Local charge redistribution at potassium adsorption on the Si(111)7x7 surface: a scanning tunneling microscopy study

The adsorption process of potassium on the Si(111)7 x 7 surface has been st udied by scanning tunneling microscopy (STM). The adsorption of K proceeds in two stages. in the first stage K atoms adsorb ionically with their s-sta tes above E-F and the charge transfer occurs efficiently on the faulted hal ves. The first adlayer develops to the entire faulted and unfaulted regions with the K-induced states above E-F. At higher coverages (the second stage ), K atoms tend to form neutral clusters preferentially in faulted regions. The electronic structure around the clusters is markedly modified, which s uggests a local charge redistribution. The STM observations well explain me asured work function variation. (C) 1999 Elsevier Science B.V. All rights r eserved.