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)-(1×1)-Pb phases was investigated using scanning tunneling microscopy. An area of (1×1)-Pb islands was monitored as a function of temperature ranging from room temperature up to 400°C. The movie strategy was applied in order to acquire successive images of a selected region. It was found that this area fluctuates quasi-periodically in time, with amplitude depending on temperature. The strongest fluctuations (up to 10% of the mean area value) were observed at 210°C. These fluctuations were restricted to the defect-free parts of the island perimeter, the rest of the (1×1)-Pb phase being stable. A further increase in temperature lead to a monotonous temperature-dependent decrease in (1×1)-Pb areas. This decrease was observed to be strongly tip-influenced at temperatures slightly above 210°C, while at higher temperatures the desorption of Pb atoms prevailed.