Epitaxial Growth of Titanium Thin Films

Single crystal thin films of titanium have been epitaxially grown on NaCl substrates of three different orientations [(001), (110), (111)]. At thicknesses above 500 Å, the normal hexagonal close-packed structure is obtained. Below approximately 350 Å, the metal is seen to grow in a previously unreported face-centered cubic structure with the lattice parameter, ao = 4.33 Å. This structure is thought to result from pseudomorphic type growth on the NaCl substrate in keeping with proposed misfit theories. At a critical thickness (∼200–300 Å), there is a transformation from the fcc phase to the normal hcp phase in deposits on the (001) and (111) substrate surfaces. The deposit on the (110) NaCl surface demonstrated a coexistence of fcc and hcp material at all thicknesses.