Quantum Transport

Quantum transport involves the study of electronic transport through various nanostructures such as carbon nanotubes, inorganic nanowires and graphene. The first step in this procedure is the fabrication of devices utilizing various lithographic techniques. Electrode arrays are employed for four-probe measurements, allowing us to discriminate between the intrinsic wire resistance and the contact resistance. Highly doped Si wafers with a thermally grown SiO2 layer of 100 nm thickness serve as conducting substrates for gate dependent measurements. The gate measurements are carried out in back-gated or electrochemically gated configurations. In addition to DC probe measurements, AC measurements are also in routine use where the impedance is analyzed in a frequency range of up to 2 MHz. Furthermore, electrical measurements are performed in a helium cryostat between 1.3 K and 300 K under magnetic fields of up to 14 T. In addition, a UHV chamber is available offering the possibility to prepare clean nanostructures or film surfaces, and explore their charge transport behavior as a function of surface modification. Furthermore, we are studying the local photocurrent response of different nanostructures, to which end we are currently expanding the measurement capability down to low temperatures (< 1 K) and applied magnetic fields (up to 15 Tesla).

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