STM investigation of gallium single-crystal surfaces close to bulk melting

Abstract

We have used STM to investigate single-crystal Ga surfaces oriented along all major symmetry directions up to the bulk melting temperature Tm = 29.78°C. The single-indexed surface orientations (001), (010) and (100) were remarkably stable up to Tm. Neither surface diffusion nor step mobility were observed in STM images measured up to the onset of bulk melting. Thermally assisted disordering below Tm was not detected on any of these single-indexed surfaces. As bulk melting set in, irregularly shaped hillocks up to a micrometer in size appeared on the otherwise undistorted atomically flat surface. The rather densely packed (111) surface was much less stable upon imaging with the STM and became increasingly susceptible to tip-induced surface modifications as the temperature approached Tm. On the loosely packed (110) surface, a reversible structural transition to a higher packing density and partial disordering was detected 0.5 K below Tm. In addition, both the formation of a dislocation and defect dynamics were observed on the (110) surface. © 1992.