bluuebunny/crossref_metadata_2025 huggingface dataset:
The space within a profile
Authors: Zipin Richard B.
Published: May 2005

A characteristic of surface texture which is often overlooked by engineers who specify surfaces, but which could be of great importance to them in the tribological analysis of surface profiles, is the space contained within the profile. There are two related parameters which express this characteristic, namely the volume of material in the profile hills, and the volume of empty space in the profile valleys. The former is the volume of material above a specified level within the profile and the latter is the volume of empty space below a specified level, both per unit area of surface. They are measured by the area bounded by a line at the particular level of interest and the profile curve itself, either above or below the line at the level of interest respectively, per unit length along the profile. When they are evaluated at the mean line of the surface profile, their sum is equal to the roughness average which is the most common surface texture parameter specified for engineering surfaces.

These parameters are of significance to tribologists since the volume of material in the surface hills is clearly related to the load carrying capacity and the wear resistance of a surface, while the volume of empty space in the valleys relates to the ability of the surface to retain lubricant and to store debris, all of which are important in applications where contact between surfaces is involved.

The two parameters are studied for deterministic and random surface profiles and their digital implementation is derived. Applications of the analysis presented are discussed.
Electron yields and escape depths from Kapton and Teflon
Authors: Yang Kai‐Yueh , Hoffman R. W.
Published: May 2005

Secondary electron emission (SEE) characteristics, i.e., SEE yield maximum, the electron energy corresponding to the maximum yield, Emax, and crossover energies at which the SEE yield is unity, as a function of angle of incidence were determined for Kapton and Teflon. Photoelectron yield as a function of angle of incidence from Kapton were also determined. Secondary electron escape depth and photoelectron escape depth from Kapton were calcuated from the experimental data.

Pulse beam techniques were used to reduce surface charging problems. Three μsec pulses of electrons were used in SEE experiments, and 100 msec to 1 sec pulses were used in photoemission experiments. The maximum yield of Kapton increases from 1.7 at normal incidence to 3.0 at 80° angle of incidence, Emax increases from 280 eV to 620 eV. The maximum yield of Teflon increases from 2.4 at normal incidence to 3.1 at 80° angle of incidence. The secondary electron escape depth in Kapton was calculated t be 55 ± 5 Å. Photoelectrons excited by 21 eV photons have a 87 ± 30 Å escape depth in Kapton.
In situ interface analysis by ion backscattering/channeling technique using a thin window cell
Authors: Padmanabhan K. R. , Bhowmick S. , Hua Zhang Zu
Published: May 2005

In situ analysis of solid–liquid and solid–gas interfaces by high energy ion backscattering/channeling technique have been investigated. Using thin single crystal windows like that of Si in a specially constructed cell, the backscattered yield and the channeling minimum yield have been utilized to obtain in situ information on solid–gas and solid–liquid interfaces. Examples in the application of this technique to investigate the in situ etching damage at the interface in the dry etching of Si have been given. It is found that XeF2 etching of Si crystal offers a good surface which is relatively free from any visible damage within the limitation of the sensitivity of the RBS analysis. The evidence of an epitaxially grown Cu layer on Si from CuSO4 solution in the thin window cell has been given. These experimental results demonstrate the potential application of this technique in the field of catalysis and electrochemistry.
Ion beam mixing of Pt with René N4 alloy
Authors: Srinivasan V. , Bhattacharya R. S.
Published: May 2005

Ion mixing was studied in Pt‐René N4 alloy system. The substrate, René N4, is a nickel‐base superalloy with about 66% of ordered γ′ precipitates by volume. The average precipitate size is approximately 0.42 μm. Mixing was accomplished by 1 MeV Pt+ ions at two different doses and followed by Rutherford back scattering and Auger sputter profiling. Mixing was significantly slower in this system than it was in Pt/Ni binary alloy suggesting a possible strong influence of alloy chemistry, microstructure or intermediate impurity layer on the mixing process.
High resolution electron microscopy of surfaces and surface reactions
Authors: Smith David J. , Bovin J. O. , Bursill L. A. , Petford‐Long A. K. , Ye H. Q.
Published: May 2005

A 400 kV high‐resolution electron microscope has been used in the surface profile imaging mode to observe surfaces and surface reactions directly in real time. The processes studied include: the formation of surface oxides on Pd and Ag and on In‐compound semiconductors; surface reduction and metallization, diffusion and accretion on oxide surfaces; and structural rearrangements in small metal particles. It is concluded that the technique can provide unique information about surface phenomena.
Application of cross‐sectional transmission electron microscopy in the characterization of ion beam processed materials surfaces
Authors: Rai A. K. , Bhattacharya R. S. , Pronko P. P. , Tai‐il‐Mah
Published: May 2005

Ion‐beam‐mixing‐induced amorphization of NiTi bilayered thin film and the amorphization of α‐SiC through ion bombardment have been studied by employing cross‐sectional transmission electron microscopy techniques. Rutherford backscattering analysis was employed to monitor the mixing of NiTi bilayer as a function of dose (3 × 1015−2 × 1016 ions cm−2) of 1 MeV Au+ ions. It has been observed that amorphization starts at the interface as the mixing proceeds. Formation of a buried amorphous layer was obtained in α‐SiC by ion bombardment with 2.5 MeV Ni+ at a dose of 1 × 1016 ions cm−2. Double energy implants (1 MeV Ni+, 1 × 1016 ions cm−2+2 MeV Ni+, 1 × 1016 ions cm−2) were employed to obtain 1.8 μm thick continuous amorphous layer on the surface of α‐SiC. Also, in the present investigation, it has been shown that α‐SiC pieces with amorphous surface layers joined better than those with as received crystalline surface layers.
Investigation of resin–substrate interactions: An IETS study of phenol‐ and cresol‐ formaldehyde model compounds
Authors: Brown N. M. D. , Meenan B. J. , Affrossman S. , Pethrick R. A. , Thomson B.
Published: May 2005

The IET spectra of a number of phenol‐like, cresol‐like and methylolated ‘phenols’ are reported. These molecules are used as models of certain of the structural units found in a typical Novolac phenol–formaldehyde resin system. It is found that these poly‐phenolic molecules adsorb an aluminium oxide in predominantly the form of phenolate anions. In the case of those molecules in which the phenolate is associated with ortho‐methylol groups a site‐specific adsorption and a local near‐perpendicular alignment at the oxide surface is proposed. The spectra found also show that the formation of chemisorbed phenolate anion(s) occurs with adsorbate deprotonation and reaction with surface hydroxyl groups, with this latter process forming water which is then desorbed. The ease of this reaction suggests that the reverse process may be related to the loss of adhesion when a joint structure is exposed to water vapour.
Imaging XPS—a new technique. 2—Experimental verification
Authors: Gurker N. , Ebel M. F. , Ebel H. , Mantler M. , Hedrich H. , Schön P.
Published: May 2005

The XPS image is obtained by the dissection of the surface area of interest into a series of adjacent narrow strips. The width of the entrance slit system of the energy analyzer gives the strip width and a translational movement of the specimen makes it possible to investigate the total number of strips step by step. By means of the double focusing properties of the spherical analyzer the energy spectrum from each point (spot) of the strip area under observation is available on the detector focal plane. Specific photoelectron lines are selected by a suitable choice of the sphere voltages. A position sensitive electron detector together with a computer is used to collect and store these spectra simultaneously in the course of one measurement. The net count rate is evaluated afterwards. Each spot of the strip is represented by its corresponding value of the net count rate and the series of values is stored in a computer memory. At the end of collection of all the strip information the image is put together strip by strip. To date a resolution of 0.3 mm has been realised and the time of data collection for an area of 10 × 10 mm2 is about one hour. The corresponding time of measurement with our imaging method is just a few minutes as one needs only the elemental distribution of an element along a single line as in an electron micronalyzer with a line scan.
Surface segregation and preferential sputtering in CoNi alloys: Computer simulation of Auger spectra
Authors: Hajcsar E. E. , Dawson P. T. , Smeltzer W. W.
Published: May 2005

The phenomena of surface segregation and preferential sputtering have been investigated in the CoNi alloy system where previous results have been contradictory. Six alloys covering the whole solid solution range were annealed at 853 K and quenched to give equilibrium segregated surfaces. Computer simulation methods were employed to analyze spectra in both energy windows significant to the system and results are reported with explanations of previous discrepancies. Shown is the fact that Ni both preferentially sputters and segregates over the whole composition range. The segregation is only truly obvious in low energy (M2,3M4,5M4,5 transisitions) spectra as it is a monolayer phenomenon and higher energy peaks are not surface sensitive enough.
A review of the surface tension of silicon and its binary alloys with reference to Marangoni flow
Authors: Keene B. J.
Published: May 2005

High quality single crystals of silicon required by the electronics industry are produced in bulk by crystal‐growth‐from‐the‐melt techniques. Temperature and concentration gradients at the free surface of the melt will give rise to surface tension‐driven flow (Marangoni flow), which, if sufficiently large, can lead to crystal defects in the end‐product. The relevance of the liquid surface properties to Marangoni flow is discussed. Published data for the surface tension of silicon and its binary alloys have been collated. Analysis of the data suggests that many of the results quoted for the surface tension of silicon may refer to material contaminated with oxygen. None of the solutes in the binary melts exhibits significant surface‐activity in silicon. Potentially important systems, for which there are no data, have been identified.
SIMS and XPS studies of polyurethane surfaces 2. Polyurethanes with fluorinated chain extenders
Authors: Hearn M. J. , Briggs D. , Yoon S. C. , Ratner B. D.
Published: May 2005

A series of fluorine‐containing segmented poly(ether urethanes) and poly(ether urethane ureas), previously characterized by angular dependent x‐ray photoelectron spectroscopy (XPS) have been re‐examined using static secondary ion mass spectrometry (SIMS). Comparison of the data from the two techniques has shown that the intensity of secondary ion signals which characterize the hard and soft segments can be used quantitatively for direct analyis of the molecular composition at the surface. Moreover, the SIMS sampling depth for the conditions used has been shown to be ∼ 10 Å, significantly less than the XPS sampling depth under normal conditions, and similar to the XPS sampling depth at high glancing take‐off angle (with respect to the surface normal).
Quantitative sputtering
Authors: Zalm P. C.
Published: May 2005

This review discusses experimental techniques used for determining the variety of observables in ion‐bombardment induced erosion of solid surfaces. Boundary conditions for performing reproducible and accurate sputtering yield measurements are formulated. To this end, an inventory is made of the observed systematics in several phenomena accompanying sputtering and of the more regular exceptions to the general trends, also, a brief treatment of some theoretical predictions is given, based on the available literature. Following this extensive survey, the merits and limitations of a number of measurement methods, tailored to study one or more different observables, are discussed. Techniques that seem widely applicable or highly promising are emphasized.
Corrosion of stellite‐6 in lithiated and borated high‐temperature water
Authors: Hocking W. H. , Lister D. H.
Published: May 2005

Corrosion of the cobalt‐based alloy Stellite‐6 in lithiated and borated water at 300°C with a hydrogen overpressure has been investigated. These conditions simulate a well‐defined chemistry regime in the primary circuit of an operating pressurized water reactor. The resulting oxide films were characterized using a combination of surface analytical and electron microscopy techniques. X‐ray photoelectron spectroscopy (XPS) was employed to evaluate the chemical composition of the oxide films. The morphology of the corroded surfaces was revealed by transmission and scanning electron microscopy. Scanning Auger microscopy (SAM) was used to map the distribution of elements within the oxide and underlying alloy layers. Composition depth profiles were determined by sequential ion‐sputter etching in conjunction with either XPS or SAM surface analysis. Although some differences exist, the oxide films are qualitatively similar to those described for exposure of Stellite‐6 to lithiated high‐temperature water in the absence of boron. In both cases, preferential dissolution of cobalt leads to strongly enhanced chromium concentrations within the oxide films.
Use of EN(E) spectra for quantitative AES analysis of AuCu alloys
Authors: Ichimura S. , Koshikawa T. , Sekine T. , Goto K. , Shimizu H.
Published: May 2005

The possibility of quantitative AES analysis using the whole EN(E) spectrum was examined for AuCu alloy samples. The EN(E) spectrum was measured under φ = 0° (normal) incidence of 10 keV electrons for the Au–44 at% Cu sample, and under φ = 0°, 30°, and 45° incidence of 10 keV primary electrons for the Au–20 at% Cu sample. Those spectra were compared with spectra which were obtained by linear combination of pure Au and Cu spectra measured under the same experimental conditions.

Both measured and synthesized spectra coincided very well in the energy region lower than 1000 eV, except the region of slow secondary electrons. The results indicate that energy distribution of backscattered electrons of the AuCu alloy can be estimated well by linear combinations of pure sample spectra. They also indicate that, by comparison of the shape of the measured EN(E) spectrum with the synthesized one, the surface composition of the AuCu alloy sample can be estimated with reasonable accuracy (several % error).
The development of standards for surface analysis
Authors: Powell C. J.
Published: May 2005

As the use of surface analysis increases, the need for standards (reference procedures, reference data, and reference materials) becomes more urgent. This article describes recent activities and current plans of three organizations that are active in developing standards for surface analysis: Committee E‐42 on Surface Analysis of the American Society for Testing and Materials; the Surface Chemical Analysis Working Party of the Versailles Project on Advanced Materials and Standards (VAMAS); and the Working Group on Surface Analysis of the International Union of Pure and Applied Chemistry.
X‐ray spectrometry and photoelectron spectroscopy applied to the study of layered samples: SiO2 and SiOx films on InSb
Authors: Packwood R. H. , Remond G. , Holloway P. H.
Published: May 2005

X‐ray spectrometry in the electron probe micro‐analyzer (EPMA) and x‐ray photoelectron spectroscopy (XPS‐ESCA) are used to study the composition of SiOx(1 < x ≤ 2) films of known thicknesses over InSb substrates. The analyses of SiO2 surface layers demonstrate the credibility of the model which was developed to predict the x‐ray emission in the EPMA from a surface layer on a substrate. X‐ray data indicate the presence of two chemical states in the SiOx film while three states are detected from XPS data. Both EPMA and ESCA data indicate that the SiOx compound has a composition equivalent to SiO1.12.
Electron attenuation lengths in Pb metal
Authors: Chadwick D. , Christie A. B. , Karolewski M. A.
Published: May 2005

Electron attenuation lengths have been measured for Pb metal in the energy range 300–1200 eV. The measurements were carried out by observing the attenuation produced in a substrate (Cu, Ag or Pd) XPS signal following adsorption of a single Pb monolayer. Attenuation lengths were estimated from these attenuation factors by means of a Lambert–Beer expression. The data are represented well by the least–squares expression λ = 0.78(±0.08)E1/2 (in Å).
Characterization of PdCl2/SnCl2 metallization catalysts on a polyetherimide surface by XPS and RBS
Authors: Burrell Michael C. , Smith Gary A. , Chera John J.
Published: May 2005

A metallization catalyst (based on the PdCl2/SnCl2 system) adsorbed on polyetherimide surfaces was characterized by x‐ray photo‐electron spectroscopy (XPS), Rutherford back scattering (RBS) and transmission electron microscopy (TEM). The overall Pd/Sn ratio increased from 0.2 to 3.8 when the initial sensitized surface was treated with the accelerator solution. XPS results indicated that before acceleration, only Sn(IV) (stannic hydroxide) is obserable, and after acceleration both metallic Sn and Sn(IV) are present; palladium is present primarily in a metallic form both before and after the accelerator step. Total Pd and Sn coverages were also obtained by RBS, and the total Pd/Sn ratios agree with the XPS surface measurements for specimens just prior to metallization. TEM micrographs showed the adsorbed catalyst consisted of particles 10–50 Å in size covering only a fraction of the surface.
Technique of sequential surface analysis with ISS and AES
Authors: Shimizu Ryuichi
Published: May 2005

The development of a new approach is briefly described, which enables Auger electron spectroscopy (AES) and ion scattering spectroscopy (ISS) to be performed sequentially with a commercial‐type Auger microprobe. These sequential AES and ISS measurements were applied to depth composition analysis of the altered layer formed in the surface of AlMg(60 at%) alloy under ion bombardment. A simple analysis has suggested that the ion bom‐bardment forms an altered layer in the surface, which consists of Mg‐rich composition at the top‐most atomic layer, followed by the depletion layers of Mg atoms extending over a few tens of atomic layers deep.
An NBS standard reference material for depth profile analysis
Authors: Fine Joseph , Navinšek Boris
Published: May 2005

A periodically modulated thin‐film material, specifically developed for calibrating sputtered depths and erosion rates, is available from NBS. Information on its structure and characterization is summarized.
Direct observation of pesticides on plants using LAMMS: Imazaquin on soybean leaves
Authors: Brinen J. S. , Los M. , Kelland D. , Wallach E. R.
Published: May 2005

LAMMS (Laser Microprobe Mass Spectrometry) has been used to observe the presence and location of a herbicide on plant lea, es. Leaves from soybean plants, sprayed with imazaquin, a member of the imidazolinone class of herbicides, at varying application rates, were examined by LAMMS without any special preparation. A rapid analysis for imazaquin was obtained confirming the suitability of LAMMS as an organic microprobe analyser. A comparison with standard chemical ionization and electron impact mass spectra of imazaquin showed evidence for laser‐induced fragmentation.
Calculations of electron inelastic mean free paths for 31 materials
Authors: Tanuma S. , Powell C. J. , Penn D. R.
Published: May 2005

We present new calculations of electron inelastic mean free paths (IMFPs) for 200–2000 eV electrons in 27 elements (C, Mg, Al, Si, Ti, V, Cr, Fe, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au and Bi) and four compounds (LiF, SiO2, ZnS and Al2O3). These calculations are based on an algorithm due to Penn which makes use of experimental optical data (to represent the dependence of the inelastic scattering probability on energy loss) and the theoretical Lindhard dielectric function (to represent the dependence of the scattering probability on momentum transfer). Our calculated IMFPs were fitted to the Bethe equation for inelastic electron scattering in matter; the two parameters in the Bethe equation were then empirically related to several material constants. The resulting general IMFP formula is believed to be useful for predicting the IMFP dependence on electron energy for a given material and the material‐dependence for a given energy. The new formula also appears to be a reasonable but more approximate guide to electron attenuation lengths.
SSIMS and SIMS imaging analysis of a drug delivery system
Authors: Davies M. C. , Brown A. , Newton J. M. , Chapman S. R.
Published: May 2005

The surface chemical analysis of a polymeric drug delivery system has been undertaken using secondary ion mass spectrometry (SIMS). The molecular specificity of static SIMS is demonstrated by the detection of the molecular ion of the drug and its principal fragments within the polymer surface in both positive and negative ion modes. SIMS imaging of molecular ions specific to the drug illustrate its uniform lateral distribution in the interfacial polymer surface network.
Texture of Raney Ni catalysts: Al‐leaching out of rapidly solidified Ni2Al3 alloys
Authors: Gros J. , Hamar‐Thibault S. , Joud J. C.
Published: May 2005

Raney catalysts are prepared by removing Al out of NiAl alloys in boiling NaOH. The evolution of the microcrystallized Ni2Al3 structure during Al‐leaching out is essentially studied by transmission electron microscopy. The different phases of the precursor microcrystallized alloys are attacked selectively. Moreover, Al‐leaching out of Ni2Al3 occurs step by step. The Ni crystallites' orientation is directly related to the orientation of precursor alloys. An intermediate phase of Ni2Al type was observed. AES experiments were also performed before and after Al‐leaching out of undoped and Cr‐doped alloys.
LMIS‐SIMS studies of oxide scales
Authors: Moon D. P.
Published: May 2005

A spatial resolution of <0.1 μm can be routinely achieved in secondary ion mass spectrometric analyses following the introduction of the liquid metal ion source. This has proved a powerful tool for investigating the processes of scale growth during the corrosion of metals and alloys at high temperatures. Secondary ion imaging has indicated that oxygen (tracer) transport in fine‐grained NiO scales occurs both by solid‐state diffusion along grain boundaries and by gaseous diffusion through cracks/pores. Dispersions of ceria particles in NiO scales promote oxygen penetration.
Simple angle‐resolved auger electron spectroscopy system—effective rule for measurement and tests of possibilities
Authors: Mróz A. , Mróz S. , Zagórski M.
Published: May 2005

An angle‐resolved Auger electron spectrometer, containing an immovable collector of electrons placed behind the hole in the fluorecent screen of the LEED optics and an electron gun fastened to the sample holder and rotating together with this sample was constructed and tested.

Conditions enabling the best angular resolution, the effective rule for the measurement procedure with the use of microcomputer for controlling the measurement and storage and evaluation of the results, and a simple method of deconvolution of AES angular profiles are proposed.

A result of testing measurements of polar angle‐resolved Auger electron spectroscopy (ARAES) profile for the nickel (001) face is presented.
Transfer and treatment of AES, XPS and SIMS data with a network computer station
Authors: Mathieu H. J. , Mischler S. , Vogel A. , Seiler A. , Riedl G.
Published: May 2005

Surface and interface data by AES, XPS and SIMS are acquired either by a PDP 11–34, HP 9836U or HP 310 microcomputer using commercially available software (ESAU‐Perkin Elmer written in ASSEMBLER) or laboratory‐written software (HP BASIC version 3.0/4.0), respectively. These data are then transferred to an independent Apollo computer network station to allow off‐line treatment of the experimental data. This paper reports on the standardization of the data output files of the acquired data and their subsequent transfer and reading by an Apollo Network DN 3000 station. The program for the Apollo computer written in C‐language allows data treatment as smoothing, differentiation, integration, normalization, curve‐fitting and deconvolution on one hand, but also manipulation of data, like calculation of atomic concentration referring to tables based on handbook data. All data can be stored in a format allowing later use for data banks.
Matrix dependence of elastic scattering effects in quantitative AES and XPS
Authors: Jablonski A. , Lesiak B. , Ebel H. , Ebel Maria F.
Published: May 2005

An involved Monte Carlo algorithm has been developed for simulating the Auger electron and photoelectron trajectories in the surface region of different materials. The partial wave expansion method was applied to describe the electron elastic scattering. Extensive calculations were performed for C 1s photoelectrons emitted from carbon implanted in a number of materials with atomic number varying from 6 to 79. It has been found that elastic collisions influence considerably the angular distribution of photoelectrons. The asymmetry parameter describing the actual distribution decreases owing to photoelectron elastic scatering. This effect becomes more pronounced with increase of atomic number of a matrix. Two correcting parameters in quantitative XPS formalism are proposed to account for elastic scattering effects. The analytical expressions are determined to describe these correcting parameters as a function of (i) matrix atomic number, (ii) matrix atomic density, and (iii) radiation used.

Similar analysis was made for carbon KLL Auger transition. Elastic Auger electron collisions were demonstrated to decrease up to 15% the Auger signal intensity. No distinct changes in angular distribution of Auger electrons were observed. An analytical expression was fitted providing the signal intensity decrease as a function of matrix atomic number and atomic density.
Ion beam induced roughness and its effect in AES depth profiling of multilayer Ni/Cr thin films
Authors: Barna A. , Barna P. B. , Zalar A.
Published: May 2005

The development and changes in the surface topography during ion beam etching is described by a new model taking into account the lateral displacement and collective behaviour (annihilation) of the ‘macrostep’.The model was applied to simulate thedepth dependent surface roughening taking place at the depth profiling of Ni/Cr multilayer systems with various sputtering conditions. Crystals in a channelling position were considered as sources of macrosteps. The experiments confirmed the lack of the surface roughening predicted by the model at high incidence angle of the ion beam (θ>85°)and at sample rotation. The experimental depth resolution proved to be independent of the depth if the upper layers had been removed by presputtering in ion milling equipment at θ = 86° before the conventional Auger depth profiling was carried out. A best resolution‐ (3.2 nm) has been achieved at 225 nm depth when the sample was presputtered down to 180 nm and was also rotated during Auger profiling.
Surface characterization of the deactivation of alumina catalysts used for COS synthesis
Authors: Mink G. , Bertóti I. , Németh L. , Gáti G. , Mohai M. , Székely T.
Published: May 2005

One of the possible routes of producing COS, an important material in organic synthese, is the CO2 + CS2 ⇄ 2COS reaction, preferably over gamma‐alumina catalysts. Under long‐term loading, however, a remarkable loss of the catalytic activity occurs.

The nature of the ageing process was studied by a multi‐technique apporach on high purity [I] and on a commerical grade [II] gamma‐alumina, which latter contained Na, Ca, and S as surface impurities.

On catalyst [I] weak chemisorption of CO2, CS2 and COS was observed by the volumetric method, as characterized by the isosteric heats of adsorption. Catalyst [II] chemisorbed CO2 and COS but not CS2 and showed much less catalytic activity. Gravimetric measurements have shown that adsorption of CS2 and COS leads to the surface deposition of side products. XPS studies on new, loaded and aged samples have revealed that the ageing of the catalyst is primarily caused by the deposition of sulphur and carbon with carbon in excess, presumably in CS, CS and CC environements.
The influence of Y on the structure and growth mechanism of alumina scales
Authors: van Manen P. A. , Young E. W. A. , Schalkoord D. , van Der Wekken C. J. , de Wit J. H. W.
Published: May 2005

Small additions of yttrium to NiAl result in a decreasing oxygen transport through the Al2O3 scale on AiAl at 1270 K, as has been shown by nuclear reaction analysis (18O(p, α)15N). A higher concentration, e.g. 0.5 wt%, has the opposite effect. Yttrium segregates to the grain boundaries in the alloy, and an enhanced Y concentration has been observed by means of EPMA in the oxide scale above the grain boundaries of the alloy. Transition aluminium oxides are shown to be formed in the initial stage at 1170 K with (glancing angle) x‐ray diffraction. Only α‐Al2O3 is formed after oxidation for several minutes at higher temperatures (1470 K). The rate of transformation of transition Al2O3 to the stable α‐Al2O3 modification depends on the oxidation temperature. The transition is shown to be retarded by the presence of Y. The primary transport processes in the Al2O3 scales are short‐circuit diffusion of oxygen and/or aluminium. At 1170 K, while transition oxides are still present, Al transport predominates. At higher temperatures, when the oxide has the α‐Al2O3 structure, oxygen transport is enhanced. This would also explain the retardation of oxygen transport by the addition of Y, since Y was found to prevent the formation of the most stable form of Al2O3.
Secondary ion emission of α‐brass alloys. The chemical effect on the ionization yield of copper and zinc
Authors: Darque‐Ceretti E. , Delamare F. , Blaise G.
Published: May 2005

Ionization yields of copper and zinc in α‐brass alloys are determined at an oxygen pressure P = 1.5 × 10−5 Torr. Two interpretations of the results are proposed, according to the bond breaking model and to the statistical environment model. The second one gives better agreement with experimental values.
Quantification of sputter depth profiles by means of wedge crater sputtering—a new technique for depth scale calibration
Authors: Voigtmann R. , Moldenhauer W.
Published: May 2005

An essential part of depth profile quantification is the conversion of sputtering time into depth, for which a simple method is described. It requires an ion gun providing a sufficient fine focusable ion beam. A suitable beam control produces a wedgelike distribution of ion current density in a raster field which is large compared to the ion beam cross‐section. A “wedge crater” is sputtered in this way in addition to the “normal crater” for depth profiling. The wedge crater profile obtained of surface profilometer measurements provides the sputtering time–depth relation. Moreover the sputtering rate as a function of depth may be deduced from wedge crater profile. Application of the method to SIMS depth profiling in multilayer thin film systems shows its usefulness in depth scale calibration and intensity correction. Small expenditure and universal applicability are advantages in comparison with other methods.
XPS intensity analysis for assessment of thickness and composition of thin overlayer films: Application to chemically etched GaAs(100) surfaces
Authors: Bernstein R. W. , Grepstad J. K.
Published: May 2005

Quantification by XPS intensity analysis of thin multicomponent overlayers, like the native oxides forming on compound semiconductor surfaces, is discussed in some detail. In particular, the advantage of exploiting the attenuated emission from substrate core levels with different probing depths is emphasized, in order to obtain a precise measure for the overlayer thickness dimension. For GaAs(100) treated with different chemical etches, estimates are obtained for the thickness of the native surface oxide formed after exposure to air, of 6–8 Å. The elemental composition of the surface oxide is close to the stoichiometric metal: oxygen ratio of the bulk oxides Ga2O3 and As2O3, in perfect agreement with the measured core‐level shifts (1.4 ± 0.2 and 3.0 ± 0.1 eV for the Ga and As 2p levels, respectively). On a CF4 plasma‐etched sample, a surface reaction layer of gallium fluoride was found with a composition close to GaF2 and an estimated thickness of ∼23 Å. This paper also discusses how to determine the kinetic energy dependence of the electron escape depth, expressed in terms of an exponent m (γ Em), by working out consistent estimates for the surface oxide (fluoride) thickness via two different approaches. Values for m are obtained in the range 0.5–0.6, in excellent agreement with previously reported data on electron escape depth for semiconductors.
XPS and UPS examinations of the formation of passive layers on Ni in 1 M sodium hydroxide and 0.5 M sulphuric acid
Authors: Hoppe H.‐W. , Strehblow H.‐H.
Published: May 2005

The passivation of nickel has been studied in 1 M NaOH and 0.5 M H2SO4 by XPS. An electrochemical specimen preparation and transfer to an ultra‐high vacuum, without contact with oxygen, permits a detailed examination of the oxide growth with potential and time resolution. Quantitative evaluation of the data yields values for the thickness of the partial layers of the duplex film structure. The Ni/NiO/Ni(OH)2 sequence for the passive range and Ni/NiO/NiOOH sequence for the transpassive range in alkaline solutions have been confirmed by a detailed peak analysis, including angular‐dependent XPS measurements. These results are closely related to the polarization curves. An interpretation is given on the basis of a simple semiconductor model involving the results of UPS and work function measurements. The data of the acidic and the alkaline electrolytes are related to each other and their differences are explained by the increased solubility for low pH of the outer Ni(OH)2 and NiOOH layers, respectively. These properties cause thinner films in acidic electrolytes and prevent the formation of a stable NiOOH overlayer for these conditions.
A proposed standard (PTFE tape) for static SIMS
Authors: Briggs D.
Published: May 2005

The requirements for a viable standard material for the assessment of the performance of static secondary ion mass spectrometers are discussed. PTFE (polytetrafluoroethylene) tape appears to be a suitable candidate for assessing the absolute sensitivities of the instrument for both positively and negatively charged species, as well as assessing the charge compensation ability for insulators. An experimental procedure is described and representative spectra obtained under well‐defined conditions are presented.
Chemical reactions and temperature‐dependent interface formation of Ti/InP (110)
Authors: Chassé Th. , Wilke W. G. , Horn K.
Published: May 2005

The reaction of a clean InP(110) surface with thin layers of titanium, deposited at room temperature and 140 K, was studied by core‐ and valence‐level photoemission. We were able to identify reacted interface species by means of curve‐resolving of high‐resolution core‐level spectra. It was found that titanium reacts strongly with InP(110), leading to a reacted layer of ∼9–12 Å thickness, which consists of a TiP compound. In this process, indium is liberated from the substrate and forms metallic islands in the surface region. Further deposition leads to the formation of a metallic Ti film, into which the indium is alloyed. On the basis of annealing experiments, we were able to identify the reacted zone as a diffusion barrier for further interface reaction. The reacted zone was found to broaden at elevated temperature. Our data are discussed with respect to studies of other transition metals with InP(110) and III–V semiconductor surfaces.
Use of the direct energy spectra in Auger electron spectroscopy
Authors: Langeron J.‐P.
Published: May 2005

The approach to quantitative AES via background subtraction is discussed. Because the knowledge of the transmission function is very important, a possible method for its determination is described. Respective contribution of primary, secondary and inelastic Auger electrons to the background are then theoretically assessed and application to the evaluation of peak‐to‐background and tail‐to‐peak ratios is briefly outlined. A method to normalize the spectra intensities using the background is presented. Finally, spectra combination is proposed as an alternative to background subtraction for quantitative AES. This last method provides information on in‐depth homogeneity and chemical effects.
Quantitative AES and RBS depth profiles of titanium silicide films on GaAs after annealing
Authors: Clement M. , Sanz J. M. , Martínez‐Duart J. M.
Published: May 2005

Quantitative RBS and AES depth profiles of TiSi2 contacts deposited on GaAs by co‐sputtering in a magnetron system have been performed. The bulk composition and thickness of the films were determined by RBS. AES showed that some oxygen was incorporated in the silicide layer during the deposition procedure. Comparing the depth profiles provided by both techniques, preferential sputtering effects have been studied. It is shown that silicon is preferentially sputtered as a consequence of its segregation to the surface. Sputter yields of the compound (YTiSi2 = 2.85 atoms ion−1) and of the individual components (Y = 2.5 atoms ion−1 and Y = 3.1 atoms ion−1) were also estimated for 3‐keV Ar+ ions. Important interdiffusion effects appear to occur at annealing temperatures above 600°C. It is also observed that As has a higher mobility than Ga in TiSi2 when annealed at 800°C.
XPS studies of the fluoride ion‐selective electrode membrane LaF3: Evidence for a gel layer on the surface
Authors: De Marco R. , Hauser P. C. , Cattrall R. W. , Liesegang J. , Nyberg G. L. , Hamilton I. C.
Published: May 2005

XPS has been used to examine the surface of the fluoride ion‐selective electrode membrane. It has been found that water chemisorbs onto the surface of the LaF3 crystal. Surface degradation products were found on the LaF3 membrane after prolonged exposure to water. It is proposed that these products influence the time taken to obtain stable electrode potentials. The effect of solutions of low pH on the response of the fluoride electrode has been studied, and a mechanism for their action is proposed. As is the case for glass‐electrode membranes, a gel layer has also been observed on the surface of LaF3.
Modulated interfacial disorder scattering in quantum wells and its device applications
Authors: Bhobe Suyog , Porod Wolfgang , Bandyopadhyay Supriyo , Kirkner David J.
Published: May 2005

We investigate the nature of the electronic states and transient transport in a single, selectively doped, GaAs quantum well where the dopants are confined near one of the interfaces. The electronic states are calculated from self‐consistent solutions of the Schrödinger and Poisson equations and are used to compute the scattering rates for electrons interacting with the dopants. These scattering rates are then used in a Monte Carlo simulation to study the time‐dependent decay of the momentum of an ensemble of electrons traveling parallel to the interface.

We also investigate the momentum relaxation of electrons injected into the well under different transverse electric fields that skew the wavefunction towards one of the interfaces. When the wavefunction is skewed away from the doped interface, the momentum relaxation time (and hence the mobility) increases dramatically by three orders of magnitude. A device application of this phenomenon, namely the operation of a velocity modulation transistor (VMT), has been investigated, with special focus on the transistor's switching speed.
Elastic scattering and quantification in AES and XPS
Authors: Jablonski Aleksander
Published: May 2005

In the mathematical formalism of quantitative AES and XPS, the elastic electron collisions are not taken into account. However, recent calculations have shown that the neglect of the elastic collisions may result in considerable errors. Theoretical analysis of the actual electron transport in a solid requires two major problems to be considered. (i) calculation of the differential elastic scattering cross‐sections for a given potential and electron energy and (ii) description of the multiple electron scattering. Both problems are extensively reviewed. The Monte Carlo method is usually used to describe the electron trajectories in a solid at energies of surface‐sensitive electron spectroscopies. Such simulations have indicated that the elastic collisions of photoelectrons affect considerably the angular distribution of the measured intensity and the photoelectron escape depth. The latter parameter may be diminished by > 30%. Elastic collisions of Auger electrons decrease the current recorded by the typical analysers and also considerably decrease the escape depth. Thus, the actual electron transport in a solid should be considered in calculations associated with determining the inelastic mean free path using the overlayer method or overlayer thickness measurements. The usual formalism of quantitative AES and XPS can be extended easily to account for the elastic electron collisions. The values of the corresponding correcting factors are extensively compiled. To check the validity of the Monte Carlo calculations, the results of simulations of forward electron scattering and electron back‐scattering are compared with the available experimental data. Excellent agreement between experimental and theoretical angular distributions of photoelectrons has been found. A very good agreement was also observed in the case of elastic electron back‐scattering from surfaces.
Angular dependence of sputtering yield of TiSi2 layers and analysis of titanium disilicide by SIMS and SCANIIR methods
Authors: Antonov S. L. , Valiev K. A. , Vasiliev A. G. , Orlikovsky A. A.
Published: May 2005

The values of sputtering yields of TiSi2, Ti and Si layers are determined for Ar+ (8 keV) bombardment at angles 0–80°. It is shown that the theoretical functions that we have suggested for TiSi2 sputtering yields from angular Ar+ bombardment, which are based on models of bicomponent compounds sputtering under normal ion bombardment, are in good agreement with the experimental curve for TiSi2.

The calibration curves for the determination of TiSix layer compositions by SIMS and SCANIIR methods (in dynamic regime) are presented. It is shown with the help of the static SIMS method (E = 3 keV) that not only can the TiSix composition be determined but the TiSi2 crystal phase can also be identified.
Resonance ionization of neutral atoms with applications to surface science, noble gas detection and biomedical analysis
Authors: Thonnard N. , Parks J. E. , Willis R. D. , Moore L. J. , Arlinghaus H. F.
Published: May 2005

Resonance ionization of neutral atoms using narrow‐band tunable lasers to stepwise excite through one or more energy levels, and leading to photoionization, is becoming recognized as an emerging analytical technique having a number of unique properties. These include very high sensitivity, as saturated ionization in a well‐defined volume is possible for most elements, very high element selectivity in the ionization process, as energy levels are unique to each element, and generality, enabling ionization of all elements in the periodic table except He and Ne. In solid‐source mass spectrometry, resonance ionization spectroscopy is a post‐ionization technique, thereby achieving significant advantages by the separation of ionization from atomization.

Combining resonance ionization with mass spectrometry has enabled measurements that heretofore were not feasible. The technique is being applied to a variety of new analytical problems and is showing significant promise. By combining ion sputtering with resonance ionization of the preponderant neutral population, more quantitative measurements are possible of semiconductor materials, especially at surfaces or interfaces. For biomedical applications, the high ionization efficiency, coupled with the high selectivity, allows accurate trace element determinations using microliter‐sized samples. Noble gas analyses have become possible from samples containing only a few thousand krypton atoms. Examples from each of the above application areas will be discussed.
Post‐implantation as an aid in scale calibration for SIMS depth profiling
Authors: Zalm P. C. , Janssen K. T. F. , Fontijn G. M. , Vriezema C. J.
Published: May 2005

It is shown that low‐dose energetic ion implantation may greatly facilitate relative and even absolute depth‐scale calibration for SIMS depth profiling. Sample implantation has to follow all the processing steps to be investigated. The implantation conditions, such as species, fluence and energy, preferably have to be optimized for the particular problem at hand. Then the distribution profile of the implant is to be treated as a two‐dimensional marker, useful both for depth as well as for concentration calibration. A simple practical example demonstrates the power of the method.
Analysis of insulating specimens with the Cameca IMS4f
Authors: Migeon H. N. , Schuhmacher M. , Slodzian G.
Published: May 2005

The normal incidence electron gun of the IMS4f is unique in design, allowing self‐compensation of electric charges when negative secondary ions are analysed. This is made possible owing to the formation of a cloud containing an excess of very‐low‐energy electrons above the sample surface. When positive charges appear at the sample surface, the sample will take out of the colud the exact amount of electrons required for compensation. The effectiveness of this self‐compensation is demonstrated by the analysis of bulk insulators, such as alumina and silicon nitride, as well as multilayered specimens.

In the positive mode, exact adjustment of the electron intensity monitored by the energy distribution of secondary ions allows one to reach a state where the elecric field inside the sample is small enough to make it possible to analyse very mobile elements, such as Li and Na, without migration. Misadjustment of the electron intensity will create an electric field at the surface and an equilibrium is observed owing to conduction currents.
Structural characterization of supported chromium clusters by extended energy‐loss fine structure
Authors: Lozzi L. , Passacantando M. , Picozzi P. , Santucci S. , Diociaiuti M. , Paoletti L.
Published: May 2005

The lattice parameters of chromium clusters deposited on carbon substrates were determined by extended energy‐loss fine structure (EXELFS) measurements in transmission mode beyond the L2, 3 edges of chromium using an electron microscope. Fourier analysis of the data shows a sizeable lattice parameter contraction when the mean diameter of the clusters decreases. This contraction amounts to ∼5.2% with respect to the bulk value for those clusters with a mean volumetric diameter of ∼13 Å. The behaviour of the nearest‐neighbour‐distance contraction versus cluster diameter agreed with a macroscopic liquid‐drop model.