Paper NS+2D+AS-WeA11
Determining the Jahn-Teller Stabilization Energy of Surface Vacancies on Si(111)-√3 x √3:B
Wednesday, October 23, 2019, 5:40 pm, Room A222
The vacancy defect on the Si surface becomes increasingly important with the device scaling because it works as the charge trapping and scattering center with varying ionization states. Yet its characteristics have not been addressed as comprehensively as the bulk vacancy in Si. In fact, its behavior would be affected by the gap state evolution and the Fermi level pinning on the Si surface. On the other hand, the (111)-surfaces of Si come to have the √3 x √3 reconstruction instead of the 7 x 7 one when they are heavily B-doped [1,2]. This √3 x √3 surface does not evolve any energy state within the band gap, being contrary to the 7 x 7 one [2]. Also, the Fermi level is shifted to the valence band maximum on the √3 x √3 surface whereas it is pinned in the middle of the gap on the 7 x 7 surface [2]. Hence the vacancy defects on the two surfaces may have dissimilar characteristics from each other. Here, we generate the vacancy defects on the √3 x √3 surface via the atom manipulation technique and measure their structural and electronic properties by using the scanning tunneling microscopy and spectroscopy. We find that, unlike the 7 x 7 surface, the vacancy defects on the √3 x √3 surface are Jahn-Teller distorted in the ground state, but undergo the symmetry-restoring transition when gated by the external bias. We also determine the energy gain or stabilization energy of the Jahn-Teller transition quantitatively. These findings would extend our knowledge on the surface vacancies on Si and eventually contribute to the fabrication of better-performing nanometer-scale devices.[1] I.-W. Lyo, E. Kaxiras, and Ph. Avouris, Phys. Rev. Lett. 63, 1261 (1989).
[2] D. Eom, C.-Y. Moon, and J.-Y. Koo, Nano Lett. 15, 398 (2015).