Imaging Inter-Edge State Scattering Centers in the Quantum Hall Regime
  We use an atomic force microscope tip as a local gate to study the scattering between edge channels in a 2D electron gas in the quantum Hall regime. The scattering is dominated by individual, microscopic scattering centers, which we directly image here for the first time. The tip voltage dependence of the scattering indicates that tunneling occurs through weak links and localized states. 
Michael T. Woodside, Chris Vale, Paul L. McEuen, C. Kadow, K. D.   Maranowski, A. C. Gossard