Fabrication of quantum point contacts by engraving   GaAs/AlGaAs-heterostructures with a diamond tip
  We use the all-diamond tip of an atomic force microscope for the direct engraving of high quality quantum point contacts in GaAs/AlGaAs-heterostructures. The processing time is shortened by two orders of magnitude compared to standard silicon tips. Together with a reduction of the line width to below 90 nm the depletion length of insulating lines is reduced by a factor of two with the diamond probes. The such fabricated defect free ballistic constrictions show well resolved conductance plateaus and the 0.7 anomaly in electronic transport measurements. 
J. Regul, U. F. Keyser, M. Paesler, F. Hohls, U. Zeitler, R. J. Haug,   A. Malave, E. Oesterschulze, D. Reuter, and A. D. Wieck