Quantitative Auger and XPS Analysis of Thin Films

Auger Electron Spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) have many aspects in common. Therefore, tests of aspects for one spectroscopy, applicable to the other, should be validated for both. Digital databases of elemental spectra for both AES and XPS have thus been measured using an electron spectrometer that has been fully calibrated for its intensity and energy axes. These databases of true spectra give absolute Auger electron yields and relative photoelectron yields. The AES data are measured for both 5 and 10 keV electron beam energies, whereas the XPS data are measured for both Al and Mg unmonochromated x rays at the magic angle. In addition to these we have measured reflected electron energy loss spectroscopy (REELS) data to provide a third database. The combination of these databases allows a refinement of the theories to obtain an overall convergence between theory and experiment. Improvements to the theory have been obtained by identifying three classes of parameter, those (i) for both AES and XPS, such as electron transport, the methodology of evaluation of peak areas, and the spectrometer response function, (ii) for AES only, such as the electron ionization cross section, backscattering, and specific electron backgrounds, and (iii) for XPS only, such as the photon-ionization cross section. Additionally, the use of REELS data for background subtraction seems significantly better than the use of any one single Tougaard universal cross section in the determination of the AES and XPS intensities in the databases. The formalism for quantitative analysis in AES and XPS, using relative sensitivity factors, has been revised to develop an accurate matrix-less formalism that is very simple for use by the analyst. This formalism, involving “average matrix sensitivity factors” rather than “pure element sensitivity factors,” has the same accuracy as the matrix formalism but its simplicity permits ready extension to systems beyond binary.

Various commercially available surface treatments are being explored for use on stainless steel components in mass spectrometer inlet systems. Type A-286 stainless steel coupons, approximately 12.5 mm in diameter and 3 mm thick, were passivated with one of five different surface treatments; an untreated coupon served as a control. The surface and near-surface microstructure and chemistry of the coupons were investigated using sputter depth profiling using Auger electron spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy (SEM). All the surface treatments studied appeared to change the surface morphology dramatically, as evidenced by lack of tool marks on the treated samples in SEM images. In terms of the passivation treatment, Vendors A-D appeared to have oxide layers that were very similar in thickness to each other (0.7–0.9 nm thick), as well as to the untreated samples (the untreated sample oxide layers appeared to be somewhat larger). Vendor E’s silicon coating appears to be on the order of 200 nm thick.

X-ray photoelectron spectroscopy (XPS) and x-ray-induced Auger electron spectroscopy (XAES) were used to analyze two lots of untreated LiNi0.5Co0.2Mn0.3O2 powder and one of the two lots of LiNi0.5Co0.2Mn0.3O2 powder recalcined in air at 750 °C obtained from TODA America. X-ray photoelectron and x-ray-induced Auger electron spectra were obtained using incident monochromatic Al Kα radiation at 0.834 01 nm. A survey spectrum together with Ni 2p, Co 2p, Mn 2p, Ni LMM, O 1s, C 1s, Ni 3s, Co 3s, Mn 3s, Ni 3p, Co 3p, Li 1s, and Mn 3p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals and show only minor sulfur contamination. Making use of the O 1s, Ni 3p, Co 3p, Mn 3p, and Li 1s lines and neglecting the components related to surface contaminants, XPS quantitative analysis reveals an altered stoichiometry of the air-exposed powder surfaces for the first lot, the first lot recalcined, and the second lot of LiNi0.3Co0.1Mn0.2O1.2, LiNi0.4Co0.1Mn0.3O1.5, and LiNi0.4Co0.1Mn0.2O1.3, respectively.

Influence of sputtering on the surface composition of MoNi alloys

The important role of surface sensitive characterization techniques such as Auger electron spectroscopy (AES), X-ray photo electron spectroscopy (XPS), time of flight scanning ion mass spectrometry (TOF-SIMS) and High resolution transmission electron microscopy (HRTEM) for the characterization of different phosphor materials is discussed in this short review by giving selective examples from previous obtained results. AES is used to monitor surface reactions during electron bombardment and also to determine the elemental composition of the surfaces of the materials, while XPS and TOF-SIMS are used for determining the surface chemical composition and valence state of the dopants. The role of XPS to determine the presence of defects in the phosphor matrix is also stated with the different examples. The role of HRTEM in combination with Energy dispersive spectroscopy (EDS) for nanoparticle characterization is also pointed out.

Background removal in auger electron spectroscopy: a new experimental approach

We have developed a multifunctional surface analysis system based on a scanning electron beam for nanofabrication and characterization of surface reactions for fabrication processes. The system performs scanning electron microscopy (SEM), scanning reflection electron microscopy (SREM), Auger electron spectroscopy (AES), and x-ray photoelectron spectroscopy. Nanometer scale resolution is obtained for ultrahigh vacuum (UHV)-SEM while the mechanical pumping instruments are operated. Single atomic steps on Si(111) surfaces are observed through SREM. Surface sensitive AES measurement is achieved with SREM geometry; this has a great advantage for investigating atomic step related surface reactions. High spatial resolution AES analysis is also achieved by using a nanometer scale probe beam. Auger electron signals from a hundred Ag atoms on a Si(111) surface are successfully detected with high sensitivity.

X‐ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES) are two of the most powerful materials analysis techniques available today. First, the fundamental concepts underlying these methods are presented in simplified form. Then the most important problem areas of concern to workers in these fields are examined. These are: radiation damage, the technology of ion milling, and quantitative analysis. The complexity of these areas is illustrated from what is already known, and some problems that arise in areas that are still incompletely understood are discussed. Finally, the relative merits of XPS and AES are considered by evaluating the performance of each technique with respect to: (1) sensitivity, (2) speed, (3) spatial resolution, (4) depth resolution, (5) chemical bonding information, (6) sample damage, (7) quantitative analysis, and (8) electrostatic charging problems. Scores have been assigned for each of these 8 criteria for XPS and AES; at present, AES is found to have a significantly higher total score. These criteria have also been evaluated assuming that all the theoretical limits can be attained. In that limit, some problems are expected to remain for AES with respect to sensitivity, chemical bonding information, damage, and charging; however, with XPS, all of the performance criteria become superior to AES except for spatial resolution. The total performance score for XPS then becomes much higher than for AES.

10 - Surface Analysis Methods for Contaminant Identification

The interactions of cyclopentane with clean and bismuth-covered Pt(111)

Studies of liquid surfaces with electron spectroscopy are comparetively scarce even though the microscopic understanding of these systems could benefit to the same extent as is the case for surfaces of solids. The short mean free path λe of slow electrons in condensed matter ensures that electrons leaving the surface must originate from a site which is separated from the very surface by at most a few times λe. This holds for XPS(=x-ray photoelectron spectroscopy), UPS (=ultraviolet photoelectron spectroscopy), AES (=Auger electron spectroscopy) and EELS(=electron energy loss spectroscopy). Indeed, these techniques have been used by a small number of groups for the investigation of liquid surfaces. The first such study was published by H. and K. Siegbahn on formamide using XPS 1, followed by a large number of works by H. Siegbahn and coworkers on several liquid surfaces, e.g. solutions of surface active salts 2,3,4. Two groups have made use of the HeI resonance line to perform UPS on liquid surfaces 5,6. Ballard showed that AES and EELS (with energy losses in the eV range) could reproducibly be carried out on these systems 7 even though there remains the need to understand the precise contribution of these methods to the diagnosis of liquid surfaces. The above mentioned spectroscopies have in common that their surface sensitivity is governed by the value of the mean free path λe of the emitted electrons. There is, however, one electron spectroscopy that is distinguished in that its observation depth is not related to a mean free electron path. It is MIES (=Metastable Induced Electron Spectroscopy), a technique which monitors exclusively the topmost layer of a surface8. The energy needed for electron emission is supplied by the excitation energy (19.819 eV) of metastable helium atoms He *(1s2s,3S). The surface sensitivity of MIES goes so far that even the orientation of the molecules in the topmost layer can be determined 8.

Ionization energies of liquids from energy distribution, quantum yield and second derivative curves

Generation of acids from mine waste: Oxidative leaching of pyrrhotite in dilute H 2SO 4 solutions at pH 3.0

Some aspects of the adsorption of O2 on Ni have been studied using electron‐excited Auger electron spectroscopy (AES) and x‐ray photoelectron spectroscopy (XPS). Changes in the oxygen Auger line shape were observed with increasing oxygen exposure, together with a broadening and energy shift of the main oxygen Auger peak. Measurements were also made of the broadening and energy shifts of the Ni L3VV Auger peak on oxidation. The variation in oxygen Auger signal strength with oxygen exposure shows that two distinct adsorption stages occur. Relative AES and XPS signal strengths from clean and heavily oxidized Ni were measured and compared with the atomic densities of Ni in pure Ni and NiO. To accurately measure the changes in signal strengths, the AES and XPS data had to be integrated to remove the effects of line shape changes.

Cd 2+ uptake by calcite, solid-state diffusion, and the formation of solid-solution: Interface processes observed with near-surface sensitive techniques (XPS, LEED, and AES)