Auger Electron Spectroscopy Data Research Articles

Incorporation of oxygen chemisorbed on Ru(001)

The behavior of oxygen on the basal plane of ruthenium has been studied at temperatures above 300 K using uptake measurements, thermal desorption spectroscopy (TDS) and Auger electron spectroscopy (AES). A temperature-independent initial sticking coefficient of 0.8 ± 0.1 is calculated from uptake measurements made at 320 K and 900 K, while AES data at 320 K gives a value of 0.62 ± 0.05. At 320 K the sticking coefficient declines with exposure more rapidly than at 900 K. Moreover, at 320 K the total oxygen uptake at saturation is less than at 900 K. TDS measurements after saturation exposure show a single high temperature O 2 desorption peak (≈ 1350 K) which is larger when the exposure temperature is 900 K than when it is 320 K. In either case, the amount of O 2 desorbed is significantly less than the amount adsorbed. A consideration of processes, other than O 2 desorption, which can reduce the surface oxygen concentration indicates that penetration into the first few layers beneath the surface makes the most significant contribution. Incorporation of oxygen into the subsurface region, upon heating a surface saturated at 320 K, occurs with a measurable rate at temperatures as low as 400 K. The distribution of oxygen in the first few atomic layers beneath the surface depends strongly on the thermal history of the sample. A model which is qualitatively consistent with the data involves the rapid removal of a large amount of the surface oxygen by incorporation mainly into the first subsurface layer followed by much slower uptake into the deeper layers.

The composition of organo-tin polymer films on metallic substrate materials

Glow discharge films with various ratios of carbon to tin were deposited on various metals and on glass. The ratio of carbon to tin was determined quantitatively by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The AES data correlated well with the XPS data. The X-ray beam and electron impact effects on organo-tin films influence the composition and are discussed in detail. The ratio of carbon to tin was not constant throughout the glow discharge reactor and this inhomogeneity is accounted for by the prevalence of “atomic” polymerization rather than “molecular” polymerization. We demonstrated that the substrate material had a definite influence on the composition of the films.

Auger electron spectroscopy of stoichiometric chromium carbides and carbide precipitates at grain boundaries of type 304 stainless steel

Auger electron spectroscopy (AES) data on carbide phases at the grain boundaries of type 304 SS are reported. The carbide phase was identified from the unique shape of the carbide peak in the AES spectrum and composition of the carbide was obtained from the Auger Spectra from stoichiometric chromium carbides, iron and nickel carbide and the pure graphite, iron, chromium, and nickel. (FS)

Auger and electron energy loss spectroscopy of oxygen chemisorption on tin

Studies of the room temperature chemisorption of O 2 on Sn surfaces using Auger electron spectroscopy (AES) and electron energy loss spectroscopy (EELS) are reported. AES and EELS spectra are presented for clean Sn, SnO, SnO 2 and Sn with exposure to O 2. Previously unreported fine structure in the MNN Auger spectrum of Sn are assigned to plasmon loss peaks or associated with multiplet structure of the final two-hole 4d 8 state. The MNN Auger lines in tin oxide are chemically shifted 5.5 eV down in energy with respect to those of Sn and contained no fine structure. The Auger spectrum of Sn with exposure to O 2 at 5 × 10 −6 Torr appears to be a composite of emission from clean Sn and tin oxide. Because the Auger spectra from SnO and SnO 2 were found to be nearly identical, the Auger data from Sn + O 2 could not be used to determine which oxide - SnO or SnO 2 - was present following chemisorption. This difficulty was overcome by comparing instead EELS data obtained from Sn + O 2 with EELS spectra characteristic of SnO and SnO 2. Analysis of the present EELS and AES data and consideration of available photoemission data on the Sn/O system lead to the following as being the most likely conclusion: under the conditions of O 2 chemisorption used in the present experiment, both SnO and SnO 2 are present at the surface with SnO being most probably located over the SnO 2. The present data also lend support to the possibility, suggested by earlier photoemission measurements, that a metal-rich surface is retained during these chemisorption experiments. The exact distribution of metallic Sn in the surface region remains an open question.

Surface structure and composition from electron stimulated desorption

By combining electron stimulated desorption (ESD) with low energy electron diffraction (LEED), Auger electron spectroscopy (AES) and work function change (Δφ) measurements the information content of ESD with regard to surface structure and composition is examined, using the surface systems O/W(100) and O/W(110). Although it is not possible to separate the local interaction from the ion escape phase, the comparison of the ESD results with Information derived from LEED, AES and Δφ and the use of simple models of the local interaction gives a rather detailed picture of the location and environment of adsorbed atoms which provides a reasonably reliable basis for the interpretation of UPS spectra of adsorption layers. ESD is extremely sensitive to adsorbed layers. The fact that the ion signal depends not only on coverage but also on the structure and structure-dependent properties of the adsorbate makes on the one hand coverage determination difficult if not impossible, on the other hand opens the door to structure analysis. The potential for obtaining structure information can be easily assessed by comparison with electron probe results. In comparison with other ion probes such as ion scattering spectroscopy and secondary ion mass spectroscopy, ESD is at present the most promising ion probe method for obtaining information on the location of adsorbed atoms from angular and energy distribution measurement (ESDIAD and ESDIED). This is clearly seen by the comparison with the structural data derived from LEED, AES and Δφ measurements for the complex system O/W(100). The consistency of the data obtained with ESD and electron probe techniques lends strong support to the simple models on which the analysis of the ESD results from chemisorbed layers are based. The comparison of ESD results from the system O/W(100) at high coverage and from O/W(110) with 0 + ion emission from oxides shows, however, that caution is in place when assigning ESD features to atoms chemisorbed on the metal surface. Without a careful analysis of the ion energy, threshold and/or cross-section such ions cannot be distinguished from ions produced by dissociation of oxides which may be present on the surface only in small quantity. These ions usually are not related to the chemisorbed species which covers most of the surface and therefore dominates the signals seen with (nearly) all other surface probes. If the consistency of LEED, AES, Δφ and ESD data for O/W(100) is not fortuitous, then ESD has already given some important feed-back to the electron probe techniques: the structural models derived from vibrational ELS spectra have to be revised. Increasing accumulation of experimental data and deepening of the theoretical understanding of the physical processes involved in ion emission will have to show how much further information complementary to that from electron probes can be obtained from ion probes.

Global methods in the inversion of a self-convolution

New algorithms to self-deconvolve such experimental spectra as those obtained in AES and APS are devised. The approach used is global and based upon the fast Fourier transform (FFT) algorithm and digital signal processing concepts. A description of the algorithms is given and comparison of performance is made for Auger electron spectroscopy (AES) data for graphite.

Electron induced luminescence as a technique for studying the adsorption of oxygen and the oxidation of thorium

The luminescence of thorium in an electron beam is affected by the interaction of oxygen with the metal surface. Luminescence intensity measurements, along with Auger electron spectroscopy data, suggest that both adsorbed molecular and atomic oxygen enhance the luminescence and that the luminescence intensity is especially sensitive to the amount of molecular oxygen adsorbed on the thorium surface. These findings are interpreted in terms of a dissociative mechanism of oxygen adsorption that leads to the formation of thorium oxide at the surface.

Grain boundary precipitation in 18Ni maraging steels

Recent scanning Auger electron spectroscopy data which reinforces the important role of TiC in the thermal embrittlement process were reviewed. These results show that impurity segregation is not a general phenomena in maraging steels and cannot therefore be considered to be the principal cause of the additional reductions in fracture toughness observed in aged thermally embrittled alloys.

Pt2Si and PtSi formation with high-purity Pt thin films

Formation rates of Pt2Si and PtSi have been measured using 1.8-MeV 4He+ backscattering spectroscopy. Both silicide layers were grown with t1/2 time dependence, but the formation of PtSi starts only after all available Pt has reacted for the formation of Pt2Si, in disagreement with previously reported results. The activation energies have the common value 1.5±0.1 eV. Auger electron spectroscopy data confirmed the deposited Pt film purity and show that the contaminants contained in the sputter-deposited Pt layer segregate at the Pt2Si/Pt interface. It is postulated that this interfacial impurity buildup can affect the formation rate of Pt2Si and the further evolution of the system.

Some aspects of an AES and XPS study of the adsorption of O2 on Ni

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.

929. Low-voltage triode sputtering and backsputtering with a confined plasma: IV. Heat transfer characteristics: B E Nevis and T C Tisone,J Vac Sci Technol, 11 (6), 1974, 1177–1185

Radiation-induced and precipitation-induced grain-boundary segregation profiles are routinely measured by scanning-transmission electron microscopy using energy-dispersive X-ray spectroscopy (STEM-EDS). However, radiation-induced grain-boundary segregation (RIS) profiles achieved at low and moderate temperatures are exceedingly narrow, typically less than 10 nm full width at half maximum. Since the instrumental spatial resolution can be a significant fraction of this value, the determination of grain boundary compositions poses a formidable challenge. STEM-EDS and Auger electron spectroscopy (AES) measurements are reported, performed on controlled-purity alloys of type 304L stainless steel irradiated with 3.4 MeV protons to 1 displacement per atom at 400°C. Because of statistical noise and the practical lower limit on the step size in STEM, deconvolution of the measured data does not yield physical results. An alternative analysis of STEM data is presented. Numerical calculations of RIS profiles are convoluted with the instrumental broadening function and modified iteratively to fit the data, yielding a “best estimate” profile. This “best estimate” is convoluted with the Auger intensity profile to yield a simulated AES measurement, which is compared with the actual AES measurement to provide an independent test of the validity of the “best estimate”. For impurities with a narrow segregation profile and an Auger electron escape depth of one monolayer, a combination of STEM and AES data allows a determination of the width of the segregated layer. It is found that, in an ultrahigh-purity alloy doped with P, the latter is essentially contained in a single monolayer.

Auger spectroscopy analysis of palladium silicide films

The formation of Pd2Si in Pd films sputter deposited on Si substrates and heated up to 400 °C has been studied by measuring the depth profile using Auger electron spectroscopy (AES) and Ar+ ion sputtering. Significant chemical effects in the silicon LVV Auger peak shape have been observed, enabling the easy differentiation of the silicide from elemental silicon. The depth profile indicated that the silicide phase is formed at the Pd/Si interface even in the unannealed films. In forming the silicide, the silicon atoms diffuse through the film and on arrival at the surface oxidize to form a thin layer of SiO2. Some of the problems encountered in the determination of the depth scale from the AES data are pointed out.

Oxygen chemisorption on platinum: II. Model calculations

There exist two conflicting sets of data in the literature concerning the sticking probability of oxygen on platinum. One set suggests a large value of the order of 0.1, while other results indicate that the sticking probability is much smaller. Recent Auger electron spectroscopy data of Weinberg et al. yield a value of ca. 7 × 10 −7 on a clean platinum (111) surface. Reasons are given for believing that the large sticking probabilities are measured when the platinum surfaces are contaminated with carbon, and the smaller values are obtained when the platinum is clean. Absolute rate theory of gas phase kinetics together with the Crystal Field Surface Orbital-Bond Energy Bond Order (CFSO-BEBO) Model of Weinberg and Merrill is applied to obtain a theoretical sticking probability of 7 × 10 −6 ⩽ S ⩽ 7 × 10 −5 in reasonable agreement with experiment. The activation energy to chemisorption is predicted to be ca. 2.1 kcal mole . A model is also developed for the case of carbon stimulated adsorption of oxygen on a contaminated surface, and its properties investigated by the same theoretical approach. In the latter case the adsorption is found to be non-activated, but the principal reason for the great increase in the adsorption rate lies in a change in the entropy of activation. Substitution of reasonable numerical values for the parameters in the rate expression leads to a calculated sticking probability of the order of 0.1 for the contaminated surface, i.e. close to the high values reported by several workers.