Imaging of organic molecular films using a scanning near-field optical microscope combined with an atomic force microscope

Abstract

A scanning near-field optical microscope combined with an atomic force microscope is described. The instrument uses a microfabricated force-sensing cantilever made of single-crystal silicon with an integrated p-n diode at its end as a microphotodetector. The photosensitive cantilever efficiently detects the light scattered by the tip in the evanescent field generated by illuminating the sample by total internal reflection. Simultaneously the surface force is detected by monitoring the deflection of the cantilever. Both scanning near-field optical microscope and atomic force microscope images of a compact disk grating and a photosynthetic protein membrane were obtained. The membrane was deposited on the glass substrate using the Langmuir–Blodgett technique. The features in the scanning near-field optical microscope images are similar to those in the atomic force microscope. The possible crosstalk between the optical and the topography signal is discussed.