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Zinc oxide (ZnO) and titanium oxide (TiO2) are two widely studied metal oxide semiconductors due to their unique optical, electronic, and catalytic properties. These materials have attracted considerable interest in the development of advanced electronic device like sensors, solar cells, and photocatalysts, among other applications. Nanostructured thin films of ZnO and TiO2, with thicknesses ranging from a few to several hundred nanometres, have received increasing attention in recent years due to their exceptional properties arising from the quantum confinement and large surface area-to-volume ratio. These properties include enhanced optical absorption, improved charge transport, and increased reactivity, making them suitable for the above-mentioned various applications. In this work several chemical and physical methods of synthesis were utilized to produce nanostructured thin films, which were thoroughly characterized by SEM, STEM, TEM, AFM, GIXRD, UV- Vis, DLTS and ss-IS, and used in advanced configurations of thin-film based solar cells (perovskite) and as immobilized photocatalysts.

Environmental pollution and absence of cost- effective and renewable energy resources are well- acknowledged problems nowadays. As a consequence, development of a low-cost, clean, energy-efficient and sustainable technologies is required. One of the possibilities is photocatalysis because titanium dioxide is environmentally friendly, chemically stable, commercially available, non- toxic and efficient photocatalyst, widely used for water and air purification. Titanium dioxide is a powerful photocatalyst that is chemically stable, non-toxic, and extremely reactive. It has been used for water purification, pesticide removal, degradation of air pollutants, water splitting, etc. [1] Another benefit is the flexibility to tune TiO2’s size and shape. Nanostructured TiO2 has a higher surface-to-volume ratio, different chemical and physical characteristics than bulk TiO2, and longer diffusion lengths and lifetimes of photogenerated charge carriers (electrons and holes), all of which contribute to improved photocatalytic efficiency. Electrochemical anodization of titanium foil is a low-cost, simple, fast, and scalable method for producing TiO2 nanotube arrays with the ability to manipulate the material's morphology [2]. Synthesized immobilized nanoporous TiO2 photocatalysts, prepared by electrochemical anodization of titanium foils, were modified by wet–impregnation by immersing samples for 5 hours in five different solutions containing various Cu concentrations (0.2 – 1 M). The objective of this research was to investigate how modification with Cu compounds can improve the photocatalytic activity of immobilized nanoporous TiO2 under the UV/Vis light irradiation. Furthermore, correlation of photocatalytic activity and different Cu concentrations was studied. In order to identify an optimal Cu concentration needed for the most efficient photocatalytic degradation of imidacloprid, photocatalytic activity of the unmodified reference (0M_Cu_TiO2) and five Cu- modified (0.2, 0.4, 0.6, 0.8 and 1M) samples was evaluated by monitoring degradation of imidacloprid using SPC and a full-spectrum compact fluorescent bulb with high UVB intensity. The photodegradation process was modelled using a pseudo-first-order kinetics (Eq. 1): ln (C/C0) = - kt (1) In order to resolve the Cu valence state and local symmetry in samples, XANES spectra were analysed with IFEFFIT program package Athena using standard procedure [3]. The best results determining the average valence state of the Cu atom in the samples, obtained by fitting XANES spectra of proper reference compounds with known valence state of the element, similar symmetry, and same type of neighbour atoms in the nearest coordination shells that are arranged in the same local structure, are shown in Fig. 2. XANES results showed that Cu species are in divalent form and have distorted octahedral structure, where Cu(II) cations are located in the centre of Jahn–Teller tetragonally distorted octahedron of six oxygen atoms. With the aim of determining the local structure around the Cu(II) ions, Cu-K edge EXAFS analysis was done. Fourier transforms (FT) of the k2 weighted EXAFS spectra of the photocatalyst samples are shown in Fig. 3. Peaks observed in the FT spectra in a range of 1 to 3.8 Å represent a contribution of photoelectron backscattering on the nearest shells of Cu neighbouring atoms. For the quantitative analysis, a FEFF [4] model was constructed. The results show that Cu atoms are coordinated to six oxygen atoms in a distorted octahedron. Four O atoms are at shorter Cu–O distance (~1.95 Å) and two O atoms at longer distance (2.3 – 2.6 Å) on axial positions. The second shell of neighbours is comprised of Ti atoms at ~2.95 Å and Cu and O atoms distributed from 3.1 Å to 3.7 Å. The Cu(II) forms Ti–O–Cu and Cu–O–Cu connections which indicates that a part of the Cu(II) is attached to the surface of TiO2 and in the form of CuO nanoparticles.

In this work we investigated Cu modified immobilized photocatalysts based on TiO2 nanotubes, used for the degradation of imidacloprid. Specifically, we paid attention to the role of Cu(II) ions, namely their local structure and chemical state in the photocatalyst. The photocatalysts were prepared by electrochemical anodization and modified using Cu solutions with various Cu concentrations (0.2– 1.0 M). Morphology and structure of the derived photocatalysts were characterized by X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-ray, UV-VIS-NIR, Raman and Photoluminescence spectroscopies. Particularity detailed was the X-ray absorption spectroscopy analysis: extended X-ray absorption fine structure and X-ray absorption near edge structure. The EXAFS results indicated the formation of Ti–O–Cu connections, suggesting that the Cu(II) cations are attached to TiO2 surface which contributes to the improvement of the photocatalytic activity.

We report on the metastable defects introduced in the n-type 4H-SiC material by epithermal and fast neutron irradiation. The epithermal and fast neutron irradiation defects in 4H-SiC are much less explored compared to electron or proton irradiation-induced defects. In addition to the carbon vacancy (Vc), silicon vacancy (Vsi) and carbon antisite-carbon vacancy (CAV) complex, the neutron irradiation has introduced four deep-level defects, all arising from the metastable defect, the M-center. The metastable deep-level defects were investigated by deep level transient spectroscopy (DLTS), high-resolution Laplace DLTS (L-DLTS) and isothermal DLTS. The existence of the fourth deep-level defect, M4, recently observed in ion-implanted 4H-SiC, has been additionally confirmed in neutron-irradiated samples. The isothermal DLTS technique has been proven as a useful tool for studying the metastable defects.

We report on response of newly designed 4H-SiC Schottky barrier diode (SBD) detector to alpha, beta and gamma particles. In order to optimize SiC SBD detector’s thermal neutron efficiency, it’s of particular importance to understand its behavior in various radiation fields. The optimal size of the SBD is limited by degradation of electronic properties, and consequently their charge particle detection. We have manufactured diodes up to 3 x 3 mm active surface area to study those properties in correlation with increasing of detector size. Approximately 25 µm thick epitaxial layer is grown on SiC substrate by chemical vapor deposition, which is sufficient to stop alpha particles up to 6.8 MeV. Different active volume sizes of the detector based have been electrically characterized and exposed to radiation fields of alpha, beta and gamma particles. Extensive studies of the detector response to the various alpha emitters in the 3.27 MeV to 8.79 MeV energy range have been carried out. Results presented here demonstrate not only excellent linear response of the different detector active area to alpha particles, but also shows linear response to gamma particles. The detectors show a linear energy response, high charge collection efficiency and high energy resolution for the alpha particle energies bellow 6.7 MeV which is in a correlation with the range of charged particles in epitaxial layer of our detectors. Electrical characteristics of the detectors were assessed by temperature dependent current-voltage (I-V) and capacitance-voltage (C-V) measurements as well as by Laplace DLTS characterization of the electrically active defects. Ideality factor of the diodes is found to be in the range of 1.01 to 1.02 and free carrier concentration is in the range of 3x1014 cm-3 to 4.5x1014 cm-3. Co-60 and Cs-137 gamma radiations were carried out in Ruđer Bošković Institute’s Secondary Standard Dosimetry Laboratory with the air kerma rates up to 77 mGy/min., The 7th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications (ANIMMA2021)

Modern solid-state solar cells are multi-layered composites ; such configuration allows immense area for upgrades but not without struggle. As the main problem of all modern photovoltaic devices we find the mutual dependence of layers, i.e. the difficulty to predict the exact behaviour due to complex transport mechanisms at the boundaries between thin-film interfaced to other layers. Among such constituents, we find transparent electrodes or transparent conducting oxide layers (TCO), primarily aluminium doped zincite (AZO). AZO is a system thought to be well known, yet synthesis and deposition, chemical modifications, nano-morphological and nano-structural organisation parameters are still not unambiguously related to final functionality. For example, it is not clear how nanostructurisation of AZO would affect light trapping and vertical conductivity, while retaining of lateral conductivity for same thickness of films. The questions regarding general compatibility in interfacing of adjacent layers in SC also remain unclear. The benefits of AZO are thermal stability and mild deposition conditions. We follow these benefits and here we show evaluation of various softer chemical deposition methods for preparing AZO in planar configuration, as well as nanostructured, vertically aligned AZNR films that will retain conductivity, transparency and layer interconnectivity. The successfulness of the synthesis method was checked by means of GIXRD, FTIR-ATR and SEM/EDS. PL/DRS-UV-VIS and DLTS monitored compositional parameters behind transparency as well as lateral and perpendicular conductivity. In addition, parameters from profilometry, contact angle and TEM/EELS analysis shed more light on what synthesis seem to be more favourable for specific property. The utilisation of the observed parameters and behaviour was discussed from the point of view of TCO and CTO performing solar cell layers. The concept of developed material may shift the strategies of the solar cell design. This investigation of AZNR may cause the reconsideration of the paradigm of solar cell assembly since the AZNR additionally show conceptual similarities with charge transfer oxide (CTO) layers.

Pure and Al doped ZnO nanorods were prepared by a two-step chemical bath synthesis. The synthesis reposes on the deposition of a seed layer, i.e. spin coating of a thin-film of Zn solution on a silicon wafer in the first step, and on growing of the zincite nanorods (ZNRs), i.e. immersion of seed layer in an equimolar zinc nitrate and hexamethylenetetramine solution at elevated temperature for 1 h in the second step. For Al doped ZNRs the stoichiometry was adjusted by 3 at% of aluminium nitrate nonahydrate. The properties of the derived ZNRs and Al-doped-ZNRs thin-films were characterized by X-ray Diffraction (XRD), atomic force microscopy (AFM) and field emission gun scanning electron microscopy (FEG SEM) with energy dispersive X-ray spectroscopy (EDS). Structurally, the diffraction results point out to compositional differences of the nanorods as a result of the Al doping. Morphologic microscopy results are in concordance with diffraction data and additionally point out to a change in the geometry of the nanorods as a result of the Al doping. Electrical properties were examined by Kelvin probe force microscopy (KPFM) and by temperature-dependent current-voltage (I-V) measurements on Au/(Al)ZnO NR/n-Si junctions. The doping lead to an increase of conductivity of the ZnO NRs by an order of magnitude. The I-V characteristics for the pure and doped NRs follow the ohmic regime at lower voltages, while for the higher voltages the observed changes were attributed to the successful Al doping. The increase in the conductivity and shifting of the geometry of the nanorods can influence the overall electric transport properties which is a desirable behaviour in the area of photocatalysis and photovoltaics.

We present a study of electrically active radiation-induced defects formed in 4H-SiC epitaxial layers following irradiation with fast neutrons, as well as 600 keV H+ and 2 MeV He++ ion implantations. We also look at electron emission energies and mechanisms of the carbon vacancy in 4H-SiC by means of first-principles modelling. Combining the relative stability of carbon vacancies at different sites with the relative amplitude of the observed Laplace-DLTS peaks, we were able to connect Z1 and Z2 to emissions from double negatively charged carbon vacancies located at the h- and k-sites, respectively.