ELECTRONIC TRANSPORT IN EPITAXIAL FILMS STUDIED BY SCANNING PROBE TECHNIQUES

Abstract

Hot electron transport in epitaxial CoSi2/Si heterostructures has been studied in situ by ballistic electron emission microscopy (BEEM) at 77 K. At CoSi2/Si(111) interfaces elastic scattering at interfacial defects could be imaged with spatial resolution on a nanometer scale. Hot electron injection across CoSi2/n-Si(111) interfaces was found to be favored by interface scattering, in contrast to hot hole injection across CoSi2/p-Si(111) , in agreement with expectations based on the projected Si band structure. Inelastic scattering within the metal film was found to become dominant at energies above ~4 eV, leading to a strong sensitivity of the BEEM current on film thickness variations. This could be exploited to generate maps of the film thickness distribution, facilitating the interpretation of quantum size effects (QSE's) which appear both in BEEM and in scanning tunneling spectroscopy. The variation of the BEEM current was found to be entirely due to scattering effects at CoSi2/Si(111) interfaces, the Schottky barrier height being constant. At CoSi2/Si(100) interfaces, however, a pronounced decrease in the Schottky barrier height was observed at certain interfacial defects, some of which are not yet identified.