Regensburg 2016 – scientific programme
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O: Fachverband Oberflächenphysik
O 84: Scanning Probe Techniques: Method Developments
O 84.12: Talk
Thursday, March 10, 2016, 18:00–18:15, S054
Application of Photothermal Expansion for Optical Absorption Mapping at the Nanoscale — •Teresa Isabel Madeira1, Raul David Rodriguez2, 3, Yuvaprasad Ravikumar2, Harsha Shah2, Eugene Bortchagovsky4, and Dietrich RT Zahn2, 3 — 1BioISI-Department of Physics-Faculdade de Ciencias-Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal — 2Semiconductor Physics-Technische Universität Chemnitz, D-09107 Chemnitz, Germany — 3cfaed-TU Dresden — 4V. Lashkarev Institute of Semiconductor Physics of NASU, pr.Nauki 41, Kiev 03028, Ukraine
We demonstrate photothermal expansion can be used to obtain images of nanostructured semiconductor materials such as GaSe flakes on graphite and carbon nanotubes on SiO2 in ambient conditions with high sensitivity and spatial resolution. The principle behind is the detection of the mechanical force exerted on an atomic force microscopy (AFM) tip by the thermal expansion of the materials excited with pulses of optical radiation, taking advantage of the different absorption properties between substrate and sample. Characterization of semiconductor nanostructures, with a bandgap in the optical range enables the use of cw lasers chopped and synchronized with the resonance frequency of custom-made fully metallic cantilever AFM Au tips. The spatial resolution achieved by the synchronization procedure described is indeed in the nanometer range below 60 nm, and by taking advantage of the difference between optical absorption and thermal coefficients material contrast can be achieved. The optimal conditions to make the most of this technique are also discussed.