Corrosion, Passivation, and the Effect of Water Addition on an n-GaAs(100)/Methanol Photoelectrochemical Cell

A combination of picosecond photoluminescence and electrochemical studies reveals information about the GaAs/methanol interface. The electrochemistry occurring at the solid/nonaqueous liquid junction is found to have a strong influence on the observed photoluminescence as seen by photoluminescence vs voltage (PL− V ) scans and by trends in the time-resolved photoluminescence decays. The effect of corrosion of the cell on the PL− V profile is examined in detail. It is found that the inclusion of the redox couple gives some protection from corrosion, but the addition of a small amount of water to the nonaqueous cell gives even more. Further water additions lead the cell back to a state that is conducive to corrosion and eventually leads to Fermi level pinning of the GaAs.