Surface analysis techniques, study

The detection of impurities or surface layers (e.g., oxides) on thick specimens is a special situation. Although the X-ray production and absorption assumptions used for thin specimens apply, the X-ray spectra are complicated by the background and characteristic X rays generated in the thick specimen. Consequently, the absolute detection limits are not as good as those given above for thin specimens. However, the detection limits compare very favorably with other surface analysis techniques, and the results can be quantified easily. To date there has not been any systematic study of the detection limits for elements on surfaces however, representative studies have shown that detectable surface concentrations for carbon and... 

Application of Surface Analysis Techniques in the Study of Catalyst Systems... 

IR, etc. The chemical and physical changes within 3nm of the surface of the pellet or fluidized bead can be studied by surface analysis techniques such as AES, XPS, ISS, SIMS, RBS, etc. 

UHV techniques are usually classified in terms of the electron/photon method, as is shown in Table 2.3 which lists the common electron bombardment and emission techniques that have been employed in electrochemical studies. A detailed description of UHV surface analysis techniques is beyond the scope of this book there are many excellent reference texts that can be consulted for this purpose (see further reading list). It is sufficient to note that methods involving electron bombardment or emission are inherently surface-sensitive as a result of the low pathlength, or escape depth, of electrons in condensed media. In addition, Table 2.3 briefly describes the type of information each method provides. 

There is a wealth of information available on CO chemisorption over single-crystal and polycrystalline platinum surfaces under ultrahigh-vacuum conditions research efforts in this area have gained a significant momentum with the advent of various surface analysis techniques (e.g., 2-8). In contrast, CO chemisorption on supported platinum catalysts (e.g., 9, 10, 11) is less well understood, due primarily to the inapplicability of most surface-sensitive techniques and to the difficulties involved in characterizing supported metal surfaces. In particular, the effects of transport resistances on the rates of adsorption and desorption over supported catalysts have rarely been studied. 

Recently, the steady-state reaction kinetics of CO oxidation at high pressure over Ru , Rh " , Pt, Pd, and Ir single crystals have been studied in our laboratory. These studies have convincingly demonstrated the applicability and advantages of model single crystal studies, which combine UHV surface analysis techniques with high pressure kinetic measurements, in the elucidation of reaction mechanisms over supported catalysts. 

The way in which fluoride is taken up by glass-ionomers has been studied using surface analysis techniques. Dynamic secondary ion mass spectroscopy (SIMS) shows that most of the fluoride becomes concentrated in the surface [248]. Its concentration with depth varies as an error function relationship [248]. X-ray photoelectron spectroscopy (XPS) has suggested that fluoride taken up becomes associated with calcium [249]. However, the form of this association is unclear, because calcium fluoride as such is very insoluble, and when added to a fluoride-free glass-ionomer cement, caused no fluoride to be released [234]. It therefore seems unlikely that the calcium-fluoride association results in formation of Cap2, and further research is necessary to determine the precise nature of the calcium-fluoride association, and thus to resolve this paradox. 

Complementary data was obtained by other surface analysis techniques. In one study sputter profiling of Ga, As and 0 by AES and XPS showed a deficiency of As in plasma grown oxides... 

In the chemical reprocessing of spent reactor fuel, there are a number of possible applications of surface analysis techniques. Quite recent, XPS studies of dissolution mechanisms of UO2 fuel have begun. Studies in support of surface protection of dis-... 

The case study. The composition of the surface tribofilms formed by ZDDP and of carbonate-phenate RMs in a cam and tappet friction apparatus were examined using a combination of surface analysis techniques. Adding carbonate-phenate RMs to ZDDP resulted in partial replacement of zinc by the detergent metal and loss of the higher molecular weight phosphates in favor of ortho- and... 

Many surface analysis techniques have been applied in studies on the reaction mechanism of APTS with silica gel.15 In order to study the chemical structure and interactions of the surface compound, FTIR has been recognized as a very powerful tool.2 8-16-17 18... 

A very useful source of complementary information is XPS (X - ray Photo - electron Spectroscopy), which is a typical surface analysis technique. XPS is often used as a valuable tool in studies of the interaction of silanes with silica40,41,42,43 or neoceramic coatings.44,45 The basic principles of the XPS technique are described in appendix B. 

XPS and other surface analysis techniques to the study of electroactive polymers and their molecular modifications are pointed out We assume that the readers are familiar with the historical development of electroactive polymers since the pioneering work on (CH)X [4, 5],... 

A surface analysis technique that has the potential to detect structural chemical changes in polymer surfaces, including low-molecular weight material formation, is static SIMS. Its capabilities for characterizing polymers by virtue of their fingerprint spectrum nave been amply demonstrated in recent years (5 6). The technique is more surface sensitive than XPS and can detect structural differences, even in hydrocarbons (7). It is, therefore, highly complementary to XPS. Nevertheless, only very few applications to the study of modified polymer surfaces have been published. Among these are reports on SIMS analysis of flame-treated polypropylene and plasma-fluorinated polyolefin surfaces (8 9). 

Cohalt Silicides. The interest in the study of metal silicides is growing at much faster rate because of their use as interconnects and contacts in semiconductor and VLSI technology. The silicides in general have lower resistivity than polysilicon and are able to withstand high annealing temperatures than most pure metal interconnects. In the development of the metal-silicide studies the most important quantities of interest are metal/Si ratio as a function of depth, the silicide film thickness and the identification and the quantification of any contaminants present. The conventional surface analysis techniques... 

Ceria Surfaces and Films for Model Catalytic Studies Using Surface Analysis Techniques ... 

CERIA SURFACES AND FILMS FOR MODEL CATALYTIC STUDIES USING SURFACE ANALYSIS TECHNIQUES... 

Among the various surface analysis techniques which are currently available to catalysis chemists. X-ray photoelectron spectroscopy is certainly the one having found the widest application in the study of zeolitic materials. Reflecting this significance, this text will mostly dwell upon XPS and its relevance to zeolites, with some mentions of the contributions of such other techniques as Auger Electron Spectroscopy (AES), Ion Scattering Spectroscopy (ISS) and Secondary Ion Mass Spectrometry (SIMS). 

In Sect. 1.2.1 of the present chapter, we describe the most important cluster sources successfully used today. Section 1.2.2 introduces experimental techniques for mass-selecting single cluster sizes from the distribution generated by the cluster sources. In the gas phase as well as for clusters on surfaces, the densities are extremely low, thus only highly sensitive methods can be used for the characterization of the chemical and catalytic properties of the model systems. Some of the most commonly used techniques employed in gas-phase experiments are presented and discussed in Sect. 1.2.3, surface analysis techniques for cluster studies are presented in Sect. 1.2.4. 

The relatively slow rate of hydrocarbon fuel cell oxidations prompted an intensive examination of the adsorption characteristics of organic reactants in the 1960s. Because of the low potential for the development of hydrocarbon fuel cells, such studies have largely subsided today and no modern surface analysis techniques have been applied to characterize intermediates. Conventional adsorption studies of carbonaceous species have been reviewed repeatedly (7, 9-12, 100 -, therefore, we summarize here only some essential adsorption features for fuel cell and selective electrocatalytic oxidations. 

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