Imaging of oxide and interface charges in SiO₂-Si

Charges arising from single electrons and holes localized in SiO2 gate oxides and at the SiO2-Si(1 1 1) interface were imaged with a non-contact atomic force microscope (AFM). The polarity of the charge was ascertained from simultaneously recorded Kelvin images. The bias dependent position of the Fermi level controls the trap occupancy in general, as well as the state of charge of interface states (Pb centers) and their polarity. Temporary trap occupancy caused by the extreme band bending beneath the AFM tip can lead to an appreciable enhancement in the apparent resolution of the charge image. © 2001 Elsevier Science B.V. All rights reserved.