Application of low‐energy noble‐gas ion scattering to the quantitative surface compositional analysis of binary alloys and metal oxides

Abstract

Low‐energy noble‐gas ion scattering (LEIS) probes the outermost atomic layer of a material, but a quantitative compositional analysis of this layer is not straightforward. It is demonstrated that quantification by calibration can be done, assuming that ion fractions and shielding effects are the same for the reference sample and sample of interest. These assumptions are critically evaluated and LEIS experiments on binary alloys and metal oxides are presented that can partly verify these assumptions. The LEIS measurements of a Cu–Au alloy and CuO powder as a function of initial energy indicate the absence of matrix effects in the ion fractions after scattering from the metal atoms in these systems. In metal oxides, shielding of surface metal atoms by shadowing/blocking and ion neutralization by neighbouring atoms can significantly influence the quantification of the metal atom concentration and is determined by the local atomic arrangement as illustrated by LEIS experiments of CuO and ZnO samples. © 1998 John Wiley & Sons, Ltd.

Determination of 16O and 18O sensitivity factors and charge-exchange processes in low-energy ion scattering

“…4, and used to determine the 18 O and 16 O sensitivity factors (g i ). 13 These values can be used as a reference to perform quantitative analysis on other 18 O-exchanged materials, provided that there are no matrix effects. Previous investigations of 3 He þ scattering by polydimethylsiloxane (PDMS) at energies from 800 eV to 5 keV showed a change in V c for O atoms in the E range of 800-1800 eV indicating a change in the dominant neutralization mechanism, 22 in agreement with the present work.…”

“…9,11,12 Since several processes may occur during the scattering event, a quantitative prediction of the neutralization behaviour (e.g., P þ dependence on the primary ion energy) is required for the selection of the optimal experimental parameters to perform a reliable quantitative LEIS analysis while avoiding timeconsuming calibrations. 6,13,14 In this work, we used the characteristic velocity method in order to study the neutralization behaviour of 4 He þ scattered from 16 O and 18 O and to determine the elemental sensitivity factors. A silica sample has been chosen as a reference material since the preferential sputtering can be neglected at the low ion doses used for the analysis.…”

How important is the (001) plane of M1 for selective oxidation of propane to acrylic acid?

“…These surface densities have been estimated as (ρ • N Av / M) 2/3 , where ρ is the bulk density, N Av is Avogadro's number and M the molar mass. It has been shown before [22] …”

Growth and thermal oxidation of Ru and ZrO2 thin films as oxidation protective layers

“…where ni is the stoichiometric number of the element i in the compound (ni=1 for a single element), M is the molar mass of the compound (or element), and NAV is Avogadro's number. 341 The We assume a certain value for the N or O reference peak area and then we use this initial value to calculate all surface coverages for Ru grown either on SiN or on SiO2. Then, this value is recursively changed till the Vegard's condition is valid for all deposited thicknesses.…”

“…341 Mass density values of 5.1±0.3, 5.7±0.3 and 2.3±0.3 g·cm -3 are determined from the respective fits to the XRR data of 10 nm-thick high-O ZrO2, low-O ZrO2 and aSi deposited samples, following the method described in Sec. 6 Fig.…”