AVS 46th International Symposium
    Surface Science Division Monday Sessions
       Session SS1+EM-MoA

Paper SS1+EM-MoA9
Cu Interaction with Al@sub 2@O@sub 3@ Substrates: Effects of Defects and Coverage

Monday, October 25, 1999, 4:40 pm, Room 606

Session: Metals on Oxides
Presenter: J.A. Kelber, University of North Texas
Authors: C. Niu, University of North Texas
K. Shepherd, University of North Texas
J.A. Kelber, University of North Texas
Correspondent: Click to Email
We report UHV surface science studies of the wetting and nucleation behavior of Cu on sapphire(0001). Such fundamental wetting and nucleation interactions are of increasing importance in microelectronics, joining and brazing, as well as in catalysis. This study focuses on the effects of defects and kinetic factors for well-defined systems that are critical to an understanding of behavior for "real world" systems. On clean sapphire, Cu is initially present as Cu(I) to a coverage of 0.35 ML [ML = monolayer], after which a second, metallic Cu layer begins to grow. This behavior is in agreement with recent theoretical calculations by A. Bogicevic and D. R. Jennison[Phys. Rev. B (in press)]. The behavior of Cu on sapphire at elevated temperatures is coverage dependent. For @theta@@sub Cu@ < 0.35 ML, Cu(I) remains stable on the surface for temperatures up to ~ 1000K. However, in the presence of Cu(0), e.g. @theta@@sub Cu@ = 0.75 ML, Cu(I) reacts to form additional Cu(0) at about 500K. Pre-sputtering of the sapphire surface prior to Cu deposition inhibits Cu(I) formation and enhances Cu(0) formation at low coverage, correlating with the sputter-induced dehydroxylation of the sapphire surface and creation of oxygen vacancies. These data indicate that variations of a small number of surface defect densities can explain the large number of contradictory results obtained for the Cu/alumina systems. The significance of these findings to "real world" applications (e.g. Cu on oxidized Ta and other microelectronics diffusion barriers) will be discussed.