Observation of Atomic Steps on Vicinal Si(111) Annealed in Hydrogen Gas Flow by Scanning Tunneling Microscopy

The surface of vicinal Si(111) annealed in H 2 flow was observed by equipping the chemical vapor deposition chamber with the scanning tunneling microscope. Samples were annealed at 1000°C for 10 min by passing an electric current under the H 2 pressure of 7 Torr. Their surface morphology was compared with those annealed in ultrahigh vacuum (UHV) and in N 2 flow at the same temperature. We found that the step motion during annealing in H 2 was obviously smaller than that for annealing in UHV and N 2 . The multisteps formed during the annealing in UHV and N 2 were not observed for H 2 annealing except in the case of heating by direct current in the direction of lower to higher terraces. The mechanism of the interruption of the step motion is discussed from the viewpoint of the interaction between the surface and hydrogen.