The pivotal role of SiO formation in the migration and Ostwald ripening of Ge quantum dots

摘要

We report a unique, cooperative mechanism that involves the interplay of Ge, Si, and Oxygen interstitials enabling an unusual Ostwald ripening and migration behavior of Ge nanocrystallites and quantum dots (QDs) embedded within a SiO_2 matrix. In the presence of high Si interstitial fluxes with no supply of oxygen interstitials, the oxide surrounding the Ge QDs is decomposed by the Si interstitials, creating the volatile SiO reaction product and hence voids that enable the Ge QDs to grow by Ostwald ripening. When both Si and Oxygen interstitials are present in high concentrations, the Ostwald ripened Ge QD is further able to migrate towards the source of the Si interstitials. The QD movement occurs by virtue of the fact that the SiO created in front of the QD combines with O interstitials to regenerate SiO_2 behind the Ge QD on its migration path. Thus, SiO influences the migration and Ostwald ripening behavior of the Ge QDs via a unique "Destruction-Construction" mechanism.