Surface analysis techniques using light

There are still other surface analysis techniques including ellipsometry, surface enhanced Raman scattering, light scattering, nano-hardness measurements etc. which are used for specific investigations. It is, however, already evident from this discussion that many new and powerful techniques now are available which offer the capability of investigating various aspects of polymer surfaces on a molecular level. Some of those techniques are surface specific while others can be used for the analysis of buried interfaces, too. 

Isotopic Studies. In this analysis mode the mass spectrometer Is used to determine the relative abundance of different Isotopes of the same element. SIMS Is the only common surface analysis technique that can distinguish the Isotopes of both the light and heavy elements. This mode Is advantageously used In mechanistic studies using Isotopically labelled samples. By using different Isotopes of the same element experiments can be performed without concern for the differences In chemical effects between the species. 

Various techniques can be used for the characterization of surface-modified nanoparticles (Muller, 1991). In the case of PEG-covered nanospheres, atomic force microscopy and freeze-fracture have been used to determine their morphology, light scattering has been employed to measure their size, and surface analysis techniques have been applied to detect the presence of PEG on the surface and the stability of this coating, etc. Some of these techniques are presented in this section. 

SIMS and SNMS are versatile analytical techniques for the compositional characterization of solid surfaces and interfaces in materials research.92-94 As one of the most important applications, both surface analytical techniques allow depth profile analysis (concentration profile as a function of the depth analyzed) to be performed in materials science and the semiconductor industry with excellent depth resolution in the low nm range. For depth profiling in materials science, dynamic SIMS and SNMS using high primary ion beam doses are applied. Both techniques permit the analysis of light elements such as H, , C and N, which are difficult to measure with other analytical techniques. 

The whole field received a new impetus after the first oil crisis, when Fujishima and Honda reported on the photoelectrolysis of water at Ti02-electrodes [13], Whereas, before the oil crisis, most basic models and results had been published only by 3-4 research groups in the world, many other scientists entered the field after this crisis and studied solar applications, and hundreds of papers were published. Since then, many processes at semiconductor electrodes have been studied more quantitatively by using not only standard electrochemical methods, but also new techniques, such as spectroscopic surface analysis (see e.g. [12]). Naturally, photoeffects played a dominant role in these investigations. These were not only restricted to reactions induced by light excitation within the semiconductor electrode [11], but were also extended to the excitation of adsorbed dye molecules [14,15]. 

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