Theoretical Study of Chlorine for Silicon Nanocrystals

In the framework of density functional theory we show that a chlorine (Cl) atom prefers residing at the surface of silicon nanocrystals (Si NCs) in single coordination, passivating a Si atom. The surface of Si NCs is covered by H in a very Cl-poor environment, while it may be covered by both H and Cl in a less Cl-poor environment. The Cl coverage increases with the increase of the chemical potential of Cl. At rather high Cl coverage the NC structure is distorted. The band-edge recombination rates of Cl-passivated Si NCs may be significantly larger than that of completely H-passivated ones.