Charge Pumping Through a Single Donor Atom
  Presented in this paper is a proof-of-concept for a new approach to single electron pumping based on a Single Atom Transistor (SAT). By charge pumping electrons through an isolated dopant atom in silicon, precise currents of up to 160 pA at 1 GHz are generated, even if operating at 4.2 K, with no magnetic field applied, and only when one barrier is addressed by sinusoidal voltage cycles. 
G. C. Tettamanzi, R. Wacquez and S. Rogge
cond-mat.mes-hall