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

Abstract

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 TiH_x 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 TiH_x 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.