We explore the origin of visible photoluminescence in nanoscale silicon cones fabricated by reactive ion etching in silicon-on-insulator substrates utilizing rough silver films as masks. Photoluminescence (PL) visible to the naked eye was observed after oxidation and annealing. Samples oxidized at 900 degreesC exhibit intense yellow/green photoluminescence centered at about 530 nm. Samples oxidized at 1000 degreesC luminesce in the red-to-infrared region with peak positions between 650 and 730 nm. Transmission electron microscopy characterization is employed to show that PL at 530 nm can be understood in terms of defect states, while the PL at 650-730 nm can be explained by a combination of defect state and quantum confinement effects. (C) 2002 American Institute of Physics.