Field ion-scanning tunneling microscopy of alkali metal adsorption on the Si(100) surface

Abstract

We have constructed a scanning tunneling microscope (STM) equipped with a field ion microscope (FIM), by which one can monitor and shape the STM probe tip on an atomic scale in situ in the STM chamber. Taking advantage of a well-defined tip prepared by a FIM, we have greatly improved the stability and reproducibility of the performance of the STM. Li and K adsorption on the Si(001) 2×1 surface has been investigated by field ion-scanning tunneling microscopy (FI-STM). The STM images have shown that at the initial stage of adsorption, Li (K) atoms (1) adsorb on top of one of the dimer-forming Si surface atoms and (2) stabilize the asymmetric (buckled) dimerization, and (3) form linear chains, perpendicular to the substrate 2×1 dimer rows. Our observations suggest that alkali metal adsorption on the Si(001) 2×1 surface may be significantly different from the conclusions of earlier reports.