TIPTOP

Mastering heat transfer in micro and nanoscale materials or devices has become crucial, in particular due to increasing thermomechanical issues and the dependence of many phenomena involving an Arrhenius-type law on local temperature. Despite sustained effort over the two last decades to reach this objective, local thermal characterization at the nanoscale remains a challenge. Scanning Thermal Microscopy (SThM) is a technique derived from Atomic Force Microscopy (AFM) where a thermal sensor is located on the probe. This technique is expected to allow for sub-100 nm spatial resolution. However, the cost to reach such a spatial resolution is usually that the sensitivity of the thermal measurement is not as good as for other techniques. The TIPTOP project is a 4-year collaborative project aiming at (i) developing a new resistive SThM probe for nanoscale quantitative thermal measurement, (ii) demonstrating the capabilities of the new technique on application-oriented micro and nanostructured materials and systems, (iii) developing an optimized technological French industrial solution. The solution proposed in TIPTOP is based on the following novelties: (a) the use of a unique type of resistive thermometry using niobium nitride, which has been shown to possess a temperature coefficient of the electrical resistivity (thermal sensitivity) 5 to 10 times higher than competitors, will allow for a strong improvement of the capabilities of SThM. (b) A proper design of the SThM cantilever can also lead to an improvement of SThM, since currently-available cantilevers have not been optimized at all, which results in huge (>95%) thermal losses in SThM probes. (c) The electronics associated to the electrothermal measurements required by thermal characterization can be miniaturized, located closer to the tip, therefore becoming more reliable than solutions available up to now. In addition, SThM is currently a complicated technique with almost no efficient calibration setup and it requires long learning process which often discourages the potential user. In this project, (d) two channels will be followed to remedy this drawback. A set of nanometer-scale active thermal devices based on the electronics technology will be fabricated to facilitate the calibration of the technique. In addition, showcases involving world-class nanomaterials will demonstrate the potential of the TIPTOP SThM solution. All the work is subtended by acknowledging that nanoscale thermal transport is an open field where many novel physical phenomena can be observed, involving e.g. ballistic transport, Kapitza resistances, adsorbed menisci or near-field thermal radiation. Novel scientific results on these topics are possible only if a strong improvement in the thermal sensitivity is demonstrated. Some results are targeted as an output of TIPTOP. To reach its objectives, the project consortium gathers three academic research laboratories with complementary expertise in SThM, nanothermal modelling, resistive nanothermometry, instrumentation, metrology and micro and nanofabrication, and one industrial partner strongly involved in the development and manufacturing of Scanning Probe Microscopy (SPM) instruments. The outputs of TIPTOP will be embodied in (a) the highly-sensitive SThM along with the necessary new instrumentation and (b) the showcase of demonstration on specimens that will be developed to maximize impact through dissemination and exploitation.