The d.c. conductivity of vacuum evaporated amorphous silicon f'rims has been measured. A model based on the properties of (111) surface states of cleaved crystalline Si is used to interpret this data as well as other data found in literature.
FILMS of amorphous Si evaporated or sputtered onto room temperature substrates exhibit an extrinsic-like conduction process, 1 an optical absorption 1-8 down to hv ~ 0.5 eV, a bulk distribution of density deficient regions, referred to as voids, 4 and an electron spin resonance (ESR) signal. 1 When these films are annealed, decreases are measured in the electrical conductivity, infrared optical absorption, ESR signal and total void volume. 1'4 The ESR signal is thought to arise from electrons on the void surfaces. 1 Similar electrical and optical effects have been noted in amorphous Ge films. 5-7 High resolution electron microscopy 8 shows that the voids in Ge form an interconnected network, and that the interconnectedness remains with increasing deposition temperature even though the total void volume had decreased. It is reasonable to assume that voids in amorphous Si f'rims are also interconnected.