Amorphisation and surface morphology development at low-energy ion milling

Amorphisation and surface morphology development of Si and GaAs was studied by means of XTEM after ion bombarding at various low energies in our novel ion milling unit. In this device, the specimen is rotated and the ion energy can be reduced down to 0.12 keV. It was shown that the thickness of the amorphised layer is about 1 nm for Si/0.25 keV, and not observed for GaAs/0.25 keV and Si/0.12 keV. This amorphisation is much thinner than those measured at higher energies, e.g. 5 nm, 2.1 nm for Si/3 keV, GaAs/1.6 keV. Dynamic TRIM simulation could be successfully applied for the description of amorphisation. It will be shown for the first time that the interface roughness also decreases with decreasing ion energy.