The consortium brings together seven leading European other National Metrology Institutes (NMIs), two NMIs from outside Europe NIMT from Thailand and KRISS from Korea and is further strengthened by research groups from a university and two CNRS research institutes. Together these 11 partners form an outstanding consortium with the excellence necessary to meet the challenging objectives of the project. The most critical and challenging issue of the project will be the quality and durability of the graphene sheets and devices. To maximise the probability of success, this issue will be tackled by more than one partner, each starting with their own approach, but with mutual exchange of methods and experience.
PTB will coordinate the project and lead WP3 and WP5. PTB has long standing experience and expertise in the development and use of QHE standards, both with traditional GaAs-based devices and with graphene. The use of the QHE at AC frequencies was first suggested at PTB and, together with METAS, a successful feasibility study was conducted within the EMRP JRP SIB51 GraphOhm. In this project, PTB will contribute to the fabrication and characterisation of graphene devices for AC applications in WP1 and to the development of the QHE application at AC with conventional and digital Josephson bridges in WP2 and WP3.
CMI has facilities and expertise in the development of digital bridges for impedance measurements, in the DC and AC characterisation of the QHR, and in the design and realisation of precision auxiliary electronic circuits. In this project, CMI will mainly contribute to the development of a digital quantum impedance standard based on the AC QHE in graphene, to the characterisation of scaling devices and to the characterisation of DC and AC QHR under specific conditions.
INRIM is the Italian National Metrology Institute, with a long tradition in impedance metrology. In recent years its research has been focussed on the realisation of digital bridges and has implemented a realisation of the capacitance standards with a traceability chain involving digitally-assisted bridges. In the last five years INRIM researchers have prepared or contributed to more than 10 international review papers, and a book in the field of impedance metrology. INRIM was leader of WP 2 “Digital bridges” of EMRP JRP SIB53 AIMQuTE, and the leader of WP 1, "Impedance measurement infrastructure" of EMPIR JRP 17RPT04 VersICal. INRIM actively participates in several EMPIR projects, often as coordinator or WP leader and will lead and WP4 in this project.
LNE has been involved in the development of the quantum Hall resistance standard in different types of graphene devices since 2007. Recently they have demonstrated 10-9-accurate operation in relaxed experimental conditions for a quantum resistance standard based on graphene grown by CVD on SiC by CNRS. LNE also has a broad range of experience in the AC traceability of capacitance and resistance at audio frequencies and has developed a new Thompson-Lampard Calculable Capacitor.
METAS has strong expertise in QHE both at DC and AC and in impedance measurements. This expertise will be used to develop a quantum impedance standard using a graphene-based QHR reference and a full Josephson based digital bridge with a bandwidth of up to 100 kHz. METAS will also be involved especially in testing the AC properties of QHE in devices. METAS will lead WP2.
RISE has significant experience in traditional low frequency impedance measurements and DC-QHE measurements using GaAs and graphene devices. RISE also has experience in the development of programmable JVS-based impedance bridges (Josephson bridges) and some experience in the fabrication of graphene QHE devices. RISE has invested in a new cryocooler with a 12 T magnet, which will be used in this project.
VTT has extensive experience in the design and characterisation of quantum Hall devices based on epitaxial graphene, in the development of an accurate dual channel audio frequency sine wave voltage source for impedance metrology and other applications, and in metrological experiments in cryogen free environments. VTT’s main activities will be the development of a cryocooler system hosting both Josephson and QHR devices, and VTT’s earlier experience will be very relevant for these activities.
CNRS will participate in the project through two laboratories: CRHEA will bring its exclusive experience on graphene growth by CVD on SiC, and C2N will support sample processing in a 2500 m2 clean room. The CVD-graphene-on-SiC devices, on which LNE reported 10-9-accurate QHR in relaxed operating conditions, were fabricated by CNRS. CNRS will mainly be involved in Tasks 1.1 and 1.2, focusing especially on fabricating devices based on CVD-grown graphene on SiC. CNRS will lead WP1.
NIMT has experience in traditional low frequency impedance measurements and conventional DC QHE measurements using GaAs devices. NIMT has a cryocooler with a 17 T magnet and also operates a Josephson voltage system. NIMT is planning to set up a new laboratory with the required measurement standards and measurement systems including the capacity building of staff through training and participating in research. NIMT will participate in developing the Josephson impedance bridges at PTB. NIMT will further specify the requirements for knowledge transfer of the resulting system from experienced NMIs to less experienced ones.
POLITO has broad experience in DC and AC analytical and numerical circuit analysis and in the modelling of QHE devices and circuits. POLITO also has broad experience in the design and characterisation of digital bridges. POLITO’s main activities will include the automation and validation of a four terminal-pair, fully-digital bridge for the comparison of resistance and capacitance standards and for the modelling of AC-QHR. As a university partner running a PhD programme in Metrology, POLITO will also contribute to knowledge transfer.
KRISS has facilities and expertise for the growth of epitaxial graphene, for device fabrication, and for the DC metrological characterisation of the device. KRISS also has experience on impedance measurements with analogue and digital bridges. KRISS’s main contributions include the fabrication and characterisation (WP1) of graphene quantum Hall devices, digital bridge measurements and the developments for the realisation of the farad from the graphene QHE for frequencies up to 100 kHz and capacitance up to 10 nF, and the integration of a graphene AC-QHE device and a digital bridge.