Impact of Ni co-implantation on Si nanocrystals formation and luminescence

Abstract

We investigate the Si nanocrystals (Si-nc) growth and photoluminescence (PL) obtained by Si and Ni co-implantation. After 1h of annealing at 1000°C, PL emission between 600 and 1000nm is observed to be five times higher for samples containing 0.04–0.21at.% Ni than for samples without Ni. For samples annealed at 1100°C, a small increase in PL intensity is observed followed by a decrease for Ni contents above 0.3at.%. Our results are well described by a simple model which assumes that Ni atoms act both as a nucleation center for amorphous Si (a-Si) clusters crystallisation and as a non-radiative recombination site when more than one atom is included in a Si-nc. The nucleation effect is supported by the increase in PL intensity, the increase of PL decay time and the decrease of the a-Si Raman peak intensity at 480cm−1 for samples annealed at 1000°C in presence of ∼0.1at.% Ni. Time-resolved PL shows that Ni mainly affects two emission bands. The first band, around 730nm, is related to an oxygen surface state, suggesting that Ni enhances oxygen bonding with Si-nc. The second band, around 880nm, is associated to the crystallisation effect induced by Ni at lower annealing temperature.