Low Pressure Chemical Vapor Deposition of TiO₂ Layer in Hydrogen-Ambient

Abstract

Low pressure chemical vapor deposition (LPCVD) of anatase TiO 2 as a reduction gas was demonstrated at pres- sure of 3 mtorr in comparison to that using TTIP and O 2 with study for the property of the layers. Dissociation energy of TTIP in H 2 was higher than that in O 2 but resistivity of the layer deposited in H 2 was significantly decreased to 0.2 Ω cm in contrast to the high resistivity beyond 100 Ω cm of the layer deposited in O 2 . UV-Vis optical transmission spectra showed absorption around 2.2 eV was increased in the layer deposited by TTIP + H 2 in addition to decrease of forbidden energy gap due to increase of Urbach tail. Resistivity at low temperature below 100 K indicating the layer deposited in H 2 -ambient was degenerated by the high electron density but the resistivity was decreased with temperature above 100 K with the activation energy about 100 meV. A possible electronic conduction model based on kernel, grain boundary and surface trap to clarify the temperature dependent resistivity suggesting resistivity of the layer was limited by depletion region in the grain-boundary extended from the surface and the kernel with significantly low resistivity in 10 -3 Ω cm order was formed in the layer.