STM light emission from Si(1 1 1)3×3-Ag surface

Light emission stimulated by scanning tunneling microscope (STM-LE) from a Si(1 1 1)3×3-Ag surface was studied by a light detection system combined with a UHV-STM. A single broad peak appears in the emission (fluorescence) spectra and the peak energy linearly shifts to higher energies with increasing bias voltage. Photon maps clearly reveal the steps between the hole–island pairs in the Si(1 1 1)3×3-Ag surface, and those steps show dark contrast for the positive bias voltage and bright contrast for the negative bias voltage, respectively. The Si(1 1 1) 7×7 and Si(1 1 1)3×3-Ag regions show a clear contrast in the photon map, which indicates that the STM-LE is sensitive to the surface structure. The STM-LE from Si(1 1 1)3×3-Ag is well understood from the inverse photoemission process or inelastic tunneling process. The observed emission peak can be attributed to the transition of electrons near the Fermi level in the tungsten tip to the surface state of Si(1 1 1)3×3-Ag reported by the inverse photoemission measurement.