Regrowth of Ge with different degrees of damage under thermal and athermal treatment

Abstract

In this report, the recrystallization of pre-damaged Ge samples is extensively investigated under steady-state thermal annealing and ultrafast thermal spike-assisted annealing generated by high-energy ions. The (100) single-crystal Ge samples were pre-damaged using 100 keV Ar ion implantation. Three sets of pre-damaged Ge samples with sub-threshold (set A), threshold (set B) and above-threshold (set C) doses of amorphization, as estimated by Rutherford backscattering spectrometry in channeling mode (RBS/C), were suitably selected. Cross-sectional transmission electron microscopy (XTEM) images show distributed damaged pockets surrounded by crystalline material in the case of the as-damaged set A sample and completely damaged layer in the set C sample. These samples were used to study the regrowth of damage by (i) vacuum annealing at temperatures ranging from 373 K to 873 K for 30 minutes each and (ii) 100 MeV Ag ion irradiation-assisted annealing at four different temperatures: 100 K, 300 K, 373 K and 473 K. After 100 MeV Ag ion irradiation, set A samples have undergone complete recrystallization at 473 K. Similar recrystallization, but with lower magnitude, is also observed in the set B sample with increase in temperature. In set C samples, interestingly, nanowire formation was observed instead of recrystallization after irradiation at 100 K and 300 K, but recrystallization is observed at high-temperature irradiation, though it is much lower than those of set A and set B samples. The Arrhenius plot of the recrystallized fraction reveals a reduced activation energy of recrystallization by a substantial factor due to thermal spike-assisted recrystallization.