Atomic scale investigation of low-energy excitation at surface and interface by inelastic electron tunneling spectroscopy
DIPC Seminars
- Speaker
-
Emi Minamitani (University of Tokyo, Japan)
- When
-
2018/03/05
13:00 - Place
- Donostia International Physics Center
- Add to calendar
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Inelastic electron tunneling spectroscopy (IETS) combined with scanning
tunneling microscopy (STM) allows us to acquire vibrational signals at
surfaces. In STM-IETS, a tunneling electron from the STM tip excites
vibrations whenever the energy of tunneling electron exceeds the vibrational
energies. This opens up an inelastic channel in parallel with the elastic one
and gives rise to an increase/decrease of the conductivity in the STM
junction. As a consequence, a pair of peak and dip shows up at the bias
voltages with respect to the Fermi level corresponding to the energy of
vibrational energy. Until recently, the application of STM-IETS was limited to
the localized vibration of single atoms and molecules adsorbed on surfaces. In
principle, STM-IETS should be capable of detecting the collective lattice
dynamics, i.e., phonons. In this talk, I will introduce the example STM-IETS
measurement for surface and interface phonons and provides the theoretical
analysis behind them. The surface phonon on Cu(110) and interface phonons
relevant of graphene on SiC substrate are good examples. In the former part, I
will provide theoretical formalism about the electron-phonon coupling upon the
electron tunneling based on a simple model Hamiltonian. In the latter case, we
discuss the spatial dependence of the IETS spectrum induced by the excitation
of the interface phonons based on the ab initio calculations.