Band-bending effects on scanning tunneling microscope images of subsurface dopants: First-principles calculations

摘要

Tip-induced band-bending (TIBB) effects on scanning tunneling microscope (STM) images have been investigated. The TIBB has an extremal value where the surface space charge layer turns from the inversion region to the depletion one with increasing dopant concentration at a fixed sample bias. Unignorable TIBB remains even for the usual degenerate semiconductor with a dopant concentration such as 10~(18) cm~(-3) for Si. The STM images for H-terminated Si(111) surfaces with dopants substituted at the subsurface have been simulated using first-principles calculations within the density functional theory. The subsurface dopants on the STM images become distinguishable more obviously in consideration of the TIBB effect, specifically for acceptors in the occupied state images and for donors in the empty state. As a result, the TIBB effect improves agreement between the experimental and the theoretical sample biases at which the dopant's feature can be observed clearly.