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.