Photoelectrochemical characterization of p-type silicon electrodes covered with tunnelling nitride dielectric films

Abstract

The photoelectrochemical behaviour of p-Si(100) single crystal electrodes in aqueous solution, covered with a very thin nitride film, was studied. The silicon surface nitridation was achieved in a N 2–H 2 plasma at floating potential. The as-grown insulating Si 3N 4 layers, with thickness inferior to 3.1 nm, allow the electrons to tunnel in the presence of an electric field by the Fowler–Nordheim tunnelling mechanism. However, the p-Si(100)/Si 3N 4-electrolyte interface generated lower photocurrent densities than those generated by naked p-Si(100) electrodes. In contrast, the nitridated silicon surface displayed a significant stability improvement in aqueous electrolyte (neutral pH). An overvoltage higher than 0.6 V for water oxidation on a p-Si(100) covered with a 2.4 nm Si 3N 4 layer was measured. The results show that silicon covered with a nitridated thin film may be useful to stabilize electrodes in photoelectrochemical applications.