[PAST EVENT] Physics Colloquium
Bahram Roughani, Loyola University Maryland, Title of Talk: Raman scattering correlation with crystallographic orientation of Si cut off axis
Abstract: Raman spectroscopy is the inelastic scattering of light by matter, a process which provides important insight into the structure and properties of materials. This laser spectroscopy technique provides non-destructive and non-contact analysis with high spatial resolution up to sub-micron scale and requires no sample preparation. Raman scattering of solids represent vibrational modes that are directly linked to the crystal symmetry. Therefore, intensity analysis of Raman modes provides information about crystal properties. We have leveraged this characteristics to develop a new approach in polarized backscattered Raman spectroscopy that can identify the crystallographic orientation of silicon cut off axis. Our theoretical model is developed using Raman tensors for backscattering geometry that predicts variations in the backscattering polarized Raman intensity profiles as a function of the rotating wafers about the lab z-axis. A comparison between the experimental spectra and theoretical model will be presented, and specific Raman spectra signatures that are correlated with the degree of off-axis cut for single crystals of Si wafers will be discussed. Our model suggests a quick and nondestructive approach for determining the off-axis cut of single crystal Si wafers, which is the most commonly used substrate material in semiconducting device fabrications.