Spatially and Energy Resolved Hot Electron Transport Through Metal-Oxide-Silicon Structures

The tip of a scanning tunneling microscope was used to inject hot electrons into thin Pd layers of Pd-SiO(sub2) structures incorporating 75-150 A-overcircle thermally grown oxides. The collector currents emanating from the n-type Si(100) substrates for tip biases V(subT)greater-than or equal to 4 eV were measured as a function of eV(subT) (electron energy) for different oxide biases V(subox) applied independently across the oxide layers. Threshold shifts with increasing positive V(subox) were observed for the first time and are attributed to image force lowering of the oxide potential near the metal-oxide interface. The shifts agree well with those predicted by classical image force theory. A zero field threshold energy of 3.99 plusmin0.02 eV for the Pd-SiO(sub2) interface was deduced. Image force effects were also incorporated into Monte Carlo calculations of the energy dependent electron transmission probability T(subox) across a 150 A-overcircle oxide. Faborable comparisons with experiment are observed.