Scanning nano-Raman spectroscopy of semiconducting structures

Tip-enhanced Raman spectroscopy (TERS) using side illumination is a promising spectroscopic tool for nanoscale characterization of chemical composition, structure, stresses and conformational states of non-transparent samples. Recent progress has shown signal enhancements for a variety of samples, including break-through enhancements of semiconductors. In this work, optimization of the polarization geometry increases contrast between near-field and far-field signals on Si and improves imaging quality. Two-dimensional images of semiconductor nanostructures show reasonable agreement between topographical and TERS images. These recent TERS results using both silver- and gold-coated tips demonstrate localization of the Raman enhancement to within approximately 20 nm of the tip. Also, the enhanced Raman signal of a strained Si layer is separated from an underlying Si substrate, which is encouraging for potential strain distribution analysis of silicon nanostructures.