Scanning tunnelling microscopy study on hydrogen removal from Si(0 0 1)-(2 × 1):H surface excited with low-energy electron beams

Direct atomic-scale imaging using scanning tunnelling microscopy (STM) shows the formation of un-terminated single dangling bond (DB) on Si(0 0 1)-(2 × 1):H irradiated with low-energy electron beams below 13 eV. The concentration of DB sites increases initially with excitation dose, followed by saturation at the levels that depend on the beam-current density. It is shown that re-termination of DBs with hydrogen, accelerated under electron irradiation, is responsible for the saturation. We conclude that re-terminating hydrogen is issued from bulk of Si. Quantitative analyses of the results determine the precise Si-H bond rupture cross section to be 1.3 × 10−20 cm2, which is constant for electron energy from 2.6 to 12.6 eV. Mechanism of Si-H bond rupture is discussed based on the results.