Theory And External Optical System For Accurate Measurement Of Experimental Mechanics By Using Raman Spectroscopy

Micro-Raman spectroscopy was regarded as an effective method of mechanical measurement in micro-scale because of its special advantages such as high spatial resolution,non-destructive,and sensitive to the intrinsic stress.In recent years,a series of achievements had been achieved about the theoretical and applied studies of Ramanmechanical measurements.However,there was still a lack of fundamental investigation for the accurate and or precise mechanical measurement by using Raman spectroscopy.For instance,superficial,typical and simplified Raman-mechanical models were always used in the analyses of cross-section,atypical or complicated materials(or structures),leading to inaccurate and even false stress/strain results.Meanwhile,there was no available component,neither relative potential,applying well-controlled mechanical loading in currently universal Micro-Raman system.Therefore,this paper presented a methodological work about the theory and external optical system for the accurate measurement of experimental mechanics by using Raman spectroscopy.A general model of Raman-mechanical relationship was achieved for arbitrary lattice plane in crystalline silicon according to the generalized Hooke laws,the frequencystrain relationships and the Raman selection rules.The model was applied by taking some orientations such as(100)(110)and(111)as examples,educing the detailed wavenumber-stress equations suitable for accurate Raman-mechanical measurement along these crystal orientations under different stress states.Then,?-Si/Ge0.2Si0.8/Gex Si1-x/C-Si heterostructure was investigated using Raman spectroscopy experiments.The distribution of residual stress along the depth of the multi-layer heterostructure was determined by using the more accurate Raman-mechanical model.An independent external optical system of Micro-Raman spectroscopy(EOS-MRS)was established and then coupled with a universal Raman system(Renishaw In Via Reflex)and a mechanical loading device successfully.The EOS-MRS was composed by two co-axial light paths.The observation path was used to illuminate and view the specimen with white light for selecting required sampling spot,similar to an optical microscope.The laser path is used to excite and collect Raman signals through optical fibers.An calibration experiment was carried out on Kevlar29 fiber by using the coupled systems(EOS-MRS,Renishaw In Via Reflex and mechanical loading device).The results proved that the EOS-MRS can effectively extend the application of Ramanmechanical measurement under complex loading.