X-ray reflectivity investigation of thin p-type porous silicon layers

X-ray reflectivity (XRR) was used to investigate the p(-)- and p(+)-type po rous silicon (PS) layers. For p(-)-type samples, a linear dependence of the thickness versus the anodization time was revealed in the 10-250 nm thickn ess range for even very short etching times and the layer structure was hom ogeneous with a transition layer at the PS/substrate interface. For p(+)-ty pe materials, a surface film was unexpectedly observed for layers of low po rosity. The structure and origin of this surface film is discussed in this article. (C) 1998 Elsevier Science Ltd. All rights reserved.