Method micro-Raman

However, as Raman scattering is a two-photon process, the probability of the Raman scattering process is lower than that of fluorescence and IR absorption processes. The cross section of Raman scattering is 10 cm, which is much smaller than that of fluorescence ( 10 cm ) and IR absorption ( 10 °cm ). When we detect Raman scattering at the nanoscale, the number of photons obtained is less than with the usual micro-Raman spectroscopy due to reduction in the detection area or the number of molecules. To overcome this problem, we need to devise a method for amplification of Raman scattering. 

The vast identification potential of micro-Raman spectroscopy combined with the aforementioned sophisticated chemometric analysis methods is corroborated within various works In one study a total of 2257 Raman spectra of single cells were used to differentiate among 20 strains belonging to 9 different species. Here, a recognition rate of 89.2% for strains using the SVM technique could be achieved, albeit these bacteria were grown under different conditions (cultivation time medium, and temperature). [45]... 

Other methods include tip-enhanced Raman using 20- to 30-nm diameter Au or Ag tips, polarized Raman, stimulated Raman, micro-Raman spectroscopy, and coherent anti-Stokes Raman spectroscopy (CARS), where two laser beams are combined to generate an anti-Stokes beam, and so on. 

The final question is how to control the achieved materials. Methods and representative references are listed in Table 12.1. Two of these methods, the depthsensing indentation and the micro-Raman scattering, were developed recently and will be addressed in the last part of this chapter. 

Low-wavenumber Raman bands of MWCNT were assigned in terms of modes from coupling of radial breathing modes of individual tubes via van der Waals interactions.279 The Raman spectra of MWCNT prepared at 470°C showed the coexistence of graphite and amorphous carbon units.280 Micro-Raman spectra were used to characterise 13C-labelled MWCNT.281 The Raman spectra of MWCNT s subjected to plasma-etching were used to identify structural defects introduced thereby.282 Raman spectroscopy was used to compare the structures of MWCNT s prepared by high-temperature arc and low-temperature CVD methods. The former had a more graphite-like structure.283 Micro-Raman spectroscopy was used to characterise MWCNT obtained by electrophoretic deposition.284... 

Composition profiles generated by interdiffusion in the concentrated regime between polyphenylene oxide-polystyrene blend pairs were experimentally determined by two techniques. Three-point bending moment measurements over a convenient temperature range (dynamic mechanical analysis (DMA)) were used to determine interphase composition profiles. Confocal micro-Raman spectroscopy was also used to measure local compositions along a direction which was perpendicular to the original interface. The study included some limiting cases to test accuracy, precision and flexibility of the DMA method. 4 refs. 

PP-g-MA (0.1 mol% MA). Characterization methods included SEM, ESCA, and interfacial tension measurement. Tselios et al. (1998) have prepared compatibilized blends of LDPE and PP through inclusion of PP-g-MA (0.8 mol% MA) and EVAl (7.5 mol% vinyl alcohol). Blends were characterized using SEM, torque rheometry, mechanical properties, FTIR, and micro-Raman spectroscopy. 

Instead of performing imaging of a surface, various near-field spectroscopy methods can be applied to the study of corrosion, such as micro-Raman and surface-enhanced micro-Raman or other atomic and molecular microscopy techniques. 

Karavas E, Georgarakis M, Docoslis A, Bikiaris D (2007b) Combining SEM, TEM, and micro-Raman techniques to differentiate between the amorphous molecular level dispersions and nanodispersions of a poorly water-soluble drug within a polymer matrix. Int J Pharm 340 76-83 Karmwar P, Graeser K, Gordon KC, Strachan CJ, Rades T (2012) Effect of different preparation methods on the dissolution behaviour of amorphous indomethacin. Eur J Pharm Biopharm 80 459-464... 

The development of the technology for micro-Raman methods has been much more difficult than for traditional IR methods. What factors contribute to this difficulty ... 

As noted in previous sections, the development of life prediction models for the reliability of patterned features such as periodic lines on substrates inevitably requires knowledge of intrinsic stress and mismatch stress generated during film growth, patterning, passivation and service. In this section, three prominent experimental methods for determining stress in thin films with patterned lines are considered the substrate curvature method, the x-ray diffraction method, and the micro-Raman spectroscopic method. The advantages and limitations of each of these techniques are also briefly addressed. 

Micro-Raman spectroscopy has evolved as a possible experimental method for estimating local stress in nonplanar, submicron scale structures of interest in very large scale integration (VLSI) devices and MEMS see, for example, Kobayashi et al. (1990) and DeWolf et al. (1992). Examples of the geometries studied by this method include local isolation structures involving techniques such as local oxidation of polysilicon over silicon, iso-... 

A drawback of this method is that micro-Raman spectroscopy cannot generally be applied to metallic materials. Furthermore, stress estimation can only be made on the basis of Raman spectra gathered in the substrate and the dielectric on the sides of the interconnect lines. Such measurements cannot be made in the region immediately below the line, where the stress is more uniform and more sensitive to the stress in the lines themselves, if the substrate is nontransparent. Despite these limitations, the micro-Raman spectroscopy method has been successfully used to infer the average values of internal stress components in interconnect lines tested in the as-fabricated condition as well as after electromigration testing (Ma et al. (1995) DeWolf et al. (1999)). 

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