Electron emission microscopy on Au/Si and silicide/Si Schottky . Bamers

The scattering processes and the beam shapes of electrons transmitted through an ultrathin (5-35 nm) metal film are analyzed by ballistic electron emission microscopy (BEEM) using a scanning tunneling microscope. The metal film thickness is varied for the Schottky barrier system Au/Si for which the attenuation of the ballistic beam is analyzed. The shape of the emission current-voltage characteristics is found to be independent of the film thickness due to multiple reflections in the film and due to the lateral diffusion in the film. The attenuation in the film is superexponential. Scattering at the metal/metal interface is studied for the system Au(5 nm)/CoSi,(S nm)/Si. The double-metal layer system degrades the resolution of ballistic electron emission microscopy to approx. 10 nm, i.e. twice the metal film thickness corresponding to a random beam spread