Novel Ge nanopattern by heavy Bi monomer irradiation

Surface pattern on Ge induced by Bi cluster ions doffer drastically from morphology after monomer irradiation. Large aspect ratios of dots and ripples and crystalline surfaces after cluster irradiation have been observed. A novel patterning mechanism explains the dot formation qualitatively by means of local tiny melt pools induced by ion impact . Moreover this model predicts the formation of dot pattern even for monomer irradiation at elevated temperature. The aim of this work is to investigate the pattern formation by heavy Bi monomer bombardment. Surface pattern obtained at room temperature and under normal incidence are investigated in an ion energy range from 4 to 60 keV. A energy driven pattern transition from hole over dot to sponge like structures is observed. Moreover, the pattern formation by Bi monomer ions is investigated at elevated temperatures showing a energy dependent transition from sponge to dot like pattern.