CONTROL OF SILICON NANOCRYSTALLITE SHAPE ASYMMETRY AND ORIENTATION ANISOTROPY BY LIGHT-ASSISTED ANODIZATION

It is shown that the different and conflicting results on the strength of polarization memory effect on porous Si result from the influence of light on the electrochemical etching process. Illumination in gener al reduces the memory effect by decreasing the particle shape asymmetr y. Linearly polarized light can both enhance or reduce the effect. It is accompanied by an in-plane orientation anisotropy of the memory par ameter for (100) porous Si. This effect is evidence for a preferential alignment of the crystallite asymmetry axis normal to the light polar ization. (C) 1997 Institute of Physics.