AVS 51st International Symposium
    Surface Science Monday Sessions
       Session SS-MoP

Paper SS-MoP37
Measurement of Gibbs Free Energies of Surfaces in Vacuum, and their Use to Explain the Pressure Dependence of the Thickness of a Lead-Oxide Film

Monday, November 15, 2004, 5:00 pm, Room Exhibit Hall B

Session: Poster Session
Presenter: A.J. Slavin, Trent University, Canada
Authors: L. Bouzidi, Trent University, Canada
A.J. Slavin, Trent University, Canada
Correspondent: Click to Email
A method has been developed, using a high-stability quartz-crystal microbalance (HS-QCM)@footnote 1@, for determining the difference between Gibbs free energies of different surface oxide phases in ultrahigh vacuum. This is the only technique capable of such measurements, to our knowledge. These measurements have been used to explain the dependence, on oxygen pressure, of the thickness of a lead-oxide film grown on a gold substrate. The HS-QCM has also been used to measure a Pb:O ratio of 1:1, suggesting PbO as the surface oxide. Only the surface Pb monolayer oxidizes at an O@sub 2@ pressure of 5 x 10@super -6@ torr, with 1 x 10@super -4@ torr required to oxidize a second layer. For large Pb deposits on Au only the top two layers are oxidized up to an oxygen pressure of 10@super -2@ torr, apparently due to kinetic limitations. These results are quite different from the oxidation of pure Pb. @FootnoteText@ @footnote 1@ L. Bouzidi, S.S. Narine, K.G. Stefanov and A. J. Slavin; Rev. Sci. Instrum. 74, 3039-3044 (2003). .