Electrochemical effects in metal1 – a-Si:H – metal2 structures

Abstract

In the course of studying microwave plasma-deposited a-Si:H, some M1 – a-Si:H – M2 structures (where M1, and M2 represent dissimilar metals) exhibited a behavior similar to that of galvanic cells. For many pairs of metallic electrodes we have observed, in the dark, an open-circuit voltage (Voc) and a short-circuit current (Isc) that were stable over a period of several months. Such effects have been variously reported for M1–polymer–M2 cells, where no doubt remains as to their electrochemical origin. We describe here the observed phenomena, along with results from chemical profiling (elastic recoil detection analysis and Auger electron spectroscopy) studies, aging characterization by Fourier transform infrared spectroscopy, morphological studies by scanning transmission electron microscopy, low-frequency permittivity measurements, and I–V behavior in the dark and under illumination, and we interpret these results in terms of electrochemical reactions.