Interfacial scattering of hot electrons in ultrathin Au/Co films

We have used room-temperature, ballistic electron emission microscopy (BEEM) to measure hot-electron transport through ultrathin Au/Co multilayer structures deposited onto Si. The samples consist of Au/Co/Si or (Au/Co)n/Au/Si diodes, sputter deposited at 175 or 300 K, where n is the number of repeat layers. The thin-film Co attenuation length, λCo, is extracted from the BEEM spectra as a function of Co thickness, in single Co layer samples. Similarly, the interface attenuation number, or the number of Co/Au interfaces required for a 1/e attenuation, is determined from the multi-interface samples. BEEM barrier heights of Au/Co/Si decrease with increasing Co thickness (for thicknesses <1 nm), as the film becomes continuous and develops a Schottky barrier for Co or CoSi2(<0.7 eV). For these diodes, λCo, increases from 0.3 to 0.5 nm, each with an estimated uncertainty of 0.1 nm, when the deposition temperature is decreased from 300 to 175K. This result is associated with decreased silicide formation at the lo...