STM light emission from Si(111)root 3 x root 3-Ag surface

Light emission stimulated by scanning tunneling microscope (STM-LE) from a Si(111)root3 x root3-Ag surface was studied by a light detection system com bined with a UHV-STM. A single broad peak appears in the emission (fluoresc ence) spectra and the peak energy linearly shifts to higher energies with i ncreasing bias voltage. Photon maps clearly reveal the steps between the ho le-island pairs in the Si(111)root3 x root3-Ag surface, and those steps sho w dark contrast for the positive bias voltage and bright contrast for the n egative bias voltage, respectively. The Si(111) 7 x 7 and Si(111)root3 x ro ot3-Ag regions show a clear contrast in the photon map, which indicates tha t the STM-LE is sensitive to the surface structure. The STM-LE from Si(111) root3 x root3-Ag is well understood from the inverse photoemission process or inelastic tunneling process. The observed emission peak can be attribute d to the transition of electrons near the Fermi level in the tungsten tip t o the surface state of Si(111)root3 x root3-Ag reported by the inverse phot oemission measurement. (C) 2001 Elsevier Science B.V. All rights reserved.