Electrical and mechanical properties of nitrided sol-gel derived TiO2 and SiO2-TiO2 films

The results of measurements of electrical conductivity for titanium-nitride films prepared by the ammonolysis of sol-gel derived TiO2 and SiO2-TiO2 coatings are presented. Sol-gel derived films on silicon and quartz substrates were nitrided by ammonia treatment in the temperature range from 500 to 1200 degrees C. The dc conductivity of nitrided films has been measured from 10 K to 900 K. It was found that conductivity is related to the amount of TiO2, which is converted to TiN during ammonolysis. In this way it is possible to change the electrical conductivity of samples by many orders of magnitude. The observed activation energy of the samples containing large amounts of TiN is below 0.1 eV. This indicates that the conductivity mechanism may be interpreted as electrons tunnelling between metallic TiN granules. The mechanical properties were evaluated by a nanoidentometric technique. The results of nanoidentometric measurements confirm an increase in microhardness and Young's modulus for nitrided SiO2-TiO2 films containing large amounts of TiN.