A field-emission source of charges based on nanotubes for low-temperature experiments

Abstract

Methods for the production of field-emission sources of charges on the basis of carbon nanotubes are described. These sources can be used to study the properties of injected charges in cryogenic liquids and crystals (the area of the source surface is about several square millimeters, the dissipated power is <10−6 W). The first and second batches of sources were produced by means of the deposition of nanotubes from an arc discharge on a flat copper substrate and via mechanical rubbing of nanotubes into a porous metal, respectively. Tests of sources from the first batch in a diode with a gap of 0.5 mm showed that in superfluid He-II, the current of negative charges at a level of 10−12 A arises when the voltage at the cathode is U = −140 V and increases to 10−9 A, when U rises to 170 V. When the voltage polarity changes, the current of positive charges arises in the diode for the voltage U ≥ 240 V. A source from the first batch was used to observe the movement of negative and positive charges in solid-helium samples at T < 75 mK. For second-batch sources, the current of negative charges at a level of 10−12 A in superfluid He-II arises at U = −260 V.