Selected Applications
attoRAMAN
Electronics
scan controller and software
dedicated FPGA-based RAMAN controller providing coarse positioning and scanning signals for sample
positioning and scanning in x, y, and z direction; control software for extensive RAMAN signal data
acquisition and post processing
Options
sample holder upgrade
ASH/QE/4CX quick-exchange sample holder with 8 electrical contacts and integrated heater with
calibrated temperature sensor
Raman Spectroscopy on Graphene
The figure to the left shows magneto-Raman measurements recorded at 4 K
on an exfoliated single crystal of natural graphite with unprecedented spa-
tial resolution (approx. 0.5 μm), while sweeping the magnetic field from -9 T
to +9 T. The data were recorded on a single graphene flake and demonstrate
the crossing of the E2g phonon energy with the electron-hole separation
between the valence and conduction Landau levels (-N,+M) of the Dirac
cone. Resonant hybridization of the E2g phonon is a specific signature of
graphene flakes which display very rich Raman scattering spectra varying
strongly as function of magnetic field [1].
[1] C. Faugeras et al., Phys. Rev. Lett. 107, 036807 (2011); (attocube application labs, 2011; work in
cooperation with C. Faugeras, P. Kossacki, and M. Potemski, LNCM I - Grenoble, CNRS_UJF_UPS_INSA France)
Magneto-Raman Microscopy for Probing Local Material
Properties of Graphene
The combination of confocal Raman microscopy and magnetic fields at 4 K yields
the opportunity to investigate and tune the electron-phonon interaction in
graphene and few-layer graphene. In particular, excitations between Landau
levels can resonantly couple to the Raman active long wavelength optical
phonon (G-phonon), when their energies are matched, resulting in magne-
to-phonon resonances (MPRs). Such resonances at ±3.7 T are presented in the
figure and highlighted by arrows. The details of the coupling depend on various
material properties of the investigated graphene layer. From the MPRs, device
parameters such as the electron-phonon coupling constant or the Fermi velocity
of the charge carriers can be extracted. Interestingly for low charge carrier dop-
ing, the Fermi velocity shows signatures of many-body interaction effects [2].
[2] Nat Comms, Nature Publishing Group, 2015, 6, 8429
attoMICROSCOPY
Sophisticated Tools for Science
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