Dual-Port Reflectometry Technique: Charge identification in nanoscaled single-electron transistors.

Radio-frequency reflectometry (RFR) is a technique that was developed to characterize the properties of transmission lines by observing reflected waveforms. Today, it is widely used in a variety of applications, ranging from the detection of faulty wires in cables and objects buried in the ground to soil moisture detectors and the measurement of dielectric properties of blood. Recently, one important application of this technique, which requires a very small amount of applied power, was developed for the characterization of electronic nanostructures. In this implementation, a microwave radio-frequency (RF) signal is sent to a resonator coupled to the specimen to be studied. If in a specimen the change of some external parameter (e.g., gate voltage) leads to a change of an active [Figure 1(a)] or a reactive (typically, capacitive) load to the resonator, the self-resonance is affected, resulting in a change of magnitude [Figure 2(a)] and phase of the reflected signal. If an impedance matching condition is achieved, the modification of the specimen parameter (e.g., the increase of its resistance) will lead to a very significant change in the reflection coefficient. Here, we discuss two important applications of the RFR technique on nanoscale devices.