bluuebunny/crossref_metadata_2025_split huggingface dataset:
A proposed standard (PTFE tape) for static SIMS
Authors: Briggs D. 
Published: May 2005

AbstractThe 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

AbstractThe 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

AbstractThe 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

AbstractQuantitative 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

AbstractXPS 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

AbstractWe 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

AbstractIn 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

AbstractThe 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

AbstractResonance 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

AbstractIt 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

AbstractThe 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

AbstractThe 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.
Helium ion and fast atom scattering from polycrystalline copper surfaces
Authors: Xu N. S. , Sullivan J. L. 
Published: May 2005

AbstractLow‐energy ion scattering from surfaces is an established technique that gives unique information from the first one or two atomic layers on a surface. The standard technique employing an electostatic analyser, however, has some disadvantages. It detects only scattered ions whose yield from surfaces is relatively low and thus high incident ion fluxes must be used. A high flux of ions will change the nature of the surface in a number of ways. It will lead to significant preferential sputtering and to charging effects, particularly in insulating and semiconducting samples. It has been shown also that ions produce more chemical damage in surfaces that do neutrals of the same energy and species. Many of these disadvantages may be overcome if neutrals are used as the bombarding particles instead of ions.Conventional electrostatic methods cannot be employed to detect neutral sacttered spectra. Hence, a time‐of‐flight mass spectrometer with a pulsed ion/fast atom source (energy range 100–5000 eV) has been developed. This instrument has been used to measure the energy of particles scattered from a polycrystalline copper surface bombarded with either ions or fast atoms. In this study, spectra of He scattered from both ‘ion‐cleaned’ and ‘ion‐cleaned and heated’ copper surfaces were monitored for incident angles ranging from 5° to 75° with a constant scattering angle of 90°. For the ‘ion‐cleaned’ surfaces, spectra of both ion and neutral projectiles show that the technique is sensitive to the outermost surface atomic layer, but that fast atom bombardment seems the more surface specific. For the ‘ion‐cleaned and heated’ surface, spectra for both projectiles are qualitatively identical and first‐order effects can be accounted for by the single binary collision model; however, small but significant differences in peak energy were observed and these may be explained in terms of inelastic collision processes.
Novel chromium layers formed by nitrogen‐ion implantation of conventional and ABCD electrodeposited films, part 4
Authors: Ferber Hermann , Hoflund Gar B. , Mount Charles K. , Hoshino Shigeo 
Published: May 2005

AbstractNitrogen‐ion implantation of conventional Cr and amorphous bright chromium‐deposited (ABCD) films which were preannealed at various temperatures, has been carried out in order to determine the effect of implantation on the hardness of the Cr layers. The implantation was carried out using low ion beam fluxes in order to maintain a sample temperature below 250°C. Implantation leads to increased hardness, but the extent is most pronounced for conventional films which were not annealed and ABCD films which were annealed at or below 400°C for ½ h. The surface sensitivity of the hardness measurements was varied by altering the load used during the test. Data obtained in this manner show that the more surface‐sensitive hardness is greater than the more bulk‐sensitive hardness for both the implanted and non‐implanted ABCD films and the implanted conventional Cr films. The compositions of the implanted films have been characterized using Auger electron spectroscopy in conjunction with sputter depth profiling. These data show that all of the Cr in the implanted region is bound as CrN, Cr oxides and Cr carbides at large total N+ doses. Furthermore, the N displaces the C in ABCD films producing N and C profiles that mimic each other in an inverse manner.
SIMS analysis of InP, GaAs and InGaAs layers grown by chemical beam epitaxy
Authors: Gao Y. , Godefroy S. , Benchimol J. L. , Alaoui F. , Alexandre F. , Rao K. 
Published: May 2005

AbstractSIMS analysis was applied to the characterization of InP, GaAs and InGaAs grown by chemical beam expitaxy (CBE). It includes the control of purity and doping, and the determination of growth rate and matrix composition. Some important characteristics of CBE growth, such as carbon incorporation, the temperature dependence of the growth rate and contamination by isoelectric elements, were studied carefully.
Surface analysis of chrysophosphate materials
Authors: Berghmans P. A. , Muir I. J. , Adams F. C. 
Published: May 2005

AbstractIn this paper, we present results from SIMS, XPS and Fourier transform infrared photoacoustic spectroscopy (FTIR‐PAS) in order to determine the nature of the phosphorus compounds produced by the reaction of POCl3 gas and chrysotile asbestos. SIMS ion images show that the phosphorus compounds are evenly distributed over the surface of the chrysotile fibres (within the resolution of the Cameca ion microscope) XPS and FTIR‐PAS were used to monitor the conversion of the adsorbed POCl3 to a proposed polyphosphate coating. The formation of the polyphosphate coating occurs during the heating of the POCl3‐treated chrysotile fibres to 300°C for 2 h. The resulting material is known as chrysophosphate. This study relates to the use of chemical coating to reduce the carcinogenic behaviour of chrysotile asbestos fibres.
AES, EELS and XPS study of ion‐induced GaAs and InP(110) surface and subsurface modifications
Authors: Valeri S. , Lolli M. 
Published: May 2005

AbstractLow‐energy Ar+‐induced modifications of III–V semiconductor (110) surfaces have been investigated. XPS, angle‐resolved AES and Auger profiles have been used to check the in‐depth composition over the range of tens to hundreds of angstroms. The actual composition of the sputtered surfaces has been determined by either the elemental standard method or normalization to the cleaved surface signals. Auger and XPS lineshape analysis and EELS spectra provided information on the chemical state of the components in the sputter‐altered region.GaAs and InP surfaces have been found to be metal enriched, the enrichment being larger at high ion beam energy. The 5 keV Ar+bombardment of the cleaved InP target results in the steady‐state composition In(67)P(33) at the surface. The composition is graded in the subsurface region up to the stoichiometric value In(50)P(50). Although the sputter‐altered GaAs region can be depicted roughly as As‐depleted, the As concentration is larger at the surface than in the subsurface region. The surface ‘spike’ and the subsurface ‘dip’ in the As concentration strongly depend on the ion beam energy in terms of both the intensity and the extension in depth. These results indicate that As radiation‐enhanced Gibbsian segregation and P preferential sputtering are the dominant mechanisms of surface modification in GaAs and InP, respectively.
Determination of sputter damage on InP by MAI ellipsometry
Authors: Dinges H. W. , Kempf B. , Burkhard H. 
Published: May 2005

AbstractInP wafers were ion‐beam‐etched using different energies. The damaged surfaces were investigated by ellipsometry at different angles of incidence as a function of wavelength. Penetration depths and changes in refractive indices nD – iKD are shown. Si3N4− coated sputter‐etched InP wafers are also measured with multiple angle of incidence (MAI) ellipsometry. Coatings are removed step by step by wet chemical etching, and MAI ellipsometry is carried out after each step. The results are fitted to the model InP/sputter‐damaged layer/Si3N4. The parameters for the damaged layers are given.
Short‐range‐order investigation by low‐energy electrons
Authors: De Crescenzi M. , Derrien J. , Lozzi L. , Picozzi P. , Santucci S. 
Published: May 2005

AbstractDuring the last few years a number of experimental techniques have been developed with the general purpose of obtaining structural information from EXAFS‐like spectra without resorting to synchrotron radiation. The aim of this paper is to show the physical principles and the experimental results concerning two of these techniques, which basically use low‐kinetic‐energy electrons instead of x‐rays to excite the investigated system. EELFS (extended energy loss fine structure) and EXFAS (extended fine Auger structure) spectroscopies refer to the detection of the features that appear in the secondary electron distribution diffused inelastically from a solid surface. These features are located in energy a few hundreds of electron‐volt above a core edge ionization and above a few selected Auger transitions, respectively.The satisfactory agreement in the structural determination (position of the nearest‐neighbour distance, back‐scattering amplitude, total phase shift…) obtained by the EELFS technique allows us to conclude that the EXAFS formalism is a valid and correct method of analysis. Moreover, we present a complete calculation of the inelastic cross‐section actually measured in an EELFS spectrum, taking into account the various weights of the final‐state angular momenta. The main result of this computation ensures the predominance of the dipole channel over the other multipole contribution, even for very low primary beam energies.The interpretation of the EXFAS singal is closely related to that of the EELFS singal, both arising from an interference effect between the core excited and back‐scattered components of the final‐state wave function. Although the proposed EXAFS‐like origin awaits a more complete theoretical support, the EXFAS technique provides a very attractive extension of Auger spectroscopy to study also the local surface structure.
Take‐off angle and film thickness dependences of the attenuation length of X‐ray photoelectrons by a trajectory reversal method
Authors: Gries W. H. , Werner W. 
Published: May 2005

AbstractThe meaning of attenuation length (AL) of x‐ray photoelectrons (and Auger electrons) in solids is reviewed in the light of new evidence pointing to strong dependences of AL on take‐off angle and film thickness, which can be traced back to elastic scattering. Since signal attenuation in XPS (and AES) can deviate significantly from an exponential form, it is concluded that the AL can no longer be regarded as a material constant. Instead, the AL becomes an approximating parameter whose numerical value must be determined for each experimental condition.The take‐off angle dependence of the AL was investigated by an efficient Monte Carlo computer code, which is based on the concept of trajectory reversal; this concept is explained.Strong dependences of the AL on take‐off angle and film thickness were found for the more oblique (> 60° off‐normal) emission.