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Title: Effects of O2 dissociation on a porous platinum coating in the thermal oxidation of GaAs
Authors: Hultquist, G.
Graham, M.J.
Wee, A.T.S. 
Liu, R. 
Sproule, G.I.
Dong, Q.
Anghel, C.
Issue Date: 2006
Citation: Hultquist, G., Graham, M.J., Wee, A.T.S., Liu, R., Sproule, G.I., Dong, Q., Anghel, C. (2006). Effects of O2 dissociation on a porous platinum coating in the thermal oxidation of GaAs. Journal of the Electrochemical Society 153 (2) : G182-G186. ScholarBank@NUS Repository.
Abstract: A 20-30-nm -thick porous Pt layer has been sputter-coated on a portion of a GaAs sample and subsequently the sample was oxidized at 500°C in O216 followed by O18 -enriched O2. The oxide formed was characterized by Auger electron spectroscopy, secondary ion mass spectrometry, and X-ray photoelectron spectroscopy, all with a lateral resolution of about 100 μm. Away from the Pt area, a mm-ranged gradually decreasing degree of As oxidation was observed in the outermost oxide layer. In the Pt area, Ga was preferentially oxidized at the oxide/substrate interface producing a five to seven times thicker oxide than in an area without the influence of Pt. A strongly enhanced dissociation rate of O2 on Pt particles and a subsequent O spillover to adjacent oxide explain the experimental observations. The mm-ranged spillover is believed to take place via fast lateral surface diffusion and results in the observed variation of oxidized As at the gas/oxide interface. In the Pt area, a high concentration gradient of dissociated oxygen across the oxide layer supplies a high flux of dissociated oxygen to the GaAs substrate where Ga is preferentially oxidized. The results clearly demonstrate that both a surface reaction and solid-state diffusion influence the oxidation rate. A localized high effective oxygen (O) activity that spills over to a nearby oxide area is believed to be a general phenomenon that is operating in oxides where a dissociating element such as Pt is present at O2 /oxide interfaces. © 2006 The Electrochemical Society.
Source Title: Journal of the Electrochemical Society
ISSN: 00134651
DOI: 10.1149/1.2150156
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