Primary Tunnel Junction Thermometry

Abstract

We describe the concept and experimental demonstration of primary thermometry based on a four probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future.

Accurate Coulomb blockade thermometry up to 60 kelvin

“…Finally, we discuss the comparison of the CBT sensor with a single junction device (SJT, [7,15,21]). The obvious advantage of the SJT over a multi junction device is that no scatter of junction resistance in the array influences the result.…”

“…7, left inset: one central junction is connected via four long arrays of tunnel junctions allowing a four probe measurement of the central junction and creating a suitable electromagnetic environment for precise thermometry [15]. We use FIG.…”

“…The lift-off is done by immersing the wafer in acetone at ambient temperature. Figure 1 depicts a small section of one sensor that consists in total of an array of 77 junctions in series to increase the signal strength and to suppress the influence of the electromagnetic environment [8,15] and in 30 parallel rows to reduce the final resistance of the sensor to a value of about 100 kΩ in order to facilitate the electrical measurement. Already the design of the mask takes the main requirement of the sensor, the small junction size We observe a remarkable reproducibility over the full 77x30 junction array, note that the 2nd shadow, that falls in the image always on the left, has a slightly reduced size due to partial blocking of mask from the first angle evaporation.…”

Comparison of Coulomb Blockade Thermometers with the International Temperature Scale PLTS-2000

“…In the sensors reported in this work, we expect the fabrication inhomogeneity of the junction resistances to be below 10% resulting in an uncertainty in temperature lower than 2% [10]. In addition to the conventional CBT thermometer, we present in this work a first comparison of a single junction thermometer (SJT) [7], that is not affected by fabrication inhomogeneity, with the PLTS-2000 scale. SJT demands on the other hand an enhanced experimental effort to precisely measure the smaller signal experimentally at low temperatures.…”

“…Along with an increased understanding of such structures, improved production technologies made new classes of thermometers available [5]. As an example, thermometers based on a tunnel junction or arrays of them as the Coulomb blockade thermometer (CBT) [6], the single junction thermometer (SJT) [7] or the shot noise thermometer (SNT) [8,9] have been shown to work in a broad temperature range. The mentioned thermometers can be operated in primary mode because the measured quantity is in these devices directly linked to temperature without any need of a calibration against a temperature scale or reference.…”