Toward Robust High Resolution Chemical Imaging

Resonant plasmon excitations at the surface of noble metals can localize and amplify an electromagnetic field in a very small volume and are the enabling element of surface enhanced optical microscopies [1]. Tip enhanced Raman spectroscopy (TERS) combines scanning probe microscopy (SPM) with Raman spectroscopy, taking advantage of this enhancing mechanism [2]. So far a 20 nm lateral resolution in chemical imaging of a surface has been achieved. Unfortunately, pure noble metal nanostructures, the most active plasmon materials known, are fragile, and prone to mechanical, chemical, and morphological degradation (Fig 1). Means of protecting and extending the lifetime of these surfaces are key for making the plasmon-based high resolution chemical imaging a robust characterization technique.