We demonstrate a method for the controlled implantation of single ions into a silicon substrate with energy of sub-20-keV. The method is based on the collection of electron-hole pairs generated in the substrate by the impact of a single ion. We have used the method to implant single 14-keV 31 P ions through nanoscale masks into silicon as a route to the fabrication of devices based on single donors in silicon.

We present measurements of the conduction of nondegenerate free electrons along a low-dimensional channel at low temperatures, using surface-state electrons on liquid helium in novel microelectronic devices. Above 1 K, the electrons form an ideal classical Drude conductor. Below 1 K, Coulomb interactions produce electronic spatial order, leading to strong non-Ohmic effects and negative differential conductivity. Evidence is presented for self-organized current filaments in the channel, created by a nonequilibrium phase transition. Periodic conductance oscillations suggest an anisotropic spatial order with lines of electrons along the channel edges.

We demonstrate time-resolved control and detection of single-electron transfers in a silicon device implanted with exactly two phosphorus donors. Charge state relaxation at millikelvin temperature is shown to be dominated by phonon emission and background charge fluctuations for low energies, while higher-order processes take over at higher energies. Our results reveal relaxation times for single-donor charge states of several milliseconds, which have significant implications for single-atom nanoelectronics.