| AVS 57th International Symposium & Exhibition | |
| Surface Science | Monday Sessions |
| Session SS2+EM-MoM |
| Session: | Semiconductor Surfaces and Interfaces |
| Presenter: | J.S. Becker, University of Chicago |
| Authors: | J.S. Becker, University of Chicago R.D. Brown, University of Chicago E. Johansson, California Institute of Technology N.S. Lewis, California Institute of Technology S.J. Sibener, University of Chicago |
| Correspondent: | Click to Email |
The surface structure and vibrational dynamics of CH3–Si(111) and CD3–Si(111) surfaces were measured using helium atom diffraction. The elastic diffraction patterns exhibited a lattice constant of 3.82 Å, in accordance with the spacing of the silicon underlayer. The high quality of the observed diffraction patterns indicates a high degree of long-range ordering for this novel interface. The vibrational dynamics were investigated by measurement of the Debye-Waller decay of the elastic diffraction peaks as the surface temperature was increased. The angular dependence of the specular (θi = θf) decay revealed perpendicular mean-square displacements and He-surface well depths of 1.0·10-5 Å2 K-1 and 7.5 meV for the CH3–Si(111) surface and 1.2·10-5 Å2 K-1 and 6.0 meV for the CD3–Si(111) surface. Effective surface Debye temperatures of 983 K for CH3 and 824 K for CD3 were calculated. These unusually large Debye temperatures suggest that collisional energy accommodation at the surface occurs primarily through Si-C local mode. The parallel mean-square displacements were 4.3·10-4 Å2 K-1 and 4.5·10-4 Å2 K-1 for CH3– and CD3–Si(111) surfaces, respectively. The increase in thermal motion is consistent with interaction between the helium atoms and Si-CH3 bending modes. These experiments yield new information on the dynamical properties of these robust and technologically interesting semiconductor interfaces.