20 nm-Resolved Stress Profile in SiGe Nano-Stripes Obtained by Tip-Enhanced Raman Spectroscopy

In this chapter, we describe the determination of the stress profile in 150-nm-wide SiGe nano-stripes embedded into a Si matrix by using oblique incidence tip-enhanced Raman spectroscopy (TERS) with a spatial resolution of ~20 nm. The TERS spectra of the stripes exhibit a number of locally enhanced phonon modes that are absent when the tip is positioned out of the stripes. The hydrostatic stress component across the nano-stripe width is evaluated from the strain-induced frequency shift of the Si-Ge mode at ~380 cm -1. The stress magnitude is found to be largest in the nano-stripe center and decreases monotonously on each side down to zero at the boundaries. This behavior is quantitatively described by a classic continuous medium model. These results demonstrate the applicability of the TERS technique to stress determination in novel semiconductor structures at the nanometer scale.