Spectroscopy spectroscopic ellipsometry

Diffusion in polymer-polymer systems is important in many practical applications, such as crack healing, polymer blending, welding, adhesion, elastomer tack, polymer fusion, and many others. However, diffusion coefficient data is lacking due to the complexity of the polymer diffusion process. Typical techniques employed are infrared spectroscopy, spectroscopic ellipsometry, and optical schlieren. Only a few studies of interdiffusion in polymer pairs are reported. Depending on the temperature and other physical parameters of the system, Fickian and Case II diffusions (see Section 4.3) can be observed with varying relative importance (Jabbari and Peppas, 1993). 

Amongst other spectroscopic teclmiques which have successfiilly been employed in situ in electrochemical investigations are ESR, which is used to investigate electrochemical processes involving paramagnetic molecules, Raman spectroscopy and ellipsometry. 

The film thickness and retractive index were calculated using spectroscopic ellipsometry. X-ray photoelectron spectroscopy (XPS) was used for composition analysis. Auger electron spectroscopy (AES) and secondary ion mass spectroscopy (SIMS) was used to investigate the depth profiles of the film. 

Spectroscopic ellipsometry is a non-destructive, interface sensitive, in situ technique for interface characterization. Time resolved ellipsometric spectroscopy was used to determine the mechanism of electrochemical deposition of photoresists on copper electrodes under potentiostatic, anodic conditions. Nucleation of photoresist deposition occurs randomly. During the early stages of nucleation the semi-spherical particles are separated by about 100 A. The deposits tend to grow like "pillars" up to 50 A. Further growth of the "pillars" lead to coalescence of the photopolymer deposits. 

An ozone treatment (10 minutes at room temperature) of the HF-etched SiC surface before the metallization step was introduced as a very convenient processing step to produce Schottky diode gas sensors with an increased stability and reproducibility. The use of spectroscopic ellipsometry analysis and also photoelectron spectroscopy using synchrotron radiation showed that an oxide, 1-nm in thickness, was formed by the ozone exposure [74, 75]. The oxide was also found to be close to stochiometric SiO in composition. This thin oxide increased the stability of the SiC Schottky diodes considerably, without the need for any further interfacial layer such as Ta or TaSi which have been frequently used. Schottky diodes employing a porous Pt gate electrode and the ozone-produced interfacial layer have been successfully operated in both diesel exhausts and flue gases [76, 77]. 

To obtain the morphology information, including phase separation and crystalline, we can now use microscopic techniques, atomic force microscopy, transmission electron microscopy, electron tomography, variable-angle spectroscopic ellipsometry. X-ray photoemission spectroscopy, and grazing-incidence X-ray diffraction. The detailed information of this characterization methods can be found from the specific reference (Li et al., 2012 Huang et al., 2014). 

Spectroelectrochemistry encompasses a group of techniques that allow simultaneous acquisition of electrochemical and spectroscopic information in situ in an electrochemical cell. A wide range of spectroscopic techniques may be combined with electrochemistry, including electronic (UV-visible) absorption and reflectance spectroscopy, luminescence spectroscopy, infrared and Raman spectroscopies, electron spin resonance spectroscopy and ellipsometry. Molecular properties such as molar absorption coefficients, vibrational absorption frequencies and electronic or magnetic resonance frequencies, in addition to electrical parameters such as current, voltage or charge, are now being used routinely for the study of electron transfer reaction pathways and the fundamental molecular states at interfaces. In this article the principles and practice of electronic spectroelectrochemistry are introduced. 

The optical phonon spectrum is one of the most fundamental characteristics of the crystals. It reflects the specific features of the interatomic interactions and gives very comprehensive and detailed information about the thermal and optical properties involving the efficiency of the optoelectronic devices. The vibrational properties in all the nitride systems have heen investigated in detail over the years by Raman scattering (RS) spectroscopy. Recent studies of nonpolar a-plane GaN by RS confirmed the finding in the c-plane GaN [107, 108]. However, in some cases there is a lack of agreement between the values of some phonon deformation potentials and strain-free phonon-mode positions in GaN and AlN, as determined theoretically and by employing RS spectroscopy. The nonpolar materials allow an access to the complete set of phonons by infrared spectroscopic ellipsometry (IRSE). This provides an alternative tool to study the vihrational properties and to establish very important and useful fundamental parameters of the nitrides. 

Scheme 9.1 Methods in morphology characterization. TEM transmission electron microscopy EF-TEM energy filter transmission electron microscopy STXM scan transmission X-ray microscopy GISAXS grazing incidence small-angle X-ray scattering SANS small-angle neutron scattering RSoXS resonant soft X-ray scattering SEM scanning electron microscopy DSIMS dynamic secondary ion mass spectroscopy XR X-ray reflectivity NR neutron reflectivity VASE variable angle spectroscopic ellipsometry.

Bundesmann, C. (2005) Phonons and plasmons in ZnO-based alloy and doped ZnO thin films studied by infrared spectroscopic ellipsometry and Raman scattering spectroscopy, PhD Thesis, Universitat Leipzig (Shaker, Aachen, 2006). 

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