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attoCFM & attoRAMAN Fields of Applications
low temperature confocal microscopy low temperature confocal microscopy
2D materials: Dichalcogenides & Graphene Quantum dot photoluminescence
This class of 2D materials offers a rich variety of physics useful for fields
such as optoelectronics. It has been in the center of quantum optics
research over 10 years now since the advent of graphene. Typically these
materials are characterized and further studied at low temperatures, to
minimizes thermal broadening of the photoluminescence spectra, and often
under high magnetic fields in Faraday & Voigt geometry. The attoCFM I offers
an ideal platfrom for magneto-optical studies in conjunction with the
automated attoDRY2100 cryostat.
One prominent yet difficult example of spectroscopy of semiconductor
quantum dots (QDs) is the resonant optical laser excitation of single photon
emitters. This yields additional information about the emitters than the
more ubiquitous non-resonant excitation. The attoCFM I can be upgraded
with a resonant fluorescence package, that permits alignment free switching
between off resonant PL measurements and RF thanks to our cryogenic apochromatic
objectives. The integrated high precision rotators enable extinction ratios of
107 [1], just a factor 10 away from the world record in research labs [2], while
allowing an unprecedented flexibility of use.
[1] attocube AppNote M45 - attoCFM I - Resonant spectroscopy on a single quantum dot
[2] A.V. Kuhlmann et al., Review of Scientific Instruments 84, 073905 (2013).
µ-Raman spectroscopy Photocurrent measurements
Graphene has seen tremendous interest in solid state physics and Raman
spectroscopy was one of the central techniques to characterize its properties
from the start. The attoRAMAN offers the unique possibility to extend such
studies not only over a broad temperature range between 1.65 .. 300 K, but
also to high magnetic fields. In cooperation with the group of M. Potemski,
we recorded magneto-Raman spectra at 4 K on an exfoliated single crystal of
natural graphite with unprecedented spatial resolution (approx. 0.5 μm), while
sweeping the magnetic field from -9 T to +9 T, showing 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. Using our sample holders with electrical contacts, photocurrent
measurements in variable field and temperature are easily possible.
For example, the group of P. Sutter has used our fiber-based attoCFM II for
spatially resolved photocurrent measurements on a graphene field-effect
device in the QHE regime. They studied the distribution of Landau levels
and its relation with macroscopic transport characteristics [1].
The exceptional stability and the ease of use of the attoCFM microscope
greatly facilitated these measurements and allowed for measuring working
devices in magnetic fields from -9 to +9 T.
[1] G. Nazin, Y. Zhang, L. Zhang, E. Sutter, P. Sutter, Nature Physics 6, 870–874 (2010)
(attocube application labs, 2011; work in cooperation with C. Faugeras, P. Kossacki, and M.
Potemski, LNCM I - Grenoble, CNRS_UJF_UPS_INSA France)