Physical Properties of Ba0.95Pb0.05TiO3+0.1%Co2O3
The single-phase perovskite structure of the Ba0.95Pb0.05TiO3+0.1%Co2O3 ceramics was confirmed by the X-ray diffraction method. Microstructural studies revealed that the samples were of good quality and chemically homogeneous. The thermal behaviour of ceramics was studied using the in situ high-temperature X-ray synchrotron powder diffraction investigation. The energy gap of about 3.2 eV was estimated using a reflectance spectroscopy. Measurements showed the influence of Pb and Co on the character of phase transition in the BaTiO3 structure. The results were compared to the ones obtained for pure BaTiO3.
Defect-related photoluminescence and photoluminescence excitation as a method to study the excitonic bandgap of AlN epitaxial layers: Experimental and ab initio analysis
We report defect-related photoluminescence (PL) and its vacuum ultraviolet photoluminescence excitation (PLE) spectra of aluminum nitride layers with various layer thicknesses and dislocation densities grown on two different substrates: sapphire and silicon. The defect-related transitions have been distinguished and examined in the emission and excitation spectra investigated under synchrotron radiation. The broad PL bands of two defect levels in the AlN were detected at around 3 eV and 4 eV. In the PLE spectra of these bands, a sharp excitonic peak originating most probably from the A-exciton of AlN was clearly visible. Taking into account the exciton binding energy, the measurements allow…