Measurement of porous silicon dielectric constant by VUV laser harmonic radiation

By combining the use of laser harmonic radiation as vacuum ultraviolet (VUV) light source with that of a standard NIR-VIS-UV spectrometer, the reflectance of porous silicon over a wide en ergy spectral range from 1 to 16 eV was measured. Reflected intensity modulation due to interference effects arising from the finite thickness of the porous layer in the visible range was also taken into account and reduced by fringe fitting. Porous silicon dielectric constant was then deduced from reflectance measurements by Kramers-Kronig analysis. Data are found to be in good agreement with those reported in literature, thus showing that laser harmonics represent a new alternative and suitable VUV source for optical characterisation of materials.