Observation of the Surface of Cyclically Deformed Au by Scanning Tunneling Microscope

Abstract

Surface topography of a cyclically deformed thin Au plate was observed using a scanning tunneling microscope (STM). Observation was made on the specimens subjected to alternating pure bending with a total strain amplitude of 0.2, 0.1 or 0.05% for various numbers of cycles. The surface became proportionately rough as the number of cycles increased. Heights of the hills and valleys were increased as the number of cycles increased, and they were 20 to 30 nm at most, irrespective of the strain amplitude. However, the average spacing between the hills and valleys became shortened as the strain amplitude increased. At least two slip systems had to be operated for the formation of these rough surfaces. Nucleation of microcracks resulted from concentrated deformation at some of the hills and valleys. Heights of hills and valleys adjacent to the grain boundary were much larger than those inside the grains.