[Stabilising porous silicon luminescence by a novel titanium-doped stain etching approach]

Porous silicon (PS) with good luminescent stability and homogeneity was fabricated by using a novel titanium-doped stain etching approach. The blue shift and degrading of the photoluminescence (PL) were not observed when stored and annealed in ambient air. The good luminescent stability is attributed to the surface passivation of the PS by both oxygen and titanium during fabrication. The PL position is independent of the etching time. The results indicate that the photon excitation process meets the quantum confinement mechanism since the PL intensity reaches its maximum when the particle size-dependent band gap is in resonance with the exciting photon energy. The photon emission process is, however, not a direct band-band transition, rather through a surface state within the band gap, instead.