Creation of surface and bulk defects of germanium and surface roughening of germanium during high energy ion irradiation

The formation of nanocavities depends strongly on temperature since the formation of nanocavities depends on kinetics of bulk point defects (vacancies and interstitials) produced by ion irradiation. More nanocavities are formed deeper inside the Ge crystal at 500°C compared to 400°C, while much smaller number of nanocavities are formed at 600°C. Due to the low mobility of bulk point defects at 400°C, not all the implanted Xe atoms are contained in the observed nanocavities, while probably almost all the implanted Xe atoms are contained in the nanocavities at 500°C. At 600°C, the areal density of implanted Xe atoms is small and no Xe peak is detected by RBS due to the high mobility of bulk point defects and Xe atoms.; Large pits, which are more than several bilayers deep, are formed on Ge even when less than a bilayer of surface material is removed. The number of large pits initially increases and then decreases with increasing ion fluence, and even 650 eV Xe ions can create large pits on Ge. Large pits are formed on Ge due to the annihilation of nanocavities on the Ge surface by the interaction of displacement cascades of keV Xe ions with nanocavities. 20 keV Xe ions can create small pits on Ge(111), which are more than a bilayer deep, as well as large pits. The creation of small pits is due to surface damage creation process by single 20 keV Xe ions.; Surface patterns of valleys and mounds are observed at 250°C and 275°C due to the asymmetric kinetics of surface vacancies at step edges, while no surface pattern formation is observed at room temperature. Also, model of Politi and Villain agrees relatively well with the roughening and coarsening of the Ge(111) surfaces etched by 5 keV Xe ions at 250°C and 275°C. At 300°C, a surface pattern is observed only when the incident ion direction is parallel to the step direction; this surface pattern is the ripple morphology produced by curvature dependent sputtering yield.