Fabrication and characterization of heterojunction made of porous silicon and polyaniline synthesized by chemical and electrochemical routes

Abstract

Polyaniline (PANI) samples were deposited through chemical and electrochemical routes onto macroporous silicon (MPS). Their chemical and electrical features were investigated. For this, Fourier transforms infrared, Raman, and energy dispersive spectroscopies were used to show the successful incorporation of PANI into the pores and the formation of silicon oxide as a consequence of the silicon instability in the aqueous solution. The electrical parameters extracted by fitting the current-potential curves using the thermionic emission model of two opposite diodes being one at the PANI/MPS interface and the other at the silicon/back contact, indicate a Schottky barrier of about 0.730 V at the first interface and between 0.795–0.840 V at the second one and becomes more significant in the measurements between two contacts at the PANI surface. The chemical analysis reveals the presence of silicon oxide in both structures. This compound was found to be the determining factor for changing the electrical behavior. A larger flat band was measured in the device made by the chemical synthesis of PANI. The impedance analysis has shown that charge transfer is determined not only by the PANI and silicon oxide conductivity but also by the depletion layer's electrical features. However, the differential activation energy analysis indicates that PANI is chemically deposited, and the charge transport occurs hopping conduction. In contrast, in the electrochemically one, the charge is through impurity band conduction.