Cathodoluminescence enhancement in porous silicon cracked in vacuum

An increase of the cathodoluminescence (CL) signal of porous silicon (PS) cracked in vacuum of up to three orders of magnitude has been achieved. Under high electron-beam currents, the samples cracked in interconnected pieces of tens of microns, exposing new surfaces to the electron beam. This treatment enhances the radiative intensity in PS associated with a broadband peaked at 720 nm, which is highly stable while the sample is kept in vacuum. Cross-sectional CL observations show that most of the light is generated in the top surface of the porous layer. The spectral depth dependence of the emitted light reveals a relatively weak blue emission in the region closer to the substrate.