Combined surface analysis by synchrotron radiation photoemission spectroscopy and surface extended x-ray absorption fine structure of oxidation features of metal-deposited GaAs

Abstract

Synchrotron radiation photoemission spectroscopy (SRPES) was used to study the oxidation processes of metal-covered GaAs(100) surfaces in order to understand the catalytic effect of metal overlayers on the oxidation of GaAs with an eye towards possible practical applications. It is found that Au-covered GaAs surfaces show strongly enhanced oxidation rates compared to bare GaAs and Al- or Cu-deposited GaAs surfaces for unexcited oxygen exposure and dc plasma oxidation. From an analysis of the chemically shifted peaks, this enhancement effect is attributed to the formation of an interfacial AuGa alloy and free As. A sandwich structure of GaAs oxide/Au/GaAs is confirmed based on x-ray photoelectron spectroscopy, SRPES, and Auger electron spectroscopy in-depth profiling, while oxidation of Al/GaAs results in an Al oxide/GaAs oxide/GaAs structure. Furthermore, in situ analysis of heavily oxidized surfaces by a dc plasma using SRPES and surface extended x-ray absorption fine structure above the O K edge revealed that dc plasma oxidation results in heavily oxidized As2O5 with an oxygen double bond which may have some correlation to an ‘‘intermediate O 2p state’’ at binding energy (BE)=11 eV in the valence band.