BLANC - Blanc

Biological Growth Medium Integrity Diagnoses using bi-modality tomographies – MICROMAG

Submission summary

The discovery of new classes of materials such as high temperature superconductors, integration of magnetically stored information on ever smaller scales, and new fabrication possibilities for nanometre-scale objects, have faced the experimentalist with an enormous challenge: How can the magnetic behaviour of such materials and objects be characterized, tailored, and manipulated? Remarkably, a considerable number of major milestones among experimental achievements have been realized by using non-commercial devices, many of which were based on Hall sensors. The discovery of macroscopic quantum tunnelling and first order (melting) transition of the vortex lattice in superconductors are typical examples. The use of this technique by team 1 in its research on superconductivity has yielded a huge amount of expertise that allows us to recognize novel applications as well as shortcomings of the technique. The proposal has two goals: - Improvement of Hall sensor performance, and the fabrication of novel complex devices. - Exploration of new applications of Hall sensor magnetometry, mainly on nanometre scale objects. We benefit from the synergy of competences with team 3, specialized in semiconductor devices, and teams 1 and 2, users of magnetometry in frontline research. The interaction between our groups is already well established as testified by several co-signed publications. Partner 3 has also developped a close relationship with technology providers at the leading edge of III-V semiconductor technology. The pseudomorphic AlGaAs/InGaAs/GaAs (similar to pHEMT) MBE epiwafers grown Picogiga International for Itron include proprietary technology steps, which are not standard for the pHEMT products for RF applications. This allows the fabrication of QWHS with unmatched stability. The key advantage of Hall sensor devices is that their output is independent on the size of their active area. Within the present technology of a 2D electron gas confined within GaAlAs heterostructures, the sensitivity of a typical 10x10µm2 sensor is about 0.01 h/2e ( h/ 2e = Fo denotes a flux quantum of 2.07 10-15 Wb). Further reductions of the sensor size are possible and the target of our project is the realization of 0.5 x 0.5µm2 sensors without deterioration of other parameters. The paradigm of noise reduction and cancellation of resistive offsets has recently been proven by the group of V. Mosser (team 3). The realization of complex devices based on this principle is the second target of our project. The development of 'absolute' value magnetic field sensor, free of uncontrolled offsets is the key issue in most applications. The implementation of Hall sensors into scanning heads is another objective of the 'device' part of the present proposal. We wish to develop specific Hall sensor structures, incorporating an STM tip and a gradiometric sensor configuration. The second goal of our project consist the exploration of novel fields of applications of micro Hall sensor based magnetometers, which we briefly outline below. Recently, a new technique for the fabrication of nano-scale objects, template growth by electrodeposition in porous membranes, has been implemented at LSI (Ecole Polytechnique).. A large variety of submicron-sized samples has been obtained in well-controlled and reproducible way. At present, the only techniques for the exploration of the magnetic properties of those objects have been magneto-transport, and the large-scale deposition of nano-particles on arrays of micro-SQUID's (Superconducting QUantum Interference Devices). It is our goal to explore the magnetic properties of single nanoscale objects, as well as assemblies with a controlled density nano-objects by direct magnetization measurements, implemented by micro-Hall sensor magnetometry. This approach seems extremely promising when it comes to the characterisation of magnetization reversal in magnetic nanoparticles, which have drawn widespread interest due to their possible application in further downsizing of data storage devices. Other applications include the fabrication of novel junctions and switches using nanoscale superconducting wires interrupted by normal metallic or magnetic particles. Further applications in superconductivity concern the characterisation of new materials and the advancement of fundamental solid state physics. For example, the recent discovery of multi-gap superconductivity in MgB2 has opened the way to a new category of superconductors obtained by the doping of covalent orbitals. Among these, boron doped diamond is particularly interesting as superconductivity occurs in the vicinity of a metal-insulator transition. However, high-quality single crystals can only be synthesized on a micrometer scale. Hall-probe magnetometry is therefore a well-adapted technique for the study of the magnetic properties of such new systems.

Project coordination

Marcin KONCZYKOWSKI (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


Help of the ANR 175,000 euros
Beginning and duration of the scientific project: - 36 Months

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