TEMPERATURE-DEPENDENCE OF STEP DENSITY ON VICINAL PB(111)

The temperature dependence of step density on the vicinal Pb(lll) surf ace is investigated using reflection high-energy electron diffraction. When the temperature is increased from 323 to 590 K, the average terr ace width and the average string length at the step edge decrease from 85+/-25 to 37 +/- 16 Angstrom and from 220+/-33 to 25 +/- 8 Angstrom, respectively. Thermal step collapse on the Fb(lll) surface near its b ulk melting temperature is not observed. Above 530+/-7 K, the change i n the string length at the step edge with temperature becomes small, a nd the intensity of the (00) beam is significantly decreased. We concl ude that partial step melting at the step edge occurs at the surface a bove 530+/-7 K.