Effects of O-2 dissociation on a porous platinum coating in the thermal oxidation of GaAs
2006 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, Vol. 153, no 2, G182-G186 p.Article in journal (Refereed) Published
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 degrees C in O-16(2) followed by O-18-enriched O-2. 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 mu m. 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 O-2 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 O-2/oxide interfaces.
Place, publisher, year, edition, pages
2006. Vol. 153, no 2, G182-G186 p.
IdentifiersURN: urn:nbn:se:kth:diva-15370DOI: 10.1149/1.2150156ISI: 000234543400069ScopusID: 2-s2.0-30644472233OAI: oai:DiVA.org:kth-15370DiVA: diva2:333411
QC 201005252010-08-052010-08-05Bibliographically approved