PREPARATION AND CHARACTERIZATION OF SURFACE-MODIFIED LUMINESCENT POROUS SILICON

Porous silicon layers are chemically grafted with trimethylsiloxy grou ps by exposure to hexamethyldisilazane (HMDS) vapors. After treatment, infrared spectroscopy reveals that part of the initially hydrogenated surface is actually modified. Luminescence of the porous layers appea rs to be little affected by the treatment. On strongly luminescent sam ples. the photocarriers exhibit the same infrared absorption as in hyd rogenated or oxidized porous silicon, evidencing the similar involveme nt of localized states in the luminescence process. The treated porous silicon layers also exhibit an increased stability against aging in a mbient, as compared to hydrogenated porous silicon. Furthermore, the m odification can be removed by simple exposure to HF vapor, thereby res toring the initial hydrogenated surface.