  We report integrated charge sensing measurements on a Si/SiGe double quantum
dot. The quantum dot is shown to be tunable from a single, large dot to a
well-isolated double dot. Charge sensing measurements enable the extraction of
the tunnel coupling, t, between the quantum dots as a function of the voltage
on the top gates defining the device. Control of the voltage on a single such
gate tunes the barrier separating the two dots. The measured tunnel coupling is
an exponential function of the gate voltage. The ability to control t is an
important step towards controlling spin qubits in silicon quantum dots.
