Crystallinity and Epitaxy of Evaporated Germanium Films on Sodium Chloride Substrates

Abstract

Using transmission electron microscopy and electron diffraction techniques, the crystallinity and the epitaxy of Ge films deposited on (001) NaCl substrates in 2×10-8 Torr have been investigated as a function of deposition rate, substrate temperature, and substrate surface condition such as vacuumcleaved, air-cleaved, or electron-beam bombarded. For the vacuum-cleaved substrate, the linear relation observed between the logarithm of the deposition rate and the reciprocal of the amorphous to crystalline transition temperature agrees with Blakely's surface diffusion theory, and yields an activation energy of surface diffusion of Ge on NaCl of 2.03 eV. The observed linear relation between the logarithm of the deposition rate and the reciprocal of the epitaxial temperature agrees with Walton's nucleation theory of small cluster, and leads to an activation energy of 1.79 eV.