Nanometer-scale creation and characterization of trapped charge in SiO2 films using ballistic electron emission microscopy

Electron injection into similar to 25 nm thick SiO2 films in Pt/SiO2/Si structures using ballistic electron emission microscopy (BEEM) is found to produce a local suppression in the BEEM current, which is at least partly due to electron trapping in the SiO2 film. Measured variations in the BEEM threshold voltage with the voltage applied across the SiO2 film can be used to estimate the local trapped electron density and the centroid location, which agree with macroscopic measurements. Our measurements indicate that BEEM can be sensitive to very small numbers of electrons trapped in buried SiO2 films.