Scanning tunneling microscopy study on the surface and interface of Si(111)/SiO2 structures

Scanning tunneling microscopy was used to investigate the surface and interface of Si(111)/SiO2 structures. The oxide thickness ranged from 0.3 to 1.7 nm. The surface was observed using a sample bias larger than 4.0 V. Fourier transform spectra of the surface images showed clear seventh order spots originating from the Si(111)7×7 reconstruction, indicating that 2.7 nm periodicity of the reconstruction remains on the oxide surface. At a sample bias of less than 4.0 V, a Si(111)/SiO2 interface was observed when 0.3-nm-thick oxide was partially left on the Si surface.