Effects of electrostatic confinement in a silicon single-electron pump

Nanoscale single-electron pumps could serve as the realization of a new quantum standard of electrical current. Here, a silicon quantum dot with tunable tunnel barriers is used as a source of quantized current. By controlling the electrostatic confinement of the dot via purposely engineered gate electrodes, we show that the robustness of the pumping mechanism can be dramatically enhanced and the detrimental effects due to non-adiabatic transitions are largely reduced. Our pump can produce a current in excess of 80 pA with experimentally determined relative uncertainty lower than 50 parts per million.