SSL Seminar Series 2002 No.5
Title: New Results on SiC(0001) Surface Obtained using RHEED.
Speaker: Dr Nikilai Yakovlev(IMRE)
Date: May 23, 2002
Time: 5:00-6:00pm
Venue: Physics Conference Room (Blk S13 M01-15)

Abstract:
RHEED is reflection high energy electron diffraction. Analysis of atomic structure of the surface is done measuring RHEED rocking curves, that are dependences of diffracted intensity on the incident angle, and comparing them with calculated curves. In the present study, the data were measured at the Department of Chemistry, NUS, and the calculations were done at the University of Leicester using dynamical theory [1] developed there. To fit the rocking curves, the Marquardt algorithm of adjusting atomic positions [2] was used. For roo3*root3 superstructure on SIC(0001) surface, RHEED gave evidence of incomplete coverage of Si adatoms. In the discussion, this result is correlated with existence of this superstructure at high temperature. For 3*3 superstructure, RHEED data agree with the model of one tetra-cluster per unit cell, however its twist in our results is smaller than that obtained from density functional calculations. We discuss the role of impurities in this discrepancy.

[1] P.A.Maksym, J.L.Beeby, Surf.Sci. v.110, 423 (1981), v.140, 77 (1984)
[2] U.Korte, G.Meyer-Ehmsen, Surf.Sci. v.271, 616 (1992)