New Publication: Novel circuit design for high-impedance and non-local electrical measurements of two-dimensional materials

Anja Roeding Latest publications
Fig 1: High-impedance measuring chamber and circuitry. (a) Schematic drawing of the vacuum chamber used to perform the measurements, configured to retrofit a magnet or cryostat. In order to avoid stray capacitance, each SMA connector is wired to the device under test (DUT) using a single-core insulated copper wire. (b) Schematic of the break-out box used to interface the DUT to the measuring instruments. For each BNC connector, it is possible to choose two separate terminals for the shielding (GND1 and GND2), in order to ensure complete floating of the measuring probes. (c) Model of the printed circuit board (PCB) used to mount the DUT. The pins are spaced 5 mm apart to ensure high insulation. (d) Photograph of the actual chamber mounted on an Oxford Instruments Microstat MO superconducting magnet.

Jake Mehew‘s work on an optical isolator circuit which grants access to high-impedance states by electrically decoupling the current-injection from the voltage-sensing circuitry has recently been published in AIP Review of Scientific Instruments: “Two-dimensional materials offer a novel platform for the development of future quantum technologies. However, the electrical characterisation of topological insulating states, non-local resistance, and bandgap tuning in atomically thin materials can be strongly affected by spurious signals arising from the measuring electronics. Common-mode voltages, dielectric leakage in the coaxial cables, and the limited input impedance of alternate-current amplifiers can mask the true nature of such high-impedance states. Here, we present an optical isolator circuit which grants access to such states by electrically decoupling the current-injection from the voltage-sensing circuitry. We benchmark our apparatus against two state-of-the-art measurements: the non-local resistance of a graphene Hall bar and the transfer characteristic of a WS2 field-effect transistor. Our system allows the quick characterisation of novel insulating states in two-dimensional materials with potential applications in future quantum technologies.” See the full article in Review of Scientific Instruments, Volume 89, Issue 2, DOI 10.1063/1.5020044

 

 

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