Structural characterization of Ti-Si thin film superlattices.

Thin films of amorphous/polycrystalline Ti layers alternating with amorphous Si have been grown on room-temperature {001}Si substrates by electron beam evaporation. Cross-section transmission electron microscopy of these films indicates that the depositon results in the formation of ultra-thin superlattice layers with no cumulative roughening and with atomically abrupt interfaces. The crystallinity of the Ti layers is found to depend on the layer thickness. For thicknesses =20angstroms the Ti appears amorphous, whereas layers thicker than ~40angstroms consist of polycrystalline hexagonal Ti grains exhibiting a (0001) preferred orientation parallel to the interfaces.