  Ion implantation has been a key technology for the controlled surface
modification of materials in microelectronics and generally, for tribology,
biocompatibility, corrosion resistance and many more. To form shallow junctions
in Ge is a challenging task. In this work the formation and accumulation of
shallow damage profiles was studied by in-situ spectroscopic ellipsometry (SE)
for the accurate tracking and evaluation of void and damage fractions in
crystalline Ge during implantation of 200-keV Sb ions with a total fluence up
to 1E16 cm-2 and an ion flux of 2.1E12 cm-2 s-1. The consecutive stages of
damage accumulation were identified using optical multi-layer models with
quantitative parameters of the thickness of modified layers as well as the
volume fractions of amorphized material and voids. The effective size of
damaged zones formed from ion tracks initiated by individual bombarding ions
can be estimated by numerical simulation compared with the dynamics of damage
profiles measured by ion beam analysis and ellipsometry. According to our
observations, the formation of initial partial disorder was followed by
complete amorphization and void formation occurring at the fluence of about
1E15 cm-2, leading to a high volume fraction of voids and a modified layer
thickness of approx. 200 nm by the end of the irradiation process. This agrees
with the results of numerical simulations and complementary scanning electron
microscopy (SEM) measurements. In addition, we found a quasi-periodic time
dependent behavior of amorphization and void formation represented by
alternating accelerations and decelerations of different reorganization
processes, respectively.
