X-RAY EXCITED OPTICAL LUMINESCENCE (XEOL) STUDY OF POROUS SILICON

It has been postulated that light emission from porous silicon is caused by quantum confinement of the electron states within silicon wires formed by anodic electroetching of silicon. In order to investigate this hypothesis we have made measurements of the X-ray excited optical luminescence (XEOL) and the total electron yield (TEY) as a function of X-ray energy for porous silicon at station 3.4 of the SRS at Daresbury laboratory. Results have shown that the luminescence is associated with elemental silicon, and this is true for as prepared and oxidised material. In the latter case the XEOL spectrum is completely different from the TEY. However, by considering the microscopic origin of the excitation together with time-dependent relaxation data, we conclude that the emission comes from silicon surface states and not quantum effects in the nanoparticles. This is in contrast to other similar studies