Epitaxial cubic and hexagonal crystallites in titanium thin films evaporated onto sodium chloride substrates

Ti films of 10 nm thickness prepared by evaporation onto NaCl substrates at 250°C have been studied by high-resolution electron microscopy. The films have two characteristic regions: CaF2-type TiHx crystallites predominated, while h.c.p. Ti crystallites containing (1101) and/or (1011) twin boundaries grew in the other region. This is the first observation of {1101} twins in evaporated h.c.p. Ti films. Furthermore, misfit dislocations and a gentle bending of the TiH x lattice occurred at the interface between TiHx and h.c.p. Ti, owing to lattice mismatch strains. The orientation relationships and growth mechanism of the epitaxial films, especially of the h.c.p. Ti films, is discussed.