Tunneling electron induced luminescence from indium films on Si(111)

We investigated the growth, electronic states, and tunneling electron induced luminescence of In ultrathin films on Si(111) using scanning tunneling microscopy (STM). The In films (4--8 monolayers) grew layer by layer by deposition at ~100 K. The dI/dVₛ spectra exhibited the quantum-well states confined in the films. We observed luminescence originating from the junction plasmon excited via electron tunneling into the quantum-well state. Thus, by adjusting the thickness of the film at a single-layer level, we were able to modify the photon emission from the STM junction.