  Transport measurements are powerful tools to probe electronic properties of
solid-state materials. To access properties of local electronic states in
nanostructures, such as local density of states, electronic distribution and so
on, micro-probes utilizing artificial nanostructures have been invented to
perform measurements in addition to those with conventional macroscopic
electronic reservoirs. Here we demonstrate a new kind of micro-probe: a fast
single-lead quantum dot probe, which utilizes a quantum dot coupled only to the
target structure through a tunneling barrier and fast charge readout by RF
reflectometry. The probe can directly access the local electronic states with
wide bandwidth. The probe can also access more electronic states, not just
those around the Fermi level, and the operations are robust against bias
voltages and temperatures.
