PhotoThermal Induced Resonance. Application to Infrared Spectromicroscopy

In this chapter, we shall describe a new technique for carrying out infrared spectromicroscopy at the nanoscale. This technique is based on the detection of expansion, induced by the photothermal effect, by the cantilever of an atomic force microscope (AFM). We begin by explaining the advantages of studying matter in the infrared frequency range, and the limits of conventional techniques. We then describe the underlying principles and the setup we have developed for going beyond these limits. We present a simple theoretical approach to the relevant phenomena in order to bring out the intrinsic properties of this method, and we discuss in particular the question of resolution. To end our discussion, we illustrate the potential of the PTIR technique by some experimental results.