Micro-Raman measurements

In Figure 3 is shown the experimental set-up used for micro-Raman measurements. 

Raman microscopy was developed in the 1970s. Delhaye (34) in 1975 made the first micro Raman measurement. Simultaneously, Rosasco (35, 36) designed a Raman microprobe instrument at the National Bureau of Standards (now the NIST). This early work established the utility of Raman spectroscopy for microanalysis. The technique provides the capability of obtaining analytical-quality Raman spectra with 1 pm spatial resolution using samples in the picogram range. Commercial instruments are available. 

The physical mechanisms associated with the phase transition of y-Fe203 nanoparticles induced by laser irradiation have been studied by El MendUi et al., by performing in situ micro-Raman measurements of both as-prepared y-Fe203 nanoparticles (about 4 nm in size) as a function of laser intensity and annealed samples [51]. Raman spectrum for the as-prepared nanoparticles showed the presence of three broad peaks at 350, 500, and 720 cm and magnon mode in the neighborhood of 1,300 cm . Such a Raman spectrum obeys the symmetry rules established for the inverse spinel structure with a tetragonal sublattice distortion,... 

Recently, it has been demonstrated that confocal Raman microscopy can be employed to obtain information on the phase, growth direction and radial crystallographic orientation of GaN nanowires [46, 47]. Fan et al. have demonstrated the orientation-dependent micro-Raman measurements on single wurtzite CdS nano wires with an average diameter of 60 nm [48]. The Raman spectra of nanowires were compared with those of bulk ribbon. As opposed to the Raman spectra fi om the bulk samples, the intensity of most Raman bands of the nanowires exhibited significant dependence on the polarization of the excitation with respect to the nanowire axis. The Raman bands were found to be polarized along the longitudinal axis because of the shape-induced depolarization effect, similar to... 

The advantages of micro-Raman measurements for such investigations were discussed in sect 5.5. We mention here that not only macroscopic but partly mesoscopic statistics of the distributions of phases as a function of the dopant become available. 

Dressier and Mastai studied the enantioselective crystallization of glutamic acid on self assembled monolayers of cysteine (Dressier and Mastai, 2007). The chiral SAMs were prepared by immersing gold covered glass slides in aqueous solutions of cysteine (lOmM) for 2 hours. These SAMs were then characterized by X-ray diffraction, micro-Raman measurements. X-ray photoelectron spectroscopy, contact angle and ellipsometry. 

Made et al. (2005) designed an electrochemical cell for in situ micro-Raman measurements on the polymer membrane of an operating PEMFC. The method is applicable to studies of both the distribution of water and membrane structure in the working cell environment. It was shown that a hydration profile with a lower water content at the anode forms when current is applied to the ceU. In addition, the overall liquid water content in the membrane decreases with increasing current, possibly as a result of an increase in cell temperature. 

Except for IR test, micro-Raman measurement was also used to determine the structure or structure change of aliphatic PEMs. A typical candidate is the use of micro-Raman spectroscopy to analyze the structure change of PVA after introducing HAP or MMT, and the increase in amorphous domains of the composite membranes was demonstrated [23,26]. Besides, micro-Raman spectroscopy has also been used for the confirmation of the existence of ionic groups (-SOj") and in particular for the degradation of PEMs after fuel cell tests [14,64]. 

In Raman measurements [57], the 514-nm line of an Ar+ laser, the 325-nm line of a He-Cd laser, and the 244-nm line of an intracavity frequency-doubled Ar+ laser were employed. The incident laser beam was directed onto the sample surface under the back-scattering geometry, and the samples were kept at room temperature. In the 514-nm excitation, the scattered light was collected and dispersed in a SPEX 1403 double monochromator and detected with a photomultiplier. The laser output power was 300 mW. In the 325- and 244-nm excitations, the scattered light was collected with fused silica optics and was analyzed with a UV-enhanced CCD camera, using a Renishaw micro-Raman system 1000 spectrometer modified for use at 325 and 244 nm, respectively. A laser output of 10 mW was used, which resulted in an incident power at the sample of approximately 1.5 mW. The spectral resolution was approximately 2 cm k That no photoalteration of the samples occurred during the UV laser irradiation was ensured by confirming that the visible Raman spectra were unaltered after the UV Raman measurements. 

The lateral surfaces of the samples were polished to allow micro-Raman profiling measurements. 

W. Schabel, I. Ludwig and M. Kind, Measurements of concentration profiles in polymeric solvent coatings by means of an inverse confocal micro Raman spectrometer - Initial results. Drying Technol., 22, 285-294 (2004). 

Wright of Advanced Micro Devices, Inc. discusses the use of Raman spectroscopy to measure the integrity of a film on semiconductor wafers during manufacture in US patent 6,50 9,201.87 The Raman measurements are made during the manufacturing process and can be considered an on-line system. Unlike many process Raman installations, this one is based on micro-Raman, where a microscope is used to focus the laser beam to a spot only a few micrometers in diameter. The Raman data is combined with other measurements, such as scatterometry, to calculate a stress level and compare it to... 

Raman CV, Krishnan KS (1928) A new type of secondary radiation. Nature 121 501-502 Ferraro JR, Nakamoto K (1994) Introductory Raman spectroscopy. Academic, Boston Gouadec G, Coiomban P (2007) Raman spectroscopy of nanomaterials how spectra relate to disorder, particle size and mechanical properties. Prog Cryst Growth Ch 53 1-56 Sourisseau C (2004) Polarization measurements in macro- and micro- Raman spectroscopies molecular orientations in thin films and azo-dye containing polymer systems. ChemRev 104 3851-3891 Rayleigh L (1879) Phil Mag 8 261... 

Dietrich B, Dombrowski KF (1999) Experimental challenges of stress measurements with resonant micro-Raman spectroscopy. J Raman Spectrosc 30 893-897... 

The Raman spectra on solid metal substrates were measured using a Renishaw RM2000 micro-Raman apparatus, coupled with a diode laser source emitting at 785 nm. Sample irradiation was accomplished using the 50x microscope objective of a Leica microscope DMLM. The beam power was 3 mW, the laser spot diameter was adjusted between 1 and 3 pm. Raman scattering was filtered by a double holographic notch filter system and collected by an air-cooled CCD detector. The acquisition time for each measurement was 10 s. All spectra were calibrated with respect to a silicon wafer at 520 cm. ... 

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