Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 64: Scanning Probe Techniques: Method development

O 64.8: Poster

Dienstag, 21. März 2017, 18:30–20:30, P2-OG3

Tuning the functionality of a junction field effect transistor at cryogenic temperatures: new prospects and possible applications — •Meike Flebbe, Paul Graf, Christian A. Bobisch, Hermann Nienhaus, and Rolf Möller — Faculty of Physics, Center for Nanointegration Duisburg-Essen, University of Duisburg-Essen, 47048 Duisburg, Germany

By cooling a conventional junction field-effect transistor (JFET) to 80 K an electrometer with extremely high impedance can be realized. It may be used as a detector for ultimately low currents or charges, e.g. for low temperature scanning probe microscopy (SPM). The characteristics of the JFET at room temperature and in the cooled state were recorded and compared. While the gate leakage current at about 300 K is in order of magnitude of a few pA, it becomes very low when the JFET is cooled to 80 K. A careful measurement provides an estimate of the leakage current of 4 × 10−20 A [1]. The electrometer can be used from DC up to a frequency of 10 kHz. Without reduction of the bandwidth signal of a few µV can be detected. Working at low frequencies currents as low as a few attoampere can be detected. Despite the high sensitivity the sensor is fairly robust. If the input voltage is out of the operational range the forward current or the Zener current of the gate junction protects the transistor against destructive charging. Finally, different schemes have been developed to apply the sensor for scanning tunneling microscopy and potentiometry.

[1] R. Möller and H. Nienhaus, patent pending, Open FET Sensor, Provendis Ref.-Nr: 4817

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