  The ongoing development of single electron, nano and atomic scale
semiconductor devices would benefit greatly from a characterization tool
capable of detecting single electron charging events with high spatial
resolution, at low temperature. In this work, we introduce a novel Atomic Force
Microscope (AFM) instrument capable of measuring critical device dimensions,
surface roughness, electrical surface potential, and ultimately the energy
levels of quantum dots and single electron transistors in ultra miniaturized
semiconductor devices. Characterization of nanofabricated devices with this
type of instrument presents a challenge: finding the device. We therefore also
present a process to efficiently find a nanometre size quantum dot buried in a
$10 \times 10~\text{mm}^2$ silicon sample using a combination of optical
positioning, capacitive sensors and AFM topography in vacuum.
