mK-ready Modules
Scanning Gate Microscopy (SGM)
SGM utilizes the ability of an AFM tip to influence the
electrostatic properties of a sample locally. By applying
voltage to the scanning tip, the tip acts as a movable
electrical gate that can modify electrostatic potential
for electrons in the sample and thus enables exploring
electronic and transport properties at the nanoscale
(Figure 1).
AMP
ASC500
Lock-In
S-xyz
This approach has already been proven useful at
temperatures > 4K in e.g. imaging current flow through
quantum point contacts [M.P. Jura et al., Nature Phys.
3, 841 (2007)], or in visualizing coherent transport
and universal conductance fluctuations in graphene
[J. Berezovsky et al., Nanotechnology 21, 274013
(2010)]. By adopting SGM to mK temperatures, quantum
phenonema can be probed since electron mobilities
further increase along with thermal fluctuations further
decreasing, which is the prerequisite for reaching the
necessary energy resolution.
Tuning-fork-based AFMs with wire-type tips are better
suited for SGM than cantilever-based AFMs, since the
cantilever strongly influences the capacitive coupling
between tip and sample, and hence washes out the
localization of the tip potential. The attoAFM III
is the perfect microscope platform for electrical
transport measurements on the nanoscale.
Figure 2: A typical potential landscape for a scanning
gate experiment on a GaAs/AlGaAs heterostructure. It
demonstrates the size of the tip-induced potential as
well as the influence of the disorder potential (image
courtesy of R. Steinacher, ETH Zurich, Switzerland).
Z-feedback
DAQ
P-xyz
attoAFM III
Figure 1
AFM tip
top gates
Fermi level
electrostatic potential in 2DEG
Figure 2