Direct Dimer-by-Dimer Identification of Clean and Monohydride Dimers on the Si(001) Surface by Scanning Tunneling Microscopy.

摘要

Atomic resolution images of clean Si(001)-(2xl) and the mono-hydride phase, Si(001)-(2xl)H were investigated using scanning tunneling microscopy at various sample-tip bias voltages. At a sample-tip bias of -1.9 V, each dimer of the monohydride phase show two protrusions 3.3 A apart separated by a minimum 0.11 A deep for a sample bias of -1.9 Volt, while clean dimers show a single protrusion per unit cell. Monohydride dimers appear lower than clean dimers, with apparent height differences ranging from 1.9 A at -1.6 V to 0.65 A at -3.0 V sample bias. An analysis of the apparent height and spatial distribution of tunneling current within each dimer can be used to unambiguously discriminate between clean dimers, monohydride dimers, and vacancy defects. This methodology is applied to study the distribution using disilane, revealing segregation of the monohydride into nearly isotropic islands.