Low Temperature Force Microscopy on a Two-Dimensional Electron Gas

When: Tuesday, October 18, 2011 at 2:00 pm
Where: DA 114
Speaker: Dr. James Hedberg
Organization: McGill University
Sponsor: CIRCS

We have designed and constructed an atomic force microscope (AFM) capable of operation at milliKelvin temperatures and extremely strong magnetic fields (16T). This unique instrument is mounted to the mixing chamber of a standard dilution refrigerator. Using this tool, we have further developed methods to probe charge transport in semiconductor materials, specifically edge states of a 2-dimensional electron gas (2DEG) in the quantum Hall regime. Among other techniques, we apply an AC excitation signal to a two-dimensional electron gas and monitor the electrostatic potential distribution via the oscillation dynamics of a piezoelectric quartz tuning fork with a conductive tip attached to one tine. The instrument will be discussed in detail as well as some recent experiments involving deeply buried 2DEGs.