KINETICS OF HYDROGEN DESORPTION ON A SI(111) SURFACE

An in situ observation of hydrogen (H) desorption on a Si(lll) surface was carried out by using high temperature scanning tunneling microsco py (STM). There appeared a disordered phase with no atomic images arou nd 490 degrees C at which the surface monohydride started to desorb. W hen the sample temperature was maintained at a certain moment above 49 0 degrees C, the area of the disordered phase decreased with time and changed into a Si(111)-root 3 x root 3 R30 degrees structure. This beh avior of the surface structure can be explained by the migration of Si H species on an unreconstructed Si(111)-1 x 1 surface at elevated temp erature. Based on this behavior, we propose a model for the H desorpti on.