Silicon wafers implanted with 30 keV He ions at room temperature in a low pressure hydrocarbon atmosphere exhibited visible photoluminescence. The samples were characterized by Raman, infrared, transmission electron microscopy, and heavy ion elastic recoil detection analysis. Two different layers were distinguishable on top of the silicon, with the upper layer comprising mostly amorphous carbon, as confirmed on a similarly implanted Be sample. Green photoluminescence was found to arise from the thinnera‐Si1−xCx:H interface layer. Such a buried intermixed layer could be incorporated into a stable visible light emitting device based on crystalline silicon. ©1995 American Institute of Physics.