Growth kinetics of amorphous interlayers in Ti thin films on epitaxial Si-Ge layers on silicon and germanium

The growth kinetics of amorphous interlayers (a interlayers) formed by solid-state diffusion in ultrahigh vacuum deposited polycrystalline Ti thin films on germanium and epitaxial Si1-xGex (x = 0.3, 0.4 and 0.7) alloys grown on (001) Si and (111) Ge has been investigated by transmission electron microscopy and Auger electron spectroscopy. The growth of a interlayers in all systems was found to follow a linear growth behavior initially. The activation energies for the linear growth of a interlayers were found to decrease with the Ge content and are 1.0 +/-0.2, 0.95 +/-0.2, 0.85 +/-0.2, and 0.7 +/-0.2 eV for Ti/Si0.7Ge0.3, Ti/Si0.6Ge0.4, Ti/Si0.3Ge0.7, and Ti/Ge systems, respectively. The maximum thickness of a interlayer was found to increase with the Ge content with x less than or equal to0.4. On the other hand, the formation temperature of crystalline phase was observed to decrease with the Ge content. Essential factors for the formation and growth of a interlayer are discussed. The results are compared with the Ti/Si system. (C) 2001 American Institute of Physics.