Photoelectron Spectroscopy XPS or ESCA

X-ray photoelectron spectroscopy (XPS), or given its other name Electron Spectroscopy for Chemical Analysis (ESCA), uses X-rays to excite photoelectrons. The emitted electron signal is plotted as a spectrum of binding energies. The photon is absorbed by an atom, molecule or solid leading to ionization and the emission of a core electron. Analysis will reveal the composition from a depth of 2 20 atomic layers and the electronic state of the surface region of the sample. XPS has the ability to identify different chemical states resulting from compound formation, which are revealed by the photoelectron peak positions and shapes. 

The quantification of the fiber surface concentration and distribution of acid groups and chemisorptive sites as a function of oxidative treatment level were determined by Denison et al [60] using a Ba labeling and XPS technique. 

Source Reprinted with permission from Gibbs HH, Wendt RC, Wilson FC, Carbon fibre structure and stability studies, Polym Eng Sci, 19(5), 342-349,1979. Copyright 1979, The Society of Plastic Engineers. 

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Table 8 shows results obtained from the application of various bulk and surface analysis methods to lithium metal at rest or after cyclization experiments, as well as at inert and carbon electrodes after cathodic polarization. The analytical methods include elemental analysis, X-ray photoelectron spectroscopy (XPS or ESCA), energy-dispersive analysis of X-rays (X-ray mi-... 

Surface composition and morphology of copolymeric systems and blends are usually studied by contact angle (wettability) and surface tension measurements and more recently by x-ray photoelectron spectroscopy (XPS or ESCA). Other techniques that are also used include surface sensitive FT-IR (e.g., Attenuated Total Reflectance, ATR, and Diffuse Reflectance, DR) and EDAX. Due to the nature of each of these techniques, they provide information on varying surface thicknesses, ranging from 5 to 50 A (contact angle and ESCA) to 20,000-30,000 A (ATR-IR and EDAX). Therefore, they can be used together to complement each other in studying the depth profiles of polymer surfaces. 

Photoelectron spectroscopy involves detection and analysis of the photoelectrons produced by interaction of radiation with a solid. This radiation may be X-rays (for X-ray photoelectron spectroscopy, XPS or ESCA) or ultraviolet radiation (UPS) it causes the removal of a single core or valence electron, respectively. The kinetic energy, Ek, of these electrons is given by the following equation ... 

They studied the chemistry of oxidized Si(lll) surfaces treated at two concentrations of the silane in trichloroethylene solution using angle-dependent X-ray photoelectron spectroscopy (XPS or ESCA). Although these are non-aqueous adsorption studies, sufficient surface silanol or adsorbed water is present for complete hydrolysis to occur because no trace of chlorine is seen in the XPS spectra. The two concentrations studied were 1% v/v, termed saturated, and <1/400% v/v, termed dilute. They lead to two distinct types of molecular bonding to the surface. C( 1 s) XPS spectra of these two situations are shown in Fig. 3. 

Polymer Surface Analysis. The major technique used for the surface analysis of polymers has been X-ray photoelectron spectroscopy (XPS or ESCA). However, this technique is often not adequate to determine the molecular structure of polymers. This has prompted many workers to explore the potential of SIMS for this work (11-16). Significant problems encountered with ion beam bombardment in conjunction with electron beam charge neutralization have been drift in the polymer surface potential and thermal damage from the combined effects of the electron and ion beams. These problems do not exist when utilizing FAB in conjunction with photoelectron charge neutralization. 

Castle (LI, 12) and McIntyre (5) have shown how X-ray photoelectron spectroscopy (XPS or ESCA) can be applied to corrosion problems and uses of Auger electron spectroscopy (AES) in corrosion have been given by Clough (18, 19) and Thomas et al ( 0). Possible uses of ion beams in corrosion studies were presented by Deamaley (JU). Raman spectroscopy (.22, 23) and ellipsometry (19) are not discussed in detail in this paper, but they offer the advantage of allowing in situ measurements in a wide variety of corrosive environments. 

Microanalytical methods are used to move further down in the characterization scale. X-ray photoelectron spectroscopy (XPS or ESCA), (see Barr) Auger electron spectroscopy (AES), and secondary ion mass spectroscopy (SIMS) as presented by Leta for imaging FCC catalysts, are surface analysis techniques providing chemical analy-... 

In the present paper we describe a detailed systematic investigation of these materials for an extended range of cathode materials, including silicon, germanium, molybdenum, tungsten and copper. The injected monomer is perfluoropropane and the polymers are analyzed by means of X-ray photoelectron spectroscopy (XPS or ESCA), while the low molecular weight neutral products in the plasma effluent are monitored by means of mass spectrometrlc techniques. 

In an extensive series of publications. X-ray photoelectron spectroscopy (XPS or ESCA) has been demonstrated to be an extremely powerful tool for the Investigation of structure, bonding and reactivity In polymeric systems ( )- Its small sample requirement, non destructive nature and ability to study solid samples In their working environment with a minimum of preparation, have made It particularly amenable to the study of crossllnked materials whose Insolubility make them difficult to study by any other technique (7). Indeed a perusal of the literature readily affirms that In the field of plasma polymerization ESCA has played an Important role In recent... 

X-ray photoelectron spectroscopy (XPS, or ESCA) measures the energy of the inner shell electrons ejected when the surface is irradiated with an X-ray beam in ultra-high... 

It became common in the early development of X-ray photoelectron spectroscopy (XPS or ESCA) for users to classify some of the shifts detected for elemental covalent bonding energy peaks following changes in the chemistry of that element as a chemical shift. This section will describe how Eb can be affected and how measurement of Eb can be used to analyze the materials chemistry. Using current nomenclature and/or arguments, the problem of accurately measuring... 

Surface analysis refers to the characterization of the outermost layers of materials. A series of techniques have been undergoing continuous development since the late 1960s based on ultra-high vacuum (UHV) technology. The most useful of these methods provide information on surface chemical composition and four techniques satisfy this requirement X-ray photoelectron spectroscopy (XPS or ESCA), Auger electron spectroscopy... 

In this chapter we will discuss spectroscopic methods that involve inner electrons [5.1, 5.2]. Such electrons are much more strongly bound than outer electrons and the interaction energies become correspondingly high. Two kinds of methods are used to study inner electrons, those that are based on absorbed or emitted X-ray radiation (X-ray spectroscopy) aaid those dealing with energy measurements on emitted photoelectrons photoelectron spectroscopy (XPS or ESCA)). 

There are numerous experimental techniques that can be employed in the characterization of structure of PES [34-38]. A systematic study was conducted to investigate the changes of PES using nuclear magnetic resonance (13C NMR), Fourier transform infiared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS or ESCA) [9,39]. 

The treated substrates were composed of a porous, 5 m-thick, alumina layer elaborated onto an alumina plate of 0.3 mm. These plates, provided by AGFA-Gevaert, were protected with a gum layer. Before using the plate, this layer was removed with rinseage with distilled water and dried by compressed air. In order to characterize the treated plates, two main techniques were used contact angles measurements and X-ray photoelectron spectroscopy (XPS or ESCA). 

X-Ray photoelectron spectroscopy (XPS) or ESCA is another routine analytical technique whose application to CPs is best illustrated by examples. Wide-spectrum XPS is a simple tool for elemental analysis, useful, e.g., to see the presence of an atom belonging to a particular dopant to verify doping. Higher resolution (core-level) XPS is typically useful for determining oxidation states of a central heteroatom, e.g. the N-atom in poly(aromatic amines), hence elucidating the redox state of the polymer or at least of the central heteroatom. Finally, valence-level spectra, at very low energies, have been said to be usable for estimation of density of states, although their accuracy is questionable. 

X-ray photoelectron spectroscopy (XPS or ESCA) analyses were carried out on a PHI-TFA XPS spectrometer (Physical Electronics Inc). The analyzed area was 0.4 mm in diameter and about 3-5 nm in depth. This high surface sensitivity is a general characteristic of the XPS method. Sample surfaces were excited by X-ray radiation from a monochromatic Al source at a photon energy of 1486.6 eV. C Is, F Is, 0 Is, N Is and Si 2p spectra were acquired with an energy resolution of about 1.0 eV with an analyzer pass energy of 58 eV. Quantification of surface composition was performed from XPS peak intensities measured on three different spots of the sample, taking into account the relative sensitivity factors provided by the instrument manufacturer (Moulder, 1995). 

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