Highly efficient heating assisted tip-enhanced Raman spectroscopy

摘要

We present a tip-enhanced Raman spectroscopy (TERS) system that permits efficient illumination and detection of optical properties in the visible range to obtain high contrasts Raman signals from strained silicon (c-Si) assembled on silicon germanium substrate using an edge filter. The cut-off 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 a depolarized TERS configuration. We overshadow strong far-field background signals from Raman active materials by utilizing the results obtained from depolarized surface-enhanced Raman scattering experiments in conjunction with silicon Raman tensor calculation to quantify which polarizer, analyzer and sample azimuth combination gives the minimum far-field signals. Here, we utilize the s-polarization instead of p-polarized light in conjunction with polarization properties of c-Si to obtain a high contrast Raman signal. We found that for imaging Raman active and bulk crystalline materials such as silicon, background signal suppression (s-illumination) is more important than the field enhancement with strong far-field signal levels (p-polarization). The utilization of an edge filter for shorter collection ti me, depolarized configuration for higher contrast and tip heating for higher resolution are discussed.