Effect of boron ion implantation and subsequent anneals on the properties of Si nanocrystals

Abstract

To study the effect of implantation of 1013–1016 cm−2 of boron ions and subsequent steady-state thermal or pulsed (20 ns) laser anneals on the properties of Si nanocrystals in SiO2, methods of photoluminescence and Raman scattering are used. Implantation of B ions quenched the photoluminescence caused by dimensional quantization. A comparison with the effect of other ions shows that an increase in the mass of incident particles leads to an increase in the contribution of elastic losses to the photoluminescence quenching. This circumstance is accounted for by the binding of the generated defects into complexes that are not the center of nonradiative recombination. Our studies confirmed the promotion of crystallization of nanoprecipitates as a result of the introduction of an impurity and also revealed special features related to the small size of boron atoms. It is shown that the postimplantation laser-induced anneals are efficient methods for recovering photoluminescence; this efficiency is caused by the possible short-term melting of nanocrystals. Notwithstanding the evidence indicating that boron enters the nanocrystals, there is no indication that free holes appear. It is believed that this phenomenon is caused by the fact that the depth of impurity levels is larger in nanocrystals.