Long-persistent luminescence in near-ultraviolet from silicon nanowires

Silicon-rich nanowires with persistent near-ultraviolet luminescence were fabricated with thermal evaporation of silicon monoxide (SiO) powder at 1350 K. They contain quantum-confined elemental silicon structures of the order of nm dimension, and are capped by silicon oxide. The samples exhibit orderly color distribution along the direction of the carrier gas flow. When excited with the 280 nm light, the samples emit broad photoluminescence band from 330 to 470 nm with a long afterglow of more than 10 s, and the color shifts from near-ultraviolet to blue and green gradually. The morphology dependent luminescence might be attributed to the emission from the quantum-confined silicon crystallites of various sizes embedded in the oxide layer, and near surface states in the nanowires.