Image of the Month

July 2013

Imaging the Electron-Phonon Interaction at the Atomic Scale


12nm x 12nm STM and IETS maps simultaneously acquired on the surface of the 9 ML Pb island at a 1 nA tunneling current.The STM image (a) was obtained at a tunnel bias of 750 mV. The IETS image (b) was acquired at a tunnel bias of 9 mV.(c) Cross section of the IETS image in (b)

The inelastic electron tunneling spectrum measured on top of the 9 ML Pb island. Resonant phonon emission peaks develop at a 9 mV tunnel bias. Inset: tunnel I-V curve for the same island measured in a broader bias range.Steps on this curve are due to QW resonances from transverse electron interference. The decrease of the barrier height at large bias was compensated by a slow increase of a tunneling gap, at a rate of 0.4 Å per |V|.

PhysRevLett.109.166402 DOI 10.1103/Physlet.109.166402

Igor Altfeder, K. A. Matveev, A. A. Voevodin

RHK Technology VT UHV STM Model UHV300

Control System:
RHK Technology SPM 1000

Thin Pb films epitaxially grown on 7 7 reconstructed Si(111) represent an ideal model system for studying the electron-phonon interaction at the metal-insulator interface. For this system, using a combination of scanning tunneling microscopy and inelastic electron tunneling spectroscopy, we performed direct real-space imaging of the electron-phonon coupling parameter. We found that ! increases when the electron scattering at the Pb=Sið111Þ interface is diffuse and decreases when the electron scattering is specular. We show that the effect is driven by transverse redistribution of the electron density inside a quantum well.