Bertrand KIERREN (Institut Jean Lamour, Nancy)
Abstract:
Reducing the size of solids down to the nanometer scale leads to new physical properties due to the quantum confinement of carriers.
Since a couple of decades quantum systems are intensively investigated for their fundamental properties or for applications, especially in semi conductors.
From Angle Resolved Photo Emission Spectroscopy (ARPES) and/or Scanning Tunnelling Spectroscopy (STS,) several papers report on spectral properties of quantum well states (QWS’s) that develop in ultra thin metallic films epitaxially grown on semiconducting or metallic single crystals like Ag/Si(111), Pb/Si(111), Ag/Fe(001)... In this speach i will present results on QWS’s obtained in thin Pb films grown on Ag(111). From low temperature STM and STS investigations i will show how the QWS’s depend not only of the thickness of the films but also of the phase shift of the electron wave function occuring at the reflection at both boundaries of the film. Thank’s to the high spatial resolution of STS (down to atomic scale) i will show how it is possible to modfify the QWS’s by growing a monolayer of PbO on top of the Pb film. An atomic scale study of the phase shift at the PbO/Pb interface will be presented and discussed.