10-04 :: April 2010

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Primary Quantum Hall Effect Resistance Standards

W

ith its new molecular beam epitaxy facility, German Physikalisch-Technische Bundes-

anstalt (PTB) continues to be the only metrology institute to produce primary quantum Hall effect resistance standards. So that this would still be the case after the purchase of a more modern molecu- lar beam epitaxy (MBE) facility, the scientists had to come up with some tricks. The new facility is to primarily serve for single-electron tunnelling research – and thus, for instance, for the question of whether also the unit of current ampere can be traced back to natural constants. At first it seemed less suited to the quantum ohm. But by means of the specific alterati-

on of the growth parameters and the layer structure of the crystals, PTB scientists succeeded in the feat of making the facility equally fit for both tasks. Thus, PTB was able to safeguard its competence to also in future be able to produce its own quantum resistance standards. The new MBE facility is, thus, regarded as validated and the supply of PTB with quantum Hall standards has been put on a wider basis. The results will be presented at the forthcoming International Conference for Electro-Magnetic Precision Measure- ments (CPEM) which will take place from June 13 to 18, 2010, in Daejeon/ Korea.

Contact: Klaus Pierz, PTB Working Group 2.53 Low dimensional Electron Systems, Phone: +49531 592-2412: http://www.ptb.de

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This figure shows a sample for quantum Hall effect measurements prepared at PTB. In the middle, the GaAs sample with two Hall bar structures can be seen which are electrically connected with the chip carrier via gold-plated contact areas and very thin wires. © PTB