Spectroscopy of thin films

Alexander V. Khomchenko, Waveguide Spectroscopy of Thin Films, Volume 33, 2005. 

The direct mapping of the electronic structure of the conjugated polymers is possible in photoelectron spectroscopy of thin films. The valence band, which is available from ultraviolet photoelectron spectroscopy, clearly shows shifts as well as a reduction of photoelectron peaks coming from the frontier k orbitals [31—33]. This is consistent with predictions from calculations using a Valence Effective Hamiltonian using a model of conformational twists separating every dimer on the chain. 

Hartmann, A.J., Lamb, R.N., 1997. X-ray photoemission spectroscopy of thin films. Cmr. Opin. Solid State Mater. Sci. 2, 511—516. 

Lind, A.H.N., Wilson, J.I.B., Mather, R.R., 2011. Raman spectroscopy of thin-film silicon on woven polyester. Phys. Status Solidi 208, 2765-2771. 

Suetaka, W. (1977) Infrared spectroscopy of investigating metal surfaces. Bunkou Kenkyu, J. Spectrosc. Soc. Jpn., 26, 251-265. This is a review written in Japanese Suetaka never published his thought on Equation (10.1) in English. Umemura, J. (2002) Reflection-absorption spectroscopy of thin films on metal substrates, In Handbook of Vibrational Spectroscopy, Vol. 2 (eds J.M. Chalmers and RR. Griffiths), John Wiley Sons, Ltd, Chichester, pp. 982-998. 

G. Grecz5mski, T. Kugler, M. KeU, W. Osikowicz, M. Fahlman, and W. R. Salaneck. 2001. Photoelectron spectroscopy of thin films of PEEXDT-PSS conjugated polymer blend A mini-review and some new results. / Electr Spectr Rel Phenom 121(1-3) 1-17. 

M. A. Vorotyntsev, J.-P. Badiali, G. Inzelt, Electrochemical impedance spectroscopy of thin films with two mobile charge carriers effects of the interfacial charging, J. Electroanal. Chem., 1999,472, pp. 7-19. 

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). 

Infrared (IR) spectroscopy and elUpsometry are used to measure the thickness of thin films with angstrom resolution. Ellipsometry has proven to be very useful in studies of dy-... 

Moreover, novel techniques of thin-film analysis (EXAFS, RBS, XPS, etc.) and improved sensitivity of traditional techniques (e.g., IR spectroscopy) have afforded a better understanding of anodic oxide growth and have even led to a reconsideration of commonly accepted concepts. 

The objective of the present work was to determine the influence of the light intensity on the polymerization kinetics and on the temperature profile of acrylate and vinyl ether monomers exposed to UV radiation as thin films, as well as the effect of the sample initial temperature on the polymerization rate and final degree of cure. For this purpose, a new method has been developed, based on real-time infrared (RTIR) spectroscopy 14, which permits to monitor in-situ the temperature of thin films undergoing high-speed photopolymerization, without introducing any additive in the UV-curable formulation 15. This technique proved particularly well suited to addressing the issue of thermal runaway which was recently considered to occur in laser-induced polymerization of divinyl ethers 13>16. 

To evaluate the reactivity of model compounds III-VIII in photoinitiated cationic polymerization, we have employed real-time infrared spectroscopy (RTIR). Thin film samples of the model compounds containing 0.5 mol% of (4-n-octyloxyphenyl)phenyliodonium SbF - as a photoinitiator were irradiated in a FTIR spectrometer at a UV intensity of 20 mW/cm2. During irradiation, the decrease in the absorbance of the epoxy ether band at 860 cm-1 was monitored. 

When the surfaces are highly reflecting as in the case of metals, external reflection spectroscopy (ERS) can be used with good success133). For optimum intensity of the reflection bands of thin films, angles of incidence near 88 are desirable. However, in order not to interfere with the incoming beam, angles of incidence near 80° are used. 

Many investigations of the molecular structure of thin films formed by y-APS deposited onto inorganic substrates from aqueous solutions have been carried out. Ondrus and Boerio [2] used reflection-absorption infrared spectroscopy (RAIR) to determine the structure of y-APS films deposited on iron, 1100 aluminum, 2024 aluminum, and copper substrates from aqueous solutions at pH 10.4. They found that the as-formed films absorbed carbon dioxide and water vapor to form amine bicarbonate salts which were characterized by absorption bands near 1330, 1470, 1570, and 1640 cm-1. y-APS films had to be heated to temperatures above about 90°C in order to dissociate the bicarbonates, presumably to free amine, carbon dioxide, and water. Since the amine bicarbonates failed to react with epoxies, the strength of adhesive joints prepared... 

The primary techniques used in this study include X-ray photoelectron spectroscopy (XPS), reflection-absorption infrared spectroscopy (RAIR), and attenuated total reflectance infrared spectroscopy (ATR). XPS is the most surface-sensitive technique of the three. It provides quantitative information about the elemental composition of near-surface regions (< ca. 50 A sampling depth), but gives the least specific information about chemical structure. RAIR is restricted to the study of thin films on reflective substrates and is ideal for film thicknesses of the order of a few tens of angstroms. As a vibrational spectroscopy, it provides the type of structure-specific information that is difficult to obtain from XPS. The... 

However, IR spectroscopy has not been widely used for hydrate studies. This is largely due to the technical problems associated with sample preparation (e.g., vapor deposition of thin films) to avoid the high IR absorptivity of water, and the difficulties of performing in situ and high pressure measurements. Therefore, this technique will not be further discussed here. 

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