  We report on millikelvin charge sensing measurements of a silicon double-dot
system fabricated by phosphorus ion implantation. An aluminum single-electron
transistor (SET) is capacitively coupled to each of the implanted dots enabling
the charging behavior of the double-dot system to be studied independently of
current transport. Using an electrostatic gate, the interdot coupling can be
tuned from weak to strong coupling. In the weak interdot coupling regime, the
system exhibits well-defined double-dot charging behavior. By contrast, in the
strong interdot coupling regime, the system behaves as a single-dot.
