Origin of the apparent (2×1) topography of the Si(100)-c(4×2) surface observed in low-temperature STM images

Abstract

Low-temperature scanning tunneling microscope (STM) images of the Si(100) surface showing apparent (2×1) atom dimer lines have recently been reported. Using experimental and theoretical approaches, it is demonstrated how those (2×1)-like images result from a c(4×2) surface reconstruction imaged at high bias voltages. In the STM junction, the surface contribution of 3px surface-state electronic resonances relative to the 3p z states is bias voltage dependent. The apparent (2×1) STM images result from an increase in the number of bulk Si electronic channels amplifying Si(100)-c(4×2) surface 3px surface states contribution to the tunneling current with respect to the one of 3pz states. © 2011 American Physical Society.