Cubic crystals in ti films evaporated on nacl substrates

The growth and structure of Ti films evaporated on NaCl substrates have been studied by electron microscopy. The film showed cubic or fcc-like diffraction spots of three types in the early growth stage, depending on the preparation method and temperature of the substrate and film thickness. The lattice parameters corresponding to those spots taken from 2 nm-thick films formed on the substrate at 260°C were a=0.441 nm, 0.418 nm and 0.426 nm, which were determined to be those of CaF₂-type TiH_1.5, NaCl-type TiO_1.0 and some titanium compound, respectively. The former two grew on the substrate cleaved in vacuum while the last one grew on that cleaved in air, only. When the film was thicker than 3 nm, hcp diffraction spots also appeared. The formation mechanism of the cubic and hcp crystallites is discussed.