AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS1-WeM

Paper SS1-WeM4
Step-Step Interactions on TaC(910)@footnote 1@

Wednesday, October 27, 1999, 9:20 am, Room 606

Session: Surface Structure
Presenter: J.F. Wendelken, Oak Ridge National Laboratory
Authors: J.-K. Zuo, Oak Ridge National Laboratory and Southwest Missouri State University
T.-J. Zhang, University of Tennessee and Oak Ridge National Laboratory
J.F. Wendelken, Oak Ridge National Laboratory
Z. Zhang, Oak Ridge National Laboratory
D.M. Zehner, Oak Ridge National Laboratory
Correspondent: Click to Email
TaC, an ionic crystal with an extremely high melting point of ~3983 C, exhibits a strong faceting behavior for (n10) surfaces after heating to ~2000°C.@footnote 2@ These facets are very regular when n = 1, 2 or 3 but become less regular when n = 9. Through a scanning tunneling microscopy based study of the step distribution and structure on TaC(910), we determine that the observed morphology results from the interplay of a step-step repulsive interaction with both short- and long-range attractive interactions. The surface is dominated by bunched double-height steps where the bunches are separated by relatively long intervening (100) terraces having irregular widths. The step-separation distribution is highly skewed and sharply peaked at 13 atomic rows, the average spacing within a step bunch, while the (910) orientation is maintained with an average step-separation of about 18 rows. A Monte Carlo simulation shows that a weak, long-range, attractive interaction, -B/x@super a@, must be added to a strong, medium-range, repulsive interaction, A/x@super 2@, to fit the measured distribution. In addition, a short range attractive interaction is required for the creation of multiple-height steps that are oriented in the [010] direction. Possible physical origins for each of these interactions will be discussed. @FootnoteText@ @footnote 1@ ORNL is managed by Lockheed Martin Energy Research Corp. under U.S. DOE Contract No. DE-AC05-96OR22464. @footnote 2@ J.-K. Zuo, J. M. Carpinnelli, D. M. Zehner and J. F. Wendelken, Phys. Rev. 53, 16013 (1996).