Temperature study of phase coexistence in the system Pb on an Si(111) surface

The temperature-dependent coexistence of Si0.28Pb0.72/Si(111) and Si(111)-( 1 x 1)-Pb phases was investigated using scanning tunneling microscopy. An a rea of (1 x 1)-Pb islands was monitored as a function of temperature rangin g from room temperature up to 400 degrees C. The movie strategy was applied in order to acquire successive images of a selected region. It was found t hat this area fluctuates quasi-periodically in time, with amplitude dependi ng on temperature. The strongest fluctuations (up to 10% of the mean area v alue) were observed at 210 degrees C. These fluctuations were restricted to the defect-free parts of the island perimeter, the rest of the (1 x 1)-Pb phase being stable. A further increase in temperature lead to a monotonous temperature-dependent decrease in (1 x 1)-Pb areas. This decrease was obser ved to be strongly tip-influenced at temperatures slightly above 210 degree s C, while at higher temperatures the desorption of Pb atoms prevailed. (C) 2000 Elsevier Science B.V. All rights reserved.