G. Ulrich, E. Pfitzner, A. Hoehl, J.-W. Liao, O. Zadvorna, G. Schweicher, H. Sirringhaus, J. Heberle, B. Kastner, J. Wunderlich, D. Venkateshvaran, Thermoelectric nanospectroscopy for the imaging of molecular fingerprints, Nanophotonics | Volume 9: Issue 14

We present a nanospectroscopic device platform allowing simple and spatially resolved thermoelectric de- tection of molecular fingerprints of soft – materials. Our technique makes use of a locally generated thermal gradient converted into a thermoelectric photocurrent that is read out in the underlying device. The ther- mal gradient is generated by an illuminated atomic force microscope tip that localises power absorption onto the sample surface. The detection principle is illustrated using a concept device that contains a nanos- tructured strip of polymethyl methacrylate (PMMA) defined by electron beam lithography. The platform’s capabilities are demonstrated through a comparison between the spectrum obtained by on-chip thermo- electric nanospectroscopy with a nano-FTIR spectrum recorded by s-SNOM at the same position. The sub-wavelength spatial resolution is demonstrated by a spectral line scan across the edge of the PMMA layer.