CHARACTERISTICS OF TITANIUM-OXIDE FILMS DEPOSITED BY AN ACTIVATED REACTIVE EVAPORATION METHOD

Titanium di- and sesquioxide films were epitaxially grown on the (001) surface of sapphire single-crystalline substrates by an activated reactive evaporation method. Formation range for each titanium oxide was determined as a function of oxygen pressure (P(O2)) by means of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films prepared at P(O2) greater-than-or-equal-to 2.0 X 10(-4) Torr were stoichiometric (100)-oriented rutile of TiO2, and with decreasing P(O2) they would accommodate more and more Ti3+ ions in the rutile structure. At P(O2) = 0.6 X 10(-4) Torr, on the other hand, (001)-oriented Ti2O3 Was formed and an electrical transition was clearly detected at about 400 K. However, the large lattice mismatch between the substrate and these films leads to a periodic introduction of misfit dislocations in the case of the TiO2 films and a mixing of stacking sequences for the Ti2O3 films.