No abstract

A tuning of the nanocrystal sizes in porous silicon has been obtained by self-ion implantation in p-type silicon wafers before the anodization treatment. Sample porosity, luminescence spectra, Raman scattering, and transmission electron microscopy have been used to determine the structure of porous silicon samples. A porosity increase, a blue shift of the luminescence peak, a widening of the phonon resonance, and a decrease in the size features revealed by transmission electron microscopy (TEM) images are observed by increasing the ion implantation dose. It is suggested that this effect results from the increased resistivity of the Si wafer caused by the ion implantation damage.

The room temperature current/voltage (I–V) characteristics of several porous silicon(PS)/metal diodes are measured. Different metals are used to form the contacts. Severe stress is also applied to the diodes and the I–V characteristics of stressed diodes are analysed. The present study supports the description of Ben Chorin et al. of these diodes, where the rectifying junction is placed at the interface between the PS layer and the bulk Si and the carrier transport through the PS layer is determined by a hopping mechanism.

Luminescence at an energy higher than the Si band-gap energy has been observed following H implantation and annealing treatments of Si samples. This phenomenon is discussed considering the damage caused by the H implantation and its evolution with thermal treatments. No definitive answer on the origin of the luminescence is given but various possible models are proposed.