  Several solid state quantum computer schemes are based on the manipulation of
electron and nuclear spins of single donor atoms in a solid matrix. The
fabrication of qubit arrays requires the placement of individual atoms with
nanometer precision and high efficieny. In this article we describe first
results from low dose, low energy implantations and our development of a low
energy (<10keV), single ion implantation scheme for 31P(q+) ions. When 31P(q+)
ions impinge on a wafer surface, their potential energy (9.3 keV for P15+) is
released, and about 20 secondary electrons are emitted. The emission of
multiple secondary electrons allows detection of each ion impact with 100%
efficiency. The beam spot on target is controlled by beam focusing and
collimation. Exactly one ion is implanted into a selected area avoiding a
Poissonian distribution of implanted ions.
