ELECTRICAL AND OPTICAL-PROPERTIES OF IN-SITU HYDROGEN-REDUCED TITANIUM-DIOXIDE THIN-FILMS DEPOSITED BY PULSED EXCIMER-LASER ABLATION

Thin films of TiO2-x were deposited on Si and glass substrates by the pulsed excimer laser ablation technique at different hydrogen-ambient pressures and substrate temperatures. The electrical conductivity of the films was studied in the low-temperature region up to 100 K. At room temperature we could lower the resistivity of TiO2 about 17-18 orders of magnitude by in situ reduction. The average activation energies obtained are in the range of 0.008 to 0.160 eV with a change in the slope of the log sigma vs. 1/T curve around the temperature of 180-200 K, except in the film deposited at a hydrogen pressure of 13.3 Pa and substrate temperature of 400-degrees-C, which is linear throughout the measured temperature range. X-Ray diffraction patterns of the films showed that the films contained mixed Ti-O phases. The optical properties such as refractive index. absorption coefficient, transmission and reflection were investigated and found to be strongly dependent on the degree of reduction, ia.e. change in the composition of TiO2-x.