Complementary infrared and transmission electron microscopy studies of the effect of high temperature–high pressure treatments on oxygen-related defects in irradiated silicon

Abstract

Czochralski-grown silicon samples subjected to high temperature–high pressure (HTHP) treatments in the range of 900 °C were irradiated with fast neutrons. Transmission electron microscopy measurements revealed the presence of oxygen precipitates (SiOx) and dislocation loops. The purpose of this work is to investigate the effect of these defects on the annealing behavior of neutron-irradiated induced oxygen-related defects, mainly the VO and the VO2 centers. To this end, infrared spectroscopy measurements were employed to monitor the conversion of the VO center (828 cm−1) to the VO2 center (890 cm−1 band) during isochronal anneals. In the untreated samples this conversion occurs around 300 °C. In our studies, we found that the annealing temperature (Tann) of the VO centers is lower than 300 °C. The value of Tann depends on the particular HTHP pretreatment. Actually, as a result of the precipitation process silicon self-interstitials (SiIs) are emitted and a number of them is bound at the Si/SiOx interface. This region acts as a source of SiIs and upon their liberation the reaction VO+SiI→Oi is activated. The temperature at which this reaction becomes significant depends on the degree of binding of the SiIs at the interface and the number of the SiIs available to participate, which in turn depend on the particular HTHP pretreatment. Thus, if the reaction VO+SiI→Oi, precedes the reaction VO+Oi→VO2, the Tann of the VO defect will be determined mainly by the former reaction.