Hot electron transport in SiO2 probed with a scanning tunnel microscope

Hot electrons injected with a scanning tunnel microscope (STM) tip into Pt/SiO2/Si(100) structures were detected as a collector current in the Si by using a STM configuration known as ballistic electron emission microscopy. The collector current, observed for STM tip potentials ≳4 V and for oxide biases ≥0 V, is direct evidence for electron transmission through the conduction band of the SiO2. Negative oxide biases delayed the onset of current to correspondingly higher tip potentials. A simple model was used to extract the energy and bias dependent transmission probabilities from the experimental data for a 62 Å SiO2 layer. The results are compared with Monte Carlo calculations.