Macroporous silicon/polyaniline Schottky contacts: Fabrication and electrical characterization in air and liquid solution

Abstract

The chemical and electrical properties of polyaniline/macroporous silicon heterojunction were investigated. It was found that this device is constituted by pores with an effective diameter ranging from 0.4 to 1.3 μm and length from 1.3 to 4.5 μm as established by scanning electron microscopy, while Energy-dispersive X-ray and infrared spectroscopies reveal that during polyaniline synthesis silicon oxide grows at the pore surface walls. The electrical characterization through the current-potential and impedance measurements shows non-homogeneous polyaniline formation through the samples. The modeling of the current-potential curves was performed using the thermionic model where the ideality coefficient was assumed to be dependent on the applied potential, being higher for the Schottky junctions measured through two contacts on the polyaniline/macroporous silicon surface, which was attributed to the higher thickness of silicon oxide between the two contacts at this region, as suggested by the higher flat band potential obtained from the Mott-Schottky analysis. Analogous results were achieved through the impedance electrochemical measurements. The analysis in ethanol containing low amounts of naphthalene shown an almost linear relationship between the current intensity and the naphthalene concentration (or pH level of the solution). A comparable behavior was found by plotting impedance and phase shift versus naphthalene concentration.