Intense and stable blue-violet emission from porous silicon modified with alkyls

An intense blue-violet band, centered at 3.0 eV, has been observed besides the red-orange band of the photoluminescence (PL) from the chemically modif ied porous silicon (PS) samples. The PS samples were formed on 30-50 Ohm cm p-type (100) Si wafers by anodic etching at large current densities and th en treated with 5-cyano-1-pentynes in toluene solution at 110-120 degrees C . The intensities of the blue-violet lights increase with the increasing of the etching current densities, while the peak energies are hardly changed. The Fourier transform infrared spectra of the modified samples show that t he alkyls have been bonded to the surfaces of the nanometer crystallite sil icon particles. The decays of the blue-violet emission with a lifetime abou t 0.5 mu s are different from the nanosecond lifetimes of the blue emission s in the oxidized PS samples reported before, and the 20 mu s lifetimes of the concomitant orange PL bands. A carbon-compounds-related luminescence ce nter has been proposed as the origin of this blue-violet PL band. (C) 2000 American Institute of Physics. [S0021-8979(00)01920-4].