Abstract
The electrochemical formation of a hybrid structure composed of a redox-active polypyrrole (PPy) and porous silicon (PSi) layer is demonstrated. PSi layers with pore sizes (similar to 200 nm) are prepared by the electrochemical anodization of n-type Si wafer in HF-based solution, whereas the PPy as a p-type conducting polymer was prepared by electro-oxidative polymerization of parent monomers in acetonitrile solution using PSi as a working electrode. Uniform and vertically-oriented PPy nanorod arrays were successfully fabricated inside the porous matrix. After pore filling, the electrical conductivity and photoluminescence of as-fabricated hybrid structure were remarkably enhanced. The PSi/PPy heterojunction was fully characterized by a variety of techniques including field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. Thermal properties were also evaluated using thermo-gravimetric analysis (TGA) measurements. Formation mechanism and surface properties of such hybrid structure along with its electrical and optical characteristics are addressed and thoroughly discussed. (C) 2014 Elsevier B.V. All rights reserved.