Local eletrical measurements by intermittent contact AFM - Applications to molecular spintronics and industrial transfer - – MELAMIN

Local electrical measurements by atomic force microscopy (AFM) have become an indispensable tool, as much for the characterization of materials, structures and devices at an increasingly reduced scale, as for the more fundamental properties studies of nanostructures and nano-objects. This is the reason why the consortium partners (LGEP, UMPhy CNRS-Thales, CSI) proposed, as part of the 2006 National Nano initiative call, a project focused on a breakthrough instrument (the "Résiscope") to achieve local electrical resistance imaging in contact mode over a very wide resistance range (“ALICANTE” project, ANR-06-NANO-064). Completed in September 2010, this project has fully achieved all of its three objectives: the instrumental performance of the device has achieved more than 11 decades (which is unique at the worldwide scale); a novel application of Sub -10nm nanolithography has been developed, giving rise to several studies of top quality research (Garcia, Nature 2009; A. Bernand Mantel Nature Phys. 2009; Ruotolo Nature Nano. 2009; C. Barraud Nature Phys. 2010); and finally the development of a robust commercial version has led to the successful commercialization of the instrument in late 2009. The national research agency has praised a project that "provides a benchmark for scientific and industrial transfer” in its final assessment.

Even if the extreme sensitivity of the Résiscope enables its operation with very low tip/surface contact force, this force is applied continuously throughout the scan (contact mode) which can easily damage soft samples. The main objective of this new project is to modify the Résiscope unit in order to work in intermittent contact mode. This would allow a consequent broadening of its range of applications to soft materials (molecular electronics, biology ...) and fragile or weakly anchored nano-objects for which there is an increasingly high demand for local electrical characterizations. This goal is far beyond a simple performance improvement: it is a thorough review of the principles of the instrument, allowing its adaptation to radically different and far more complex operating conditions.

In continuation of our precedent project's philosophy, this project focuses on three areas: a strong instrumental development at the heart of the project led by the LGEP (partner 1 and coordinator) coupled with constant feedback to an ambitious application axis centered on advanced research on molecular materials carried by the UMPhy (partner 3) and an axis of development driven by TPE CSI (partner 2). All this will be pursued in a highly competitive and rapidly changing environment such as near-field microscopy. An optimized Résiscope module for the intermittent mode will be first obtained by a succession of changes to the current module Résiscope (LGEP). Following these developments, the various key points in designing a new module dedicated to the measurements in intermittent mode will guide the development of a new IC-module Resiscope (Intermittent Contact Resiscope). This will be the key innovativation of the project. The obtained technology will then be transferred to CSI towards a successful prototyping of the integrated modules. These prototypes will enable a quick realization of commercial versions. Throughout the project, feedback will be provided and the instrumental developments will be validated by tests conducted in partnership with the UMPhy on both specifically made reference samples (ultra-thin molecular layers) and molecular spintronics research samples. The "research" grade samples by the UMPhy will broaden the assessment of the instrumentation and allow progresses leading to top level scientific advances.