Topographical changes of thin copper wires (chemical purity 99.9%, 30–50 μm in diameter) during 20 keV argon ion bombardment up to 4 × 1019 ions cm−2 at several temperatures between room temperature and 1073 K have been studied using the Scanning Electron Microscope. It is observed that there is a notable difference in the surface topography of copper wires below 423 K and above 573 K. This experimental observation is related to the diffusion of metal atoms in near-surface layers of samples.