  We have developed nano-scale double-gated field-effect-transistors for the
study of electron states and transport properties of single
deliberately-implanted phosphorus donors. The devices provide a high-level of
control of key parameters required for potential applications in
nanoelectronics. For the donors, we resolve transitions corresponding to two
charge states successively occupied by spin down and spin up electrons. The
charging energies and the Lande g-factors are consistent with expectations for
donors in gated nanostructures.
