Optical Study of Ultrathin TiO2 Films for Photovoltaic and Gas Sensing Applications

TiO2 ultrathin films of thickness below 20 nm were deposited by reactive RF magnetron sputtering. The optical properties of TiO2 films were investigated by various optical techniques including UV-VIS-NIR spectroscopic ellipsometry. The Scanning Probe Microscopy (SPM) was used to determine thickness and surface roughness of the deposited films. The correlation between preparation conditions of ultrathin TiO2 films and their physical properties has been studied. The analysis of optical data revealed the parameters of deposited films and intrinsic properties of TiO2 material before and after annealing. We found that deposited layers were predominantly amorphous with high porosity at the top sample, and absence of porosity at the bottom of TiO2 layer. Annealing considerably improves structural order of the studied samples and the film transforms to the polycrystalline anatase phase. Also we evaluated the energy bandgap (about 3.1 eV – 3.2 eV) which increases after annealing (above 3.3 eV) and it is  close to the bandgap of anatase. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6328</p

Mechanikos laboratoriniai darbai nespecialistams : mokymo metodinė priemonė

Vytauto Didžiojo universitetasŠvietimo akademij

Mechanikos laboratoriniai darbai nespecialistams [Elektroninis išteklius] : metodinė priemonė

Vytauto Didžiojo universitetasŠvietimo akademij

Optical properties of the BiSI crystal

Vytauto Didžiojo universitetasŠvietimo akademij

Electronic structure and optical properties of BiSI crystal

Electronic structure and optical properties of BiSI crystal were investigated by the full potential linearized augmented plane wave (FL-LAPW) method with density functional theory (DFT). The complex dielectric function and optical constants, such as optical absorption coefficient, refractive index, extinction coefficient, energy-loss spectrum and reflectivity, were calculated. The optical properties of BiSI crystal were studied experimentally by spectroscopic ellipsometry. The experimental results were compared with the theoretical spectra of complex dielectric functions and with the spectra of a pseudo-dielectric function (PDF). This method shows that experimental spectra consist of four Laurence lines sumVytauto Didžiojo universitetasŠvietimo akademij

Silicon Nanostructures For Efficient Light Absorption In Photovoltaic Devices

Porous silicon light trapping layers (por-Si LTL) were manufactured using electrochemical etching. Optical measurements have shown the improved por-Si LTL optical properties versus bulk silicon. The p-n junction was formed by boron diffusion from borosilicate glasses. Scanning Kelvin Force Microscopy (SKFM) and Tunnelling Atomic Force Microscopy (TUNA) techniques were used to determine the location of p-n junction in samples with porous silicon light trapping layers. DOI: http://dx.doi.org/10.5755/j01.ms.20.2.6326</p

Optical response of La1-xMnO3/Al2O3 films

La1-xMnO3 films grown by metal organic chemical vapor deposition technique on r-plane cut Al2O3 substrates were investigated. The change of the optical response over the La1-xMnO3/Al2O3 sample surface was investigated along with the temperature dependence of magnetization. The mostly pronounced difference in the spectra of dielectric function occurred in the region of the d-d transitions of Mn-ions. The changes in the optical spectra and magnetic properties were correlated to the structural features of thin film