Study of Porous Silicon Fabricated by Pulsed Anodic Etching of n-Si(100)

It is well known that porous silicon (PS) has a large range of morphologies. A pulsed anodic etching method is developed to fabricate uniform PS with different surface morphologies. Changes of PS on n-type Si surface after anodization with pulsed current with varying delay time were studied by scanning electron microscopy (SEM) and Raman spectroscopy. The SEM images show that a uniform and well defined silicon columns can be obtained with a correct choice of delay time. Raman scattering from the optical phonon in PS showed redshift of the phonon frequency, broadening and increased asymmetry of the Raman mode on decreasing delay time. Using the phonon confinement model, the average diameter of Si nano- crystallites has been estimated as 2, 2.6, 3, and 3.4 nm for delay time of 12, 25, 50, and 75 msec respectively.