  Research in semiconductor physics has advanced to the study of
two-dimensional (2D) materials where the surface controls electronic transport.
A scanning probe microscope (SPM) is an ideal tool to image electronic motion
in these devices by using the SPM tip as a scanning gate. In prior work for a
two dimensional electron gas (2DEG) in a GaAs/AlGaAs heterostructure, a number
of phenomena were imaged, including electron flow from a quantum point contact,
and tuning of a few electron quantum dot. This approach was also used to study
InAs quantum dots grown in a InAs/InP nanowire heterostructure. New
two-dimensional materials such as graphene show great promise for fundamental
research and applications. We have extended or prior work to image the motion
of electrons along cyclotron orbits in single atomic layer graphene passing
from one point contact to a second point contact on the first magnetic focusing
peak in graphene. The charged SPM tip defects electrons passing from one
contact to the other, changing the conductance. A plot of the change in
conductance vs. tip position presents an image of electron flow. A low
temperature Scanning Capacitance Microscope (SCM) with a sensitive charge
preamplifier located near the SPM tip achieves a charge noise level 0.13
e/Hz1/2 with high spatial resolution 100 nm, which promises to be useful to
study electronic behavior in nanoscale devices.
