Nanoscale mapping of strain, composition and electronic structure in SiGe nano-stripes

High carrier mobility in MOSFET devices can be obtained by controlling the uniaxial strain of the channel [1,2] due to strain-induced warping of the Si and Ge electronic band structures [3]. This requires: (i) knowledge and control of the strain in the channel on the nanoscale, and (ii) understanding its effect on the electronic structure. We present an experimental study of misfit strain, elemental composition and electronic structure mapped down to the nanoscale by Tip Enhanced Raman Scattering (TERS) and Energy-Filtered X-Ray Photoelectron Emission Microscopy (XPEEM) of 150 nm lithographically defined SiGe nano-stripes on Si(001) substrate. During the TERS experiment we monitored the intensity and the frequency of the locally enhanced Si-Ge and Ge-Ge Raman modes across a single nano-stripe, giving the perpendicular strain profile with a lateral resolution of ~ 30 nm. The strain is tensile and becomes maximum (~ +1.4 %) at the center of the nano-stripe, decreasing close to zero at the edges. 3D Finite Element Modeling calculations are successfully compared to the experimental results. The XPEEM experiments were performed using the NanoESCA microscope with a lateral resolution better than 100 nm. We mapped the composition, work function and valence states contrast between the nano-stripes and the surrounding bulk Si. The strain-induced shift of the valence band maximum and modification of the valence band dispersion inside the nano-stripes are compared with first-principles calculations. [1] J. Xiang et al., Nature 441 (2006) 489. [2] H. Ko et al., Nature 468 (2010) 286. [3] S.Thompson et al., IEEE Transactions 53 (2006) 1010. 22/04/2011 Abstract preview http://