Scanning gate microscopy

Scanning gate microscopy (SGM) is a scanning probe microscopy technique with an electrically conductive tip used as a movable gate that couples capacitively to the sample and probes electrical transport on the nanometer scale. Typical samples are mesoscopic devices, often based on semiconductor heterostructures, such as quantum point contacts or quantum dots. Carbon nanotubes too have been investigated.

In SGM one measures the sample's electrical conductance as a function of tip position and tip potential. This is in contrast to other microscopy techniques where the tip is used as a sensor, e.g., for forces.

SGMs were developed in the late 1990s from atomic force microscopes. Most importantly, these had to be adapted for use at low temperatures, often 4 kelvins or less, as the samples under study do not work at higher temperatures. Today an estimated number of ten research groups worldwide use the technique.

References

• 1D probability density observed using scanned gate microscopy: R.Crook, et al., J. Phys.: Condens. Matt., 12, L735 – L740 (2000)
• Coherent Branched Flow in a Two-Dimensional Electron Gas: A. Topinka et al., Nature 410, 183 (2001)
• Scanned Probe Imaging of Single-Electron Charge States in Nanotube Quantum Dots: M. T. Woodside and P. L. McEuen, Science 296, 1098 (2002)
• Imaging fractal conductance fluctuations and scarred wave functions in a quantum billiard: R. Crook et al., Phys. Rev. Lett. 91, 246803 (2003)
• Spatially Resolved Manipulation of Single Electrons in Quantum Dots Using a Scanned Probe: A. Pioda et al., Phys. Rev. Lett. 93, 216801 (2004)
• Imaging and controlling electron transport inside a quantum ring: B. Hackens et al., Nature Phys. 2, 826 (2006)
• Classical Hall effect in scanning gate experiments: A. Baumgartner et al., Phys. Rev. B 74, 165426 (2006), doi:10.1103/PhysRevB.74.165426
• Quantum Hall effect transition in scanning gate experiments: A. Baumgartner et al., Phys. Rev. B 76, 085316 (2007), doi:10.1103/PhysRevB.76.085316
• Imaging Coulomb Islands in a Quantum Hall Interferometer: B. Hackens et al., Nat. Commun. 1, 39 (2010), doi:10.1038/ncomms1038
• Transport inefficiency in branched-out mesoscopic networks: An analog of the Braess paradox: M.G. Pala et al., Phys. Rev. Lett. 108, 076802 (2012)
• Wigner and Kondo physics in quantum point contacts revealed by scanning gate microscopy: B. Brun et al., Nat. Commun. 5, 4290 (2014), doi:10.1038/ncomms5290