Instrumentation and Measurement Physics(DIMP)
Physique des instruments et mesures (DPIM)
Jean-Stéphane ANTONIOW
Reims University, Reims
(Photo)Thermal Imaging Using a Modified Atomic Force Microscope (AFM) Combined with Pyroelectric Detection
A variety of scanning probe microscopy techniques have been explored since the invention of the scanning tunneling microscope and of the atomic force microscope. Variants of these techniques include the scanning thermal microscopy (SThM) and the scanning near-field optical microscopy (SNOM). In the field of photothermal investigations, we attempted to achieve sub-micron-imaging resolution by combining a localized excitation provided by SNOM or SThM with a pyroelectric (PE) sensor in a back-detection configuration. The PE signal measured when the tip is "in contact" with the sample contains several thermal components. The main one is due to heat conduction from the tip right through the contact point. So, the PE signal accounts for the thermal wave propagating across the sample, which carries information on the thermal diffusivity. In the case of SNOM, optical properties at the sample surface may contribute to PE signal formation and the resolution is limited by the size of the optical fibre aperture. Our aim was to map thermal diffusivity in the case of very thin layered samples deposited on a PE sensor used as substrate. We show that spatial integration of thermal effects by the PE sensor allows the use of a simple one-dimensional geometry for the theoretical analysis of several operating modes. Images of PE signals reveal contrast zones due to variations of thermal properties, in particular of the thermal diffusivity of a test sample. The method may open new perspectives for thermal investigations of thin layers in biological or technological domains at a microscopic scale.
In Collaboration with Mihai Chirtoc*, Franck Lei* Nathalie Trannoy*, Josef Pelzl**, (*) Unité de Thermique et Analyse Physique, Reims University, Reims, France, (**) Exp. Phys. III, Solid State Spectroscopy, Ruhr-Universität, Bochum, GERMANY