Highly efficient tip-enhanced Raman spectroscopy and microscopy of strained silicon.

We present a versatile tip-enhanced Raman spectroscopy (TERS) system that permits efficient illumination and detection of optical properties in the visible range to obtain high signal-to-noise Raman signals from surfaces and interfaces of materials using an edge filter. The cutoff wavelength of the edge filter is tuned by changing the angle of incident beam to deliver high incident power and effectively collect scattered near-field signals for nanoscopic investigation in depolarized TERS configuration. The dynamic design of the instrument provides a unique combination of features that allows us to perform reflection or transmission mode TERS to cover both opaque and transparent samples. A detailed description of improvements of TERS was carried out on a thin strained silicon surface layer. The utilization of an edge filter for shorter collection time, specialized tip for higher field enhancement and for elimination of Raman signal from the tip, shorter wavelength, sample orientation relative to probing polarization, and depolarized configuration for higher contrast Raman signal is discussed.