Structural Modifications in Amorphous Ge Produced by Ion Implantation

Abstract Raman spectroscopy was used to analyze structural modifications of monocrystalline Ge implanted with 3×10 12 to 3×10 16 cm −2 74 Ge ions, at either room temperature (RT) or liquid nitrogen (LN) temperature. In all implanted samples, beyond the amorphization threshold dose (≃10 14 cm −2 ), a dose-dependent evolution of the amorphous matrix could be followed. However, changes induced in samples implanted at −196°C (LN) differed from those implanted at 21°C. Characteristic Raman parameters relevant for disorder assessment suggest relaxation of the amorphous network with ion dose in samples implanted at RT in contrast to the LN temperature samples, in which additional implantation produces further disordering. These findings are consistent with the results obtained by extended X-ray absorption fine structure spectroscopy (EXAFS) wherein again both a dose- and temperature-dependent evolution of the inter-atomic distance distribution was observed.