Optical second harmonic generation spectrum of Ag/Si(111) reconstructed surfaces
Abstract
Optical second harmonic generation (SHG) spectra were measured at Ag/Si(111) reconstructed surfaces; the excitation photon energy ranged from 1.0 to 1.7 eV. The Si(111) surface exhibited two peaks resonant to the transition between the surface states of the 7×7 reconstruction at 1.15 and 1.35 eV. These peaks disappeared in the Ag deposition at room temperature with the completion of the Ag-induced 1×1 surface structure. Instead, the E'0 transition peak red-shifted to appear at 1.6 eV. The peaks of the 7×7 reconstruction disappeared at 0.5 monolayers in the deposition at 400 °C, and two new peaks then grew at 1.15 and 1.45 eV with the appearance of the Ag-induced 3×3 reconstruction. The peak at 1.15 eV was reasonably assumed to be the transition from the free-electron-like surface state to the surface Umklapp empty state of the 3×3-Ag reconstruction. The intense peak at 1.45 eV was tentatively assigned to the multipole plasmon excitation at the Si(111) 3×3-Ag reconstructed surface with a metallic nature.
- Publication:
-
Physical Review B
- Pub Date:
- April 2001
- DOI:
- 10.1103/PhysRevB.63.155413
- Bibcode:
- 2001PhRvB..63o5413H
- Keywords:
-
- 78.66.-w;
- 73.20.-r;
- 73.20.At;
- 73.20.Mf;
- Optical properties of specific thin films;
- Electron states at surfaces and interfaces;
- Surface states band structure electron density of states;
- Collective excitations