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(Color online) (a) Conductance measured as a function of applied gate voltage for four different gate compositions. (b) Leakage current per of gate electrode measured as a function of applied voltage for the same four samples. Gates of sputtered Au demonstrate levels of leakage several orders of magnitude lower, on average, and possess strong coupling to the 2DEG.
(Color online) Fabrication steps. (a) The substrate is spin coated with 495 PMMA. (b) Electron beam lithography is used to define the device pattern. (c) PMMA exposed during the e beam writing process is removed after developing. The sample is then placed in a BOE solution for to remove layer. (d) A thin layer of gold is sputtered onto the surface. To allow for lift-off, the sputtered layer must be kept to a minimum thickness. (e) A thicker layer of gold is evaporated on top of the sputtered gold layer. (f) Lift-off in hot acetone leaves an intact device with excellent leakage properties.
(Color online) Current through a split gate, fabricated with a sputtered layer of gold, as a function of applied voltage. Stepwise depopulation of edge channels as evidenced through decreasing steps in current, as well as a pinch off voltage around , indicate excellent gate characteristics. Inset: SEM picture of the split gate structure.
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