Thursday, August 1, 2013

1307.8163 (D. Kölbl et al.)

Transport spectroscopy of disordered graphene quantum dots etched into a
single graphene flake

D. Kölbl, D. M. Zumbühl
We present transport measurements on quantum dots of sizes 45, 60 and 80 nm etched with an Ar/O2-plasma into a single graphene sheet, allowing a size comparison avoiding effects from different graphene flakes. The transport gaps and addition energies increase with decreasing dot size, as expected, and display a strong correlation, suggesting the same physical origin for both, i.e. disorder-induced localization in presence of a small confinement gap. Gate capacitance measurements indicate that the dot charges are located in the narrow device region as intended. A dominant role of disorder is further substantiated by the gate dependence and the magnetic field behavior, allowing only approximate identification of the electron-hole crossover and spin filling sequences. Finally, we extract a g-factor consistent with g=2 within the error bars.
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