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Nanomechanical Raman Spectroscopy
There are several existing experimental methods to measure stress distribution at small scale such as X-ray diffraction (XRD) and cross-sectional transmission electron microscopy (XTEM) etc.. Raman spectroscopy method to measure the stress was first introduced by Anastassakis et al. in 1970 to measure the mechanical stress inside silicon. From then on, this method has been used and developed extensively to investigate stress distribution in silicon structures. Compared to the other available methods for stress measurement, Raman spectroscopy method is a non-destructive technique, requires minimal sample preparation, and has spatial resolution of less than one micron that makes it suitable for microscale to nanoscale resolution measurements in mesoscale and higher length scale samples. Most importantly, this method is also suitable for the measurement of temperature and thermal conductivity along with stress.
Nanomechanical Raman Spectroscopy (NMRS) [1-6] is a novel nondestructive and non-contact method to measure the stress in a substrate at sub-micron scale as a function of applied load without a need to measure strains in contrast to X-ray diffraction based experiments that measure strain. Another benefit of NMRS is that the use of Raman spectroscopy principles allows one to critically examine the influence of chemical factors such as corrosion. Therefore, NMRS has become a promising tool for stress measurements at the microscale where the strain to stress conversion relation is not clear as a function of change in chemical environments.
Zhang, Y., M. Gan, and V. Tomar, Raman thermometry based thermal conductivity measurement of bovine cortical bone as a function of compressive stress. ASME Journal of Nanotechnology in Engineering and Medicine, 2014: p. 021003 (11 pages).
Zhang, Y., D.P. Mohanty, and V. Tomar, Visualizing in-situ Microstructure Dependent Crack Tip Stress Distribution in IN-617 Using Nano-mechanical Raman Spectroscopy. Journal of Materials, 2016. 68(11): p. 2742-2747.
Gan, M. and V. Tomar, Surface stress variation as a function of applied compressive stress and temperature in microscale silicon. AIP Journal of Applied Physics, 2014. 116: p. 073502 (10 pages).
Gan, M. and V. Tomar, Temperature dependent microscale uniaxial creep of silicon and surface dominated deformation mechanisms. ASME Journal of Nanotechnology in Engineering and Medicine, 2014. 5: p. 021004 (9 pages).