Formation of Porous Silicon Nanostructures in NH4F/C3H8O3 Solution

Abstract

Nanostructured porous silicon layer were successfully formed by an anodization method in viscous electrolyte containing glycerol and NH4F solution. P-type (100) silicon wafers were anodized with various anodizing times (1-8 h), NH4F concentrations (0.5-3 M) and applied voltages (10-30 V). The current density characteristic during anodizing and the morphology of porous silicon were measured using data acquisition loggers and field emission electron microscope (FE-SEM), respectively. The anodized surface produced high surface roughness and showed two types of porous structures consisting of macropores (macro-PSi) and mesopores (meso-PSi). The meso-Psi located in the macro-PSi structures. The size of macro-PSi increased with the increase of anodization time, the decrease of NH4F concentration and the decrease of applied voltage. The average diameter and depth of macro-PSi varied from 0.34 to 1.40 μm and 54 to 446 nm, respectively. For the meso-PSi, this method can produce an average diameter and thickness of mesopores in the range of 19-33 nm and 52-157 nm, respectively.