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 (Po2) by means of x-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Films prepared at Po^.OX 10 4 Torr were stoichiometric (lOO)-oriented rutile of Ti02, and with decreasing Po2 they would accommodate more and more Ti3+ ions in the rutile structure. At P02 = 0.6 X 10~4 Torr, on the other hand, (OOl)-oriented Ti203 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 Ti02 films and a mixing of stacking sequences for the Ti203 films.