Spring constant of an AFM cantilever with a thin-film plasmonic waveguide formed at its end

Abstract

Abstract Atomic-force-microscope (AFM)-based tip-enhanced Raman spectroscopy (TERS) is a promising analytical technique that can identify the physical and chemical properties of a sample’s surface. In the conventional TERS setup, the tip is directly irradiated by an incident light, which causes degradation of the contrast of the TERS signal due to the Raman scattered light from the surface area around the tip. We recently developed an AFM cantilever for indirect illumination AFM-TERS by milling the tip of the conventional cantilever to form a thin-film waveguide. Since the thin-film waveguide is considered as another cantilever attached at the end of the original cantilever, the waveguide cantilever can be treated as cantilevers connected in series. We then analyzed the static spring constant of the waveguide cantilever by both analytical and numerical methods and found that the static spring constant of the waveguide cantilever is lower than that of the original cantilever, which is advantageous in reducing the contact damage during the TERS measurements. We also proposed procedures to experimentally calibrate the static spring constant of the waveguide cantilever.