Atomic-scale conversion of clean Si(111):H-1×1 to Si(111)-2×1 by electron-stimulated desorption

Tunneling images of the ideal Si(111):H-1×{}1 surface exhibit features and electronic structure consistent with a simple termination of the surface dangling bonds by atomic hydrogen. Bombardment of the surface with low-energy (2--10 eV) electrons desorbs the hydrogen, converting the 1×{}1 surface phase to the 2×{}1 {π}-bonded chain. The efficiency of this process versus electron kinetic energy indicates that the desorption is mediated by promoting electrons from the {σ} to the σ* band. The resultant increase in surface free energy drives a spontaneous phase transition to the 2×{}1. Individual 2×{}1 regions as small as ten surface sites have been created in this fashion.