Study of Electron Electron Interaction by Scanning Probe Microscopy

Matthew Prior

SPM insides
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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