AVS 51st International Symposium
    Surface Science Wednesday Sessions
       Session SS2-WeM

Paper SS2-WeM1
Atomic Structure Determination of @beta@-SiC(001)-(3x2): Experiment and Calculations

Wednesday, November 17, 2004, 8:20 am, Room 210C

Session: Semiconductor Surface and Interface Structure
Presenter: E.G. Michel, Univ. Autonoma de Madrid, Spain
Authors: A. Tejeda, Universidad Autonoma de Madrid, Spain
D. Dunham, Northern Illinois Univ.
F.J. Garcia de Abajo, CSIC-UPV/EHU and DIPC, Spain
J.D. Denlinger, Ernest Orlando Lawrence Berkeley National Lab
E. Rotenberg, Ernest Orlando Lawrence Berkeley National Lab
E.G. Michel, Univ. Autonoma de Madrid, Spain
P. Soukiassian, Commissariat a l'Energie Atomique and Northern Illinois Univ.
Correspondent: Click to Email
Silicon carbide is a IV-IV compound wide band-gap semiconductor with multiple technological applications. The structure of the Si-rich 3C-SiC(001)-(3x2) surface reconstruction is determined using soft x-ray photoelectron diffraction. Photoelectrons are detected along a full hemispherical sector for different photon energies. The experimental intensity modulations were compared in this work with the results of a suitable scattering formalism that simulates the measured PED by modeling the structure of the last atomic layers. A spherical-wave multiple-scattering cluster formalism was used to reproduce the data and discern the correct surface structure of Si-rich 3C-SiC(001)-(3x2), obtained from a systematic search between the models proposed in the literature. The favored model is a modified version of the two-adlayer asymmetric dimer model (TAADM). An R-factor analysis has been employed to refine this model. We determine the interlayer spacings of the last six atomic layers and find a corrugation of 0.25 Å for the atoms in the outermost dimer. Atoms in the layer underneath dimerize as well, with alternating long and short bond lengths. The long-and-short alternateness between dimer bond lengths explains the top dimmer asymmetry along one single direction. The dimerization takes place through lateral relaxation, without large vertical distortions. The third atomic layer is also dimerized, with a dimer bond length of 2.43 Å. We conclude our results, together with STM and GIXRD experiments, converge in a unifying model for the 3C-SiC(001)-(3x2) surface.