Abstract:
Metglass MG2705M foils of about 17 m thickness were irradiated at 90 K by
130 MeV 28Si ions, up to a fluence of 1:154 1016 ions cm−2. The surface modifications induced
by irradiation have been examined by scanning electron microscopy (SEM) and scanning tunnelling
microscopy (STM). It has been observed that smoothing of the sample surface is evident in both
SEM and STM micrographs. The SEM pictures show a decrease in the heights of the ‘hills’ and
filling up of the ‘valleys’ on micrometre length scales. The STM pictures, on the other hand, show
smoothing of scratchlike surface disorders at nanometre length scales. However, the electronic
energy loss Se, of 5:75 keV nm−1, does not lead to detectable track diameters, in agreement with
the existing results. The observations have been attributed to a large electronic energy deposition
due to high fluence, and a subsequent local shear relaxation of the near surface atoms. The theory
of shear flow mechanism has been extended further to explain the results.
