Effect of Surface Chemistry on Quantum Confinement and Photoluminescence of Ammonia-Passivated Silicon Nanocrystals

Abstract

Silicon (Si) nanocrystals (NCs) less than 5 nm in diameter are grown on SiO2 surfaces using hot wire chemical vapor deposition, and the dangling bonds and the reconstructed bonds at the NC surface are passivated and transformed with D and NDx by using deuterated ammonia (ND3), which is predissociated over a hot filament. At low hot wire ND3 doses, photoluminescence (PL) emission is observed from a defect state at 1000 nm corresponding to reconstructed surface bonds capped by predominantly monodeuteride and Si-ND2 species. As the hot wire ND3 dose is increased, di- and trideuteride species form, and intense PL is observed around 800 nm, which does not shift with NC size and is associated with defect levels resulting from NDx insertion into the strained Si−Si bonds forming Si2═ND. A clean bandgap can be realized with fully relaxed and fully terminated NC surfaces consisting of di- and trideuterides and SiND2.