Charge Sensitivity Enhancement via Mechanical Oscillation in Suspended Carbon Nanotube Devices

Single
electron transistors (SETs) fabricated from single-walled
carbon nanotubes (SWNTs) can be operated as highly sensitive charge
detectors reaching sensitivity levels comparable to metallic radio
frequency SETs (rf-SETs). Here, we demonstrate how the charge sensitivity
of the device can be improved by using the mechanical oscillations
of a single-walled carbon nanotube quantum dot. To optimize the charge
sensitivity δQ, we drive the mechanical resonator
far into the nonlinear regime and bias it to an operating point where
the mechanical third order nonlinearity is canceled out. This way
we enhance δQ, from 6 μe/(Hz)1/2 for the static case to 0.97 μe/(Hz)1/2 at a probe
frequency of ∼1.3 kHz.