Experimental challenges for approaching local strain determination in silicon by nano-Raman spectroscopy

Raman intensity enhancement induced by nanoprobes (metal particles and metallised tips) approached to a strained silicon sample surface is reported. With silver nanoparticles deposited onto a silicon surface, high enhancements in the vicinity of particles were observed. Furthermore, metallised tips were scanned inside the spot of the laser used for Raman measurements. Both silver-coated and pure silver tips, mounted onto a tuning fork, indicated high Raman signal enhancement for optimised tip position within the laser spot. Atomic force microscopy was performed on a structured sample to investigate the stability of these tips. Focused ion beam was utilized to refine and to re-sharpen pure silver tips after the measurements. Complementary measurements were performed using pure tungsten tips. Due to the high hardness of W wires, a special pre-etching technique was applied in this case.