Abstract
Adsorption and diffusion of single hydrogen atoms on Si(111)-(7 × 7) surfaces at elevated temperatures have been studied using scanning tunneling microscopy. Hydrogen atoms adsorb preferentially atop rest atoms. An adsorbed H atom can hop between two neighbor rest atoms via an adatom, i.e., via a metastable intermediate state. Below 340 °C, the hopping is mostly confined within a half-cell, but at higher temperatures, they can hop across the cell boundary. The activation energies for different hopping paths were measured. The binding energy difference between rest-atom and adatom sites and that between corner and edge adatom sites were also determined to be ∼0.2 and ∼0.05 eV, respectively.