, dominated by luminescence from vacancy-type defects. The current–voltage characteristics of δ-Ga₂O₃ NW/SiO₂/Si-p showed one-way conductivity. This structure could be advantageous in devices where a reverse current is undesirable. The p-n junction with a complex structure was formed. This junction consists of a polycrystalline nanowire base exhibiting n-type conductivity and a monocrystalline Si substrate with p-type conductivity. The I–V characteristics of SnO₂-NW/SiO₂/Si suggested near-metallic conductivity due to the presence of metallic tin.

This work presents a study of the structural, optical and electrical characteristics of tin dioxide (SnO2) nanowires obtained by chemical deposition (CD) into a SiO₂/Si track template (template synthesis). Latent tracks in the SiO₂ layer were created by irradiation with swift heavy ions (SHI) of Xe at an energy of 200 MeV with a fluence of Ф = 10⁸ cm⁻² and subsequent etching in a 4% aqueous solution of hydrofluoric acid (HF). The chosen CD method is widely used for the deposition of semiconductor oxide nanowires in SiO₂ nanopores. The CD method is cost-effective because it does not require special equipment for deposition of nanowires. To carry out deposition, a solution of a coordination compound of a metal and a reducing agent is used. To analyze the filling of pores after the CD process, the surface morphology of the samples was studied using a Zeiss Crossbeam 540 scanning microscope. The crystallographic structure of SnO₂/SiO₂/Si nanostructures with SnO₂ nanopore filling was studied by X-ray diffraction. X-ray diffraction analysis (XRD) is carried out on a Rigaku SmartLab X-ray diffractometer. As a result, a SnO₂-NW/SiO₂/Si nanoheterostructure with an orthorhombic crystal structure of SnO₂ nanowires was obtained. Photoluminescence (PL) spectra were measured upon excitation with light at a wavelength of 240 nm using a CM2203 spectrofluorimeter (Solar). Gaussian decomposition of the photoluminescence spectrum of SnO₂-NW/SiO₂/Si structures showed that they have low intensity, which is mainly due to the presence of defects such as oxygen vacancies, interstitial tin or tin with damaged bonds. Electrical characterization studies were performed using a VersaStat 3 potentiostat (Ametek). Measurement of the current-voltage characteristic showed that the resulting SnO₂-NW/SiO₂/Si nanoheterostructure contains arrays of p-n junctions.

We investigated the electronic structure of Mg-, Si-, and Zn-doped four-faceted [001]- and [110]-oriented SnO₂ nanowires using first-principles calculations based on the linear combination of atomic orbitals (LCAO) method. This approach, employing atomic-centered Gaussian-type functions as a basis set, was combined with hybrid density functional theory (DFT). Our results show qualitative agreement in predicting the formation of stable point defects due to atom substitutions on the surface of the SnO₂ nanowire. Doping induces substantial atomic relaxation in the nanowires, changes in the covalency of the dopant–oxygen bond, and additional charge redistribution between the dopant and nanowire. Furthermore, our calculations reveal a narrowing of the band gap resulting from the emergence of midgap states induced by the incorporated defects. This study provides insights into the altered electronic properties caused by Mg, Si, and Zn doping, contributing to the further design of SnO₂ nanowires for advanced electronic, optoelectronic, photovoltaic, and photocatalytic applications.

Electrochemical deposition into a prepared SiO₂/Si-p ion track template was used to make orthorhombic SnO₂ vertical nanowires (NWs) for this study. As a result, a SnO₂-NWs/SiO₂/Si nanoheterostructure with an orthorhombic crystal structure of SnO₂ nanowires was obtained. Photoluminescence excited by light with a wavelength of 240 nm has a low intensity, arising mainly due to defects such as oxygen vacancies and interstitial tin or tin with damaged bonds. The current–voltage characteristic measurement showed that the SnO₂-NWs/SiO₂/Si nanoheterostructure made this way has many p-n junctions.