Electron Tunneling through SiO₂/Si Structures in Scanning Tunneling Microscopy

We study electron tunneling through SiO 2 /Si(001) structures in scanning tunneling microscopy (STM), where the oxide thickness ranges from 0.6 to 2.7 nm. Electron tunneling probabilities through the structures are calculated by employing an exactly solvable one-dimensional model. The calculation reproduces the measured I – V characteristics very well. It is shown by experiment and calculation that a region covered by SiO 2 is seen as a higher patch than the Si bare surface in a STM topography (constant current mode measurement). The apparent SiO 2 “thickness” in STM topography is comparable to the calculated one for the 0.6 nm SiO 2 but appears to be much thinner than the calculated one for the 2.7 nm SiO 2 . Origin of the discrepancy is discussed in terms of the electron scattering at the interfaces and in the bulk of SiO 2 films.