Study of Electron Electron Interaction by Scanning Probe Microscopy
Matthew Prior
I have created a low temperature Scanning Probe Microscope (SPM). This
is a purely electronic SPM based on the "Besoke beetle" design. It is designed
to operate in our He3 and dilution refrigerators. I have fabricated a low
temperature amplifier based on a High Mobility Electron Transistor (HMET)
for low temperature amplification and learned the sample preparation techniques
necessary for the creation of microstructures. I intend to apply this to
the study of both lateral and mobile vertical quantum dots. In the lateral
quantum dots I will scan a depletion region created by the tip across the
dot. I can then measure the change in the Coulomb blockade peaks as a function
of the tip position (Scanning Gating Microscopy). This will give information
about the probability densities of their highest energy electrons. In a
different experiment, a vertical mobile quantum dot will be induced under
the scanning tip by accumulating electrons in an empty quantum well. The
Coulomb blockade pattern of this dot can then be then observed by Scanning
Capacitance Microscopy (SCM). This dot can then be moved laterally through
the well by the tip. When this dot interacts with impurities in the quantum
well changes will result in the Coulomb blockade pattern. In both the
cases of lateral and vertical quantum dots, we will be able to test the limits
of the validity of the constant interaction model.
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