Improved chemical and electrical stability of gold silicon contacts via epitaxial electrodeposition

The ballistic transport and junction stability of epitaxial Au, grown on Si (111) and (001) substrates via electrodeposition, have been investigated as a function of Au thickness (6.7-14.1 nm). Scanning tunneling microscopy (STM) with ballistic emission electron microscopy (BEEM) showed hot electron transmission for diodes with Au thicknesses greater than 7 nm, whereas for thinner samples surface or interfacial oxidation meant that macroscopic current-voltage characteristics gave high barrier heights (0.8 eV) but no detectable BEEM transport at room temperature. Diodes that remained electrically stable for several months after exposure to air also show an atomically abrupt and epitaxial Au/Si interface via cross-sectional transmission electron microscopy. Degradation in rectifying diode properties through surface or interfacial reactions is indicated by poorer STM images and decreasing or no BEEM transmission, correlated with the formation of a continuous interfacial layer.