AVS 45th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS1-TuM

Paper SS1-TuM2
Geometry, Energetics, and Electronic Structure of the Dimer Reconstruction on the Carbon, Silicon and Germanium (100) Surfaces

Tuesday, November 3, 1998, 8:40 am, Room 308

Session: Semiconductor Surface Structure
Presenter: H.C. Kang, National University of Singapore
Authors: H.C. Kang, National University of Singapore
C. Yang, National University of Singapore
Correspondent: Click to Email
The ground state geometry of dimers on the C(100), Si(100) and Ge(100) surfaces have been the subject of much study and controversy, particularly in the case of the silicon surface. There are at least two issues which have not been resolved. First, theoretical calculations for Si(100) have favored both the buckled and unbuckled dimer geometry as the ground state. The most recent cluster calculations favor an unbuckled ground state while the most recent slab calculations favor a buckled ground state. Second, the driving force for dimer buckling is still not well understood. There have been suggestions that slab calculations predict the unbuckled ground state for Si(100) because of the inadequate treatment of electron correlation. We performed density functional cluster calculations for all three surfaces in an attempt to resolve these issues. We find that a number of previous cluster calculations have not dealt satisfactorily with the geometric constraints applied during geometry optimization. Our calculations resolve the differences in ground state geometry, dimer bond length and energetics between cluster and slab calculations. We also find that buckling is driven by a kinetic energy decrease, and that for silicon and germanium this dominates the increase in potential energy with buckling. For carbon the decrease in kinetic energy with buckling is less than the increase in potential energy and, hence, buckling is energetically unfavorable. We can trace this difference in behavior to the small core size of the carbon atom compared to silicon and germanium.