Contrast enhancement on crystalline silicon in polarized reflection mode tip-enhanced Raman spectroscopy

Tip-enhanced Raman spectroscopy in reflection mode makes possible the nanoscale characterization of non-transparent samples, such as silicon, inaccessible in transmission mode. However, a particular feature of this technique is the superposition of the far-field Raman signal with the near-field one generated in the tip vicinity sometimes resulting in a low near-field-to-far-field contrast. By using a polarized configuration and orientation optimization of a (0 0 1) crystalline Si sample we were able to enhance significantly the contrast through reducing the far-field contribution, reaching a value of about 40. This contrast enhancement method can be applied in principle to any crystalline sample.