GENERATION OF NANOSIZED GROOVES AND HOLES ON METAL-SURFACES BY LOW-TEMPERATURE ELECTRON-IRRADIATION

This paper reports a novel phenomenon in surface physics, namely the f ormation of aligned nanogrooves and deep nanoholes on the exit surface of thin (001) gold foils irradiated with high doses of 360, 800 and 1 250 keV electrons at temperatures of about 100 K. The grooves and hole s, with widths between about 1 and 2 nm, appear to be the smallest so far produced in metals. The formation of the nanogrooves depends on th e irradiation direction: irradiation along [001] produces grooves exte nding along [100] and [010], irradiation along [011] gives grooves alo ng [100], whereas no marked grooves have been observed for [111] irrad iations. By contrast, nanoholes, which may reach depths exceeding 20 n m, develop mainly along the beam direction. At room temperature the na noholes transform into voids of larger diameters. There is strong evid ence that the formation of the groove pattern is a self-organized proc ess. A tentative mechanism involving symmetry breaking by strongly ani sotropic surface collision sequences is proposed.