Nanoscale characterization of localized strain in crystals by tip-enhanced Raman spectroscope in reflection-mode

摘要

Nanoscale characterization of strained silicon is essential for developing reliable next generation integrated circuits. Vibration mode of Si-Si in strained silicon was selectively enhanced to be observed by surface enhanced Raman spectroscopy technique. Covering the silver island film on a strained silicon layer Raman signal from the strained silicon can be detected with a high sensitivity against the overwhelming background signal from the underlying silicon layer. This technique allowed us for micro-Raman spectroscopy on strained silicon, and is straightforward to nano-Raman spectroscopy by tip-enhanced Raman microscope in which a sharpened metallic tip is used instead. We observe localized strains in strained silicon by tip-enhanced near-field Raman spectroscope in reflection-mode. The tip-enhanced Raman spectra show that the Raman frequency and intensity of strained silicon were different within a Crosshatch pattern induced by lattice-mismatch. Micro Raman measurements, however, show only uniform features because of averaging effect due to the diffraction limit of light.