Auger electron spectroscopy depth-composition profiles

AES Auger electron spectroscopy After the ejection of an electron by absorption of a photon, an atom stays behind as an unstable Ion, which relaxes by filling the hole with an electron from a higher shell. The energy released by this transition Is taken up by another electron, the Auger electron, which leaves the sample with an element-specific kinetic energy. Surface composition, depth profiles... 

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. 

The elemental composition, oxidation state, and coordination environment of species on surfaces can be determined by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) techniques. Both techniques have a penetration depth of 5-20 atomic layers. Especially XPS is commonly used in characterization of electrocatalysts. One common example is the identification and quantification of surface functional groups such as nitrogen species found on carbon-based catalysts.26-29 Secondary Ion Mass spectrometry (SIMS) and Ion Scattering Spectroscopy are alternatives which are more surface sensitive. They can provide information about the surface composition as well as the chemical bonding information from molecular clusters and have been used in characterization of cathode electrodes.30,31 They can also be used for depth profiling purposes. The quantification of the information, however, is rather difficult.32... 

Auger electron spectroscopy (AES) is particularly suited for surface analysis (depth 0.5-1 nm). AES depth profile analysis was employed to determine the thickness and composition of surface reaction layers formed under test conditions in the Reichert wear apparatus in the presence of four different ZDDPs additives at different applied loads (Schumacher et al., 1980). Using elemental sensitivity factors the concentration of the four elements (S, P, O, C) was determined at three locations corresponding to a depth of 1.8, 4.3, and 17 nm. No significant correlation between wear behavior and carbon or oxygen content of the reaction layer was observed. A steady state sulfur concentration is reached after a very short friction path. Contrary to the behavior of sulfur, phosphorus concentration in the presence of ZDDPs increases steadily with friction path, and no plateau value is reached. 

The surface of the particles can be studied directly by the use of electron microprobe X-ray emission spectrometry (EMP), electron spectroscopy for chemical analysis (ESCA), Auger electron spectroscopy (AES), and secondary ion-mass spectrometry. Depth-profile analysis determines the variation of chemical composition below the original surface. 

The composition of wet thermal oxide on SiC has been established to be close to stoichiometric Si02 from Auger electron spectroscopy sputter depth profiles and from the refractive index of the oxide determined by ellipsometry [4,12,14,19,21,24-27]. Dry oxide on 3C-SiC has been found to contain much more silicon than stoichiometric Si02 [27]. The carbon content of the SiC thermal oxide layer, away from the interface, determined by Auger spectroscopy, has been reported as at below detection limits for wet oxide on 6H-SiC [25] at below detection limits [24,26] and also at 2% for dry oxide on 3C-SiC [27] and at 14% for wet oxide on 3C-SiC [27]. The oxide on SiC grown below 1200°C is amorphous, but above 1200°C the oxide grown is increasingly crystalline [15,18,20,22-24,28]. 

P.M. Hall and J.M. Morabito. Compositional Depth Profiling by Auger Electron Spectroscopy. In R. Vanselow, editor. Chemistry and Physics of Solid Surfaces, Volume 2. CRC Press, Boca Raton, FL, 1979. 

Typical procedures for chromic and phosphoric acid anodizing are given in Pretreatment of aluminium, and the durability (see Durability - fundamentals) of bonds to the surfaces formed is discussed. An example of a profile of elemental composition in depth for a phosphoric acid anodized film is shown in Auger electron spectroscopy. 

Besides the chemical and radiochemical composition, other properties of the collected materials are also often of interest, such as the natine of the chemical compounds present in these substances. For example, the structure of oxide compounds after isolation from the base material or from the coolant is analyzed by X-ray diffractometry or by Mdssbauer spectrometry. Other microanalytical techniques can be directly applied to oxide layers deposited on surfaces, e. g. of steam generator tube sections. Examples in this field are Auger electron spectroscopy for the determination of element concentrations in micrometer areas and X-ray induced photoelectron spectroscopy for the determination of the chemical states of the individual elements. In order to obtain depth profiles over the thickness of the oxide layer, these techniques often are combined with an argon sputtering process (e. g. Schuster et al., 1988), which removes nanometer fractions from the swface prior to the next analysis step. By y spectrometry of the specimen after each sputtering step, the profile of the radionuclides in the oxide layer can also be determined. 

Depth profiling (characterization) The determination of elemental composition as a function of distance from the surface. The analysis may be destructive (Example sputter profiling using auger electron spectroscopy (AES)) or non-destructive (Example profiling using Rutherford backscattering spectrometry (RBS)). 

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