The excitation process of rare-earth ions in oxide semiconductors for optical emission is thought to be related to defect levels within the band-gap of the host material. In order to improve understanding of the role defect levels play in the energy transfer process, junction spectroscopy techniques can be used to investigate the electrically active emission centres. It has been reported that TiO2 is sensitive to humidity at low temperatures, such as those employed when conducting junction spectroscopy measurements. However, there are not many discussions how to prevent this effect and to improve the quality of measurements. After optimization of samples such as fabrication of flat surface and encupsulant for preventing external effect, temperature dependent-capacitance measurements (C-T) were carried out to characterise shallow traps formed within TiO2 band-gap. TiO2 and Sm-doped TiO2 thin films were deposited on SrTiO3 (100) templates by laser ablaton and rectifying Ruthenium Oxide Schottky diodes deposited on the TiO2 surface by laser ablation. A Sm or Sm-related shallow trap was observed in the Arrhenius plot of TiO2:Sm. In this paper, we show the optimized sample fabrication/preparation process that stabilizes the junction spectroscopy measurements, even in the presence of humidity and we present initial results obtained on samples using these optimized processing techniques.
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