Direct observation of individual nanometer-sized light-emitting structures on porous silicon surfaces

Abstract

We present the first observations of nanometer resolution mapping of visible-light emission from 85% porous silicon. Using an STM tip as a local source of electrons to excite cathodoluminescence, simultaneous topographic and light intensity profiles are reported. The photon maps reveal contrast in emission intensity on a scale relevant to the proposed dimensions of the luminescence process (-4nm). We suggest that excitation of individual quantum confinement structures has been observed. The technique overcomes the wide disparity in length scales of the photons ((600÷ 900) nm) and the characteristic size of the origins of the luminescence ((1 ÷ 5) nm) which have precluded previous experimental correlations of structural and luminescent behaviour. © 1993 IOP Pubilishing Ltd.