Raman strain measurement

C. Galiotis and J. Parthenios, Stress/strain measurements in fibers and composites using Raman spectroscopy, in Vibrational Spectroscopy of Biological and Polymeric Materials, V.G. Gregoriou and M.S. Braiman (Eds), CRC Press, Boca Raton, 2006. 

Ogura A, Yamasaki K, Kosemura D, Tanaka S, Chiba 1, Shimidzu R (2006) UV-Raman spectroscopy system for local and global strain measurements in Si. Jpn J Appl Phys 45 3007... 

Many other examples of stress or strain measurements through Raman spectroscopy are still primarily qualitative [18, 27]. Much of this stems from the fact that Raman spectroscopy provides only limited additional information (generally only in the form of frequency shifts) from potentially complicated strain distributions. Furthermore, care must be taken when extracting stresses from measured Raman shifts as key mechanical properties such as Young s modulus (which is related to the compliance or stiffness matrix elements) may be diameter dependent in NWs [61]. Still, Raman mapping with submicron spatial resolution and careful polarization analyses may help clarify the piezospectroscopic properties of semiconductor NWs in ongoing research. 

Galiotis, C., Laser Raman spectroscopy, a new stress/strain measurement technique for the remote and on-line non-destructive inspection of fiber reinforce polymer composites. Mater. TechnoL, 8, 203, 1993. 

Everall N, Lumsden J, Fundamental reproducibility of Raman band positions and strain measurements of high modulus carbon fibres—the effect of laser induced heating, J Mater Sci, 26, 5269, 1991. 

With a Raman instrument, measurement of these low lying bands is fairly straightforward. If the elastic Rayleigh scattering can be removed (for example the use of iodine gas filters (56) to selectively absorb the Rayleigh line), very low frequency vibrations in the range of a few cm can be observed. Based on the imit cell parameters of polyethylene, a set of Raman active lattice vibrations has been observed for polyethylene and paraffins (57). Rotatory modes are seen in traras-l,4-polybutadiene (49). With analysis of these low lying vibrations in a quantitative fashion, a correlation between molecular and macroscopic properties such as heat capacity, thermal pressure, thermal expansion, P-V-T relations, and stress-strain behavior can all be established (58). 

Fig. 11 a) Experimental setup used for uniaxial strain measurements b) Raman spectra of graphene with increasing strain. Adapted from Ref 85. 

S Nakashima, A Fujii, K Mizoguchi, A Mitsuishi, K Yoneda. Raman-scattering measurements of strains in ZnSe epitaxial-films on GaAs. Jpn J Appl Phys 27 1327-1330, 1988. 

Figure 8.12 shows the distribution of strain along a single Kevlar 149 fibre in a model single-fibre epoxy composite [38] calculated from the point-to-point variation of the shift of the 1610cm aramid Raman band. Measurements were taken at 20 pm intervals along the fibre for different levels of matrix strain e ranging from 0% to 2.0% in intervals of 0.4%, and the curves drawn are best fits to the experimental data. It can be seen that in the unstrained case (e = 0%) there is no strain in the fibre. As increases the strain in the fibre increases from... 

Raman Microspectroscopy. Raman spectra of small soflds or small regions of soflds can be obtained at a spatial resolution of about 1 p.m usiag a Raman microprobe. A widespread appHcation is ia the characterization of materials. For example, the Raman microprobe is used to measure lattice strain ia semiconductors (30) and polymers (31,32), and to identify graphitic regions ia diamond films (33). The microprobe has long been employed to identify fluid iaclusions ia minerals (34), and is iacreasiagly popular for identification of iaclusions ia glass (qv) (35). 

More recently, Raman spectroscopy has been used to investigate the vibrational spectroscopy of polymer Hquid crystals (46) (see Liquid crystalline materials), the kinetics of polymerization (47) (see Kinetic measurements), synthetic polymers and mbbers (48), and stress and strain in fibers and composites (49) (see Composite materials). The relationship between Raman spectra and the stmcture of conjugated and conducting polymers has been reviewed (50,51). In addition, a general review of ft-Raman studies of polymers has been pubUshed (52). 

Physical Properties. Raman spectroscopy is an excellent tool for investigating stress and strain in many different materials (see Materlals reliability). Lattice strain distribution measurements in siUcon are a classic case. More recent examples of this include the characterization of thin films (56), and measurements of stress and relaxation in silicon—germanium layers (57). 

Wright of Advanced Micro Devices discusses the use of Raman microspectroscopy to measure the integrity of a film on semiconductor wafers during manufacture in US patent 6,509,201 and combined the results with other data for feed-forward process control [181]. Yield is improved by providing a tailored repair for each part. Hitachi has filed a Japanese patent application disclosing the use of Raman spectroscopy to determine the strain in silicon semiconductor substrates to aid manufacturing [182]. Raman spectroscopy has a well established place in the semiconductor industry for this and other applications [183]. 

Enabled by the high resolution of spectra, which is enhanced by the use of spatial filter assembly having a small (200 pm) pin hole, the principle of the strain-induced band shift in Raman spectra has been further extended to the measurement of residual thermal shrinkage stresses in model composites (Young et al., 1989 Filiou et al., 1992). The strain mapping technique within the fibers is employed to study the... 

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