Time-resolved structural study of the Ge(111) high-temperature phase transition

Abstract

The dynamic behavior of the Ge(111) high-temperature phase transition has been investigated using 100 ps time-resolved reflection high-energy electron diffraction (RHEED). A laser pulse heats the surface while a synchronized electron pulse is used to obtain the surface diffraction pattern at some time during and after the heating laser pulse. For slow heating, the RHEED results show that the high-temperature phase transition spreads from ∼1020 K to ∼1070 K. For 100 ps laser heating, the time-resolved RHEED measurements show that the phase transition occurs in the transient temperature range from 1083±23 K to 1138±32 K. The time-resolved RHEED results are in agreement with incomplete melting in which only the topmost layer melts during the phase transition. Thus, overheating of the topmost bilayer beyond the onset temperature of incomplete melting by 63±23 K was observed for 100 ps laser heating.