Surface composition analysis

Surface composition analysis by LEIS is based on the use of noble gas ions as projectiles, making use of the superb surface sensitivity of LEIS under these conditions. A consequence of this surface sensitivity is that the LEIS energy spectrum consists of lines, one per element, if the masses differ sufficiently. The lines are narrow, because inelastic energy losses play a minor role here. Thus, the information on the atomic species present is deduced from the energy of the back-scattered ions, which can be converted to the mass of the scattering center. (Eig. 3.55 [3.141]). In Eig. 3.55 it is shown that the mass range, where LEIS is sensitive, depends on the projectile mass. 

A further example where quantitative surface composition analysis is possible for a non-trivial surface is shown in Fig. 3.58, where for the systems Ta -i- O and Nb -i- O adsorption the ion signal from the metal is shown as a function of the ion signal from O. In this binary example Eq. (3.43) are valid for the concentration ... 

The most common ions observed as a result of electron-stimulated desorption are atomic (e. g., H, 0, E ), but molecular ions such as OH", CO", H20, and 02" can also be found in significant quantities after adsorption of H2O, CO, CO2, etc. Substrate metallic ions have never been observed, which means that ESD is not applicable to surface compositional analysis of solid materials. The most important application of ESD in the angularly resolved form ESDIAD is in determining the structure and mode of adsorption of adsorbed species. This is because the ejection of positive ions in ESD is not isotropic. Instead the ions are desorbed along specific directions only, characterized by the orientation of the molecular bonds that are broken by electron excitation. 

Brongersma HH, Draxler M, de Ridder M, Bauer P. 2007. Surface composition analysis by low-energy ion scattering. Surf Sci Rep 62 63-109. 

Two-phase particles ranging from 10 to 20 microns in size, supported on a graphite substrate, were observed in-situ in the UHV chamber of a scanning Auger microprobe. Both surface composition analysis and imaging of the particles could be undertaken. The preparation of the samples has been described in detail elsewhere. ... 

A quantitative surface compositional analysis requires the comparison of the experimental yield of the individual clusters with corresponding yields obtained theoretically this may be done by numerical simulation of the complex collision process but the accuracy of the result cannot yet be ascertained. The accuracy of the compositional analysis depends to some extent on such poorly known factors as the interatomic potential, ionization cross-sections and quantum-mechanical corrections to a treatment based on classical trajectories. 

Applicability of Surface Compositional Analysis Techniques for the Study of the Kinetics of Hydride Formation... 

In this symposium emphasis is placed on the first class of methods. Isolated examples of the third class are discussed. Consideration of the second class is omitted entirely. Indeed, the scope of the symposium is perhaps best described as encompassing the more widespread techniques of surface compositional analysis as applied to materials science and electrochemistry oriented problems. Many modern surface analysis methods, e.g., those embodying tip sample geometries (21 22, 3, 34), those based on synchrotron radiation (23, 25), and those dealing with surface structure (15-20) and dynamics ( 3, 21-23), as opposed to surface composition, are not represented in the symposium program even though many of them enjoy "industrial applications" in the areas of electronics, metallurgy and catalytic chemistry. 

SURFACE COMPOSITIONAL ANALYSIS. AUGER ELECTRON SPECTROSCOPY (AES)... 

Ions have greater masses than electrons thus their transfer of energy to surface species is much more efficient. Ions incident on surfaces can break chemical bonds and eject atoms, molecules, or molecular clusters. Most of these species are neutral, but the ion impact may also ionize a fraction of these ejected particles. The detection of these ions, called secondary-ion mass spectroscopy (SIMS), is an important technique of surface-composition analysis. Ion bombardment is used frequently to remove unwanted molecular or atomic layers of impurities in order to clean a surface efficiently. Ion sputtering is also used to deposit thin films of the bombarded material... 

A.W. Czandema. Overview of Ion Spectroscopies for Surface Compositional Analysis. In A.W. Czandema and D.M. Hercules, editors, Ion Spectroscopies for Surface Analysis. Methods of Surface Characterization, Volume 2. Plenum Press, New York, 1991. 

Surface composition analysis by neutral and ion impact radiation SCANIIR spins fields 8... 

N. Sellin, J.S.C. Campos, Surface composition analysis of PP films treated by corona discharge. Mater. Res. 6, 163-166 (2003)... 

Because of its sensitivity to the top layer of the surface, ISS has proven very useful in providing surface compositional analysis of materials such as catalysts and alloys. ISS can also provide structural information on metal, semiconductor, metal o.vidc, and adsorbate surfaces. The major limitations of ISS are associated with difficulties in providing quantitative results, because of neutralization reactions and other interactions. Collisional processes and inelastic energy losses also make absolute mass determinations difficult. In compositional analysis, ISS is complementary to AES although not as generally applicable. 

Surface compositional analysis may be thought of as a cascade of processes in which the data interpretation is taken to increasing degrees of complexity, depending on the level of detail required to solve the particular problem under consideration. At the initial level, it may simply be sufficient to identify which elements are present near the surface of the specimen under examination. This... 

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