Effect of Electrolyte Concentration on Anodic Nanoporous Layer Growth for n-InP in Aqueous KOH

Abstract

The surface morphology and sub-surface porous structure of (100) n-InP following anodization in 1 - 10 mol / l aqueous KOH were studied using linear sweep voltammetry (LSV) in combination with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was observed that the pore width increased and the inter-pore spacing decreased with decreasing concentration and that the porous layer depth also varied reaching a maximum thickness at ~2.2 mol / l. It is proposed that preferential pore propagation occurs along <111> directions, contrary to previous suggestions, and that the resulting nanoporous domains, initially formed, have triangular cross-sections when viewed in one of the {110} cleavage planes, 'dove-tail' cross-sections viewed in the orthogonal {110} cleavage plane and square profiles when viewed in the (100) plane of the electrode surface.