  We investigate the effect of electrostatic screening on a nanoscale silicon
MOSFET electrometer. We find that screening by the lightly doped p-type
substrate, on which the MOSFET is fabricated, significantly affects the
sensitivity of the device. We are able to tune the rate and magnitude of the
screening effect by varying the temperature and the voltages applied to the
device, respectively. We show that despite this screening effect, the
electrometer is still very sensitive to its electrostatic environment, even at
room temperature.
