Hydrogenated Silicon Nanoparticles Relaxed in Excited States

Abstract

Small hydrogenated silicon particles with diameters smaller than 2 nm were geometrically relaxed in excited states using density functional tight-binding methods. The relaxation caused Stokes shifts and optical-absorption spectrum red shifts with the particle size increases, consistent with experimental observation. Interestingly, the emission energies were fluctuated around 1.51−3.25 eV for small-size particles with diameter smaller than 1.5 nm (≤Si87H76), and became inversely proportional to the size at larger diameters. The electronic property changes due to quantum confinement effects and significant structural deformations were shown to be responsible for the above-described features of the small silicon nanoparticles.