Tunneling images of a 2D electron system in a quantizing magnetic field
  We have applied a scanning probe method, Subsurface Charge Accumulation (SCA) imaging, to resolve the local structure of the interior of a semiconductor two-dimensional electron system (2DES) in a tunneling geometry. Near magnetic fields corresponding to integer Landau level filling, submicron scale spatial structure in the out-of-phase component of the tunneling signal becomes visible. In the images presented here, the structure repeats itself when the filling factor is changed from nu=6 to nu=7. Therefore, we believe the images reflect small modulations in the 2DES density caused by the disorder in the sample. 
I. J. Maasilta, Subhasish Chakraborty, I. Kuljanishvili, S. H.   Tessmer, M. R. Melloch