For quantitative analysis by AES and XPS, it is important to test the theory and to use the correct sensitivity factors. We develop our previous analyses of peak area intensities for elemental spectra in digital Auger and X-ray photoelectron databases measured using a fully calibrated spectrometer. The intensities, instead of being analysed after removal of a Tougaard background are now analysed after removal of the extrinsic characteristic loss background by deconvolving the elemental angle-averaged reflected electron energy loss spectrum (REELS). The photoelectron spectra now show clear intrinsic shake-up intensities, reduced to around 30% of the total peak intensities. A comparison of theory and experiment within a new matrix-less quantification formulation, using average matrix sensitivity factors, leads to correlations with rms scatters of 8% and 11% for AES and XPS, respectively, for a very wide range of transitions. This gives formulae and values of sensitivity factors, appropriate for use with spectrometers calibrated to give true spectra.

View full abstract

Inelastic mean free paths of electrons were determined from QUASES spectral shape analysis of high energy photoinduced K-Auger spectra of Cu, Ni and Co thin films, as well as of Fe K-conversion spectra attenuated by Au overlayers of various thicknesses. The results found from analysis of spectra from different layer thicknesses are consistent and they are compared with available estimations in the literature.

View full abstract

We have determined inelastic mean free paths (IMFPs) in silver, gold, copper, and silicon in the 50-5000 eV energy range from electron elastic peak intensity ratios to a nickel reference material, and Monte Carlo simulations. The resulting IMFPs were analyzed using Fano plots, and those values for silver, gold and copper could be fitted by the Bethe equation in the 50-5000 eV energy range. The resulting IMFPs for Ag, Au, Cu, and Si are in excellent agreement with IMFPs calculated from the Penn algorithm or the TPP-2M equation in the 200-5000 eV energy range.

View full abstract

Automatic background estimation for XPS, AES and EDX spectra is attempted in order to make rapid qualitative and/or quantitative analyses. The start and end points of the background at both sides of each spectrum peak are obtained on a given algorithm. To link these start and end points, the background curve can be chosen from two methods: linear or Shirley. The selection of the methods gives not a negligible difference on the result of the quantitative analysis for a spectrum with high background.

View full abstract

Recent development of background optimization is described. Assumed peak intensities and boundaries for integration that were fixed in the former version can be treated as optimization parameters. The ‘effective’ loss function is allowed to take negative value to analyze non-uniform material. In addition to peak ratio and tail intensity, peak intensity is treated as a new optimized functional. The Al XPS spectrum is analyzed.

View full abstract

Efforts for restoration of the loss function from the XPS spectra of relatively poor resolution have been in progress. A new objective function and improving algorithm have given better convergence than reported before.

View full abstract

One of the fundamental parameters in quantification of sputter depth profiles is the sputtered depth. Usually, the sputtered depth is not known from the measured profile, because only the sputtering time is recorded. Only if the instantaneous sputtering rate (=sputtered depth per unit of time) is known, the depth scale can be derived from the time scale. To determine the average sputtering rate, a certain sputtered depth has to be correlated with a measured sputtering time. In general, the sputtered depth has to be determined by additional measurements that is the topic of a recently published ISO Technical Report (ISO/TR15969). In this work, we focus on the correction of the time scale in terms of a true depth scale in case of preferential sputtering of one component of a binary system with concentration variation, as shown for the example of a Si/Ta multilayer. Using a modified version of the MRI model, it is shown how the correct the time/depth relation for quantification of sputter depth profiles is obtained.

View full abstract

We have analyzed the interfaces in Auger depth profiles, for the Ni/Cr multilayer specimen and the GaAs/AlAs superlattice specimen, using curve fitting process by the logistic function. In consequence, the calculated fitted profile curves are in very good agreement with the measured points. Moreover, it has been found that the depth resolution function is expressed by two parameters of the interface-width and the asymmetry. In this report, we recommend that the surface roughening effect and atomic mixing effect are clearly shown using these two parameters. It is shown that the roughening parameter D₀ in the logistic function also well correlate with the roughness parameter in the MRI model.

View full abstract

This paper reports on the application of SOM to chemical spectra analysis. The Self-Organising Map (SOM) method that was developed by T. Kohonen [1] was first applied to information processing. Currently, it has been applied to some problems of chemical spectra analysis using AES (Auger Electron Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), and XRD (X-ray Diffraction) data. Using a 2-dimensional SOM, it became clear that the items that are described qualitatively by linguistic expressions could be explained more quantitatively by the position of the spectral data on the SOM together with a grey level expression. Also, the composition of an unknown sample can be determined very precisely by the SOM that has been constructed using the spectra from samples of known composition. Furthermore, this paper addresses the attempts to develop a SOM of all the elements of the periodic table. Currently, only 77 elements have been mapped out.

View full abstract

The NIST Electron Effective-Attenuation-Length Database provides values of electron effective attenuation lengths (EALs) in solid elements and compounds at selected electron energies between 50 eV and 2, 000 eV. The database was designed mainly to provide EALs (to account for effects of elastic-electron scattering) for applications in surface analysis by Auger-electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). For these applications, EALs are needed mainly for measurements of the thicknesses of overlayer films and to a much lesser extent for measurements of the depths of thin marker layers. EALs are calculated using an algorithm based on electron transport theory for measurement conditions specified by the user. The database also provides values of other parameters needed for other quantitative applications of AES and XPS.

View full abstract

One of the wide band gap III-V compound semiconductor, GaN, is expected to be utilized for the high-functional optical device due to its superior chemical-stability. In the present study, it has been investigated what is the most important factor determining the position of the Fermi level at the interface between GaN and depositing metal through studying interfacial electrical properties, bonding state and thermal stability. Under ultrahigh vacuum, Ni, Pd, Pt, Au, Ti, Cr and Al were in-situ deposited on both types of GaN grown by MOCVD and studied by photoemission, AES depth profiles and AFM. Through the band bending analysis, it can be recognized that unless the new layers, like either TiN or CrGaN, are not formed, the band bending depends more upon the solid state electronegativity than the work function of the contacting metal. Most of metals were uniformly deposited, and especially Ti, Cr, and Al were reacting with GaN at the depositing instant resulting in the novel phase mixing with N and Ga segregation. On the other hand Ni, Pd, and Pt did not form any nitride and their on-set temperature for reacting with GaN were different (T_Ni<T_Pd<T_Pt).

View full abstract

Laboratory XPS imaging has changed dramatically with the most recent generation of XPS instrumentation. Image acquisition times of seconds to minutes have transformed XPS imaging from a novelty to a routine analysis method. This transition has been facilitated by the development of focused x-ray sources, new analyzers and improved detection systems. Methods of image acquisition, and current capabilities will be demonstrated, and speculations about future developments will be offered. This enhanced surface chemical characterization of heterogeneous samples comes at the cost of increasing complexity in the XPS data sets acquired. For example, in a spectra-from-images experiment, images are acquired as a function of binding energy. The resulting multi-spectral imaging data set is a complex data structure, requiring more sophisticated analysis methods than visual inspection, if the data are to be interpreted effectively. We will discuss a variety of multivariate analysis methods that can be utilized to assist in the evaluation of large data sets New opportunities for multi-technique correlations also arise from the improved spatial resolution and decreased data acquisition times. A variety of techniques, including FTIR, AFM and TOF-SIMS have spatial resolutions comparable to, or better than XPS, making correlative analyses possible. Examples demonstrating the additional information obtained when XPS measurements are combined with imaging FTIR or AFM will be shown. Considerations in comparison of images of very different spatial resolutions will be discussed.

View full abstract

Grazing Incidence X-ray Photoelectron Spectroscopy (GIXPS) is a method that offers promise as a nondestructive technique to measure the thickness and chemistry of ultrathin gate dielectric films. It combines aspects of x-ray reflectivity and conventional x-ray photoelectron spectroscopy (XPS). Collimated x-rays are incident on the sample at a grazing angle. A series of photoemission spectra are obtained over a range of incidence angles in the vicinity of the critical angle for total external reflection. The advantage of this method is the incorporation of the optical constants of the layers, as well as the photoemission cross sections of the elements and the inelastic attenuation lengths of the escaping photoelectrons, to fit the nonlinear variation of the photoemission spectra as a function of angle. The x-ray field variation with angle within individual layers provides additional constraints beyond standard angle-resolved XPS for interpreting the densities and thicknesses of multiple layers. The application of this method to the analysis of oxide on Si is described.

View full abstract

The relative work function of growing surface of molecular epitaxy films was measured in situ using the energy shifts observed in secondary electrons excited by reflection high energy electron diffraction beam. In the case of a superconducting perovskite YBa₂Cu₃O_x the measured work function showed different behaviors between the coevaporation and the sequential evaporation of the metal elements reflecting differences in the electronic structures of the growing surfaces.

View full abstract

An iteration method in the energy calibration of AES has been developed by using elastically backscattered primary electrons with possibility of 15 meV (σ) for the energy range from 10 eV to 1200 eV, in which our improved novel prototype cylindrical mirror analyzer (CMA) has been used. For the true kinetic energy calibration, the relative work function of sample to CMA was investigated by changing sample bias to CMA at ground level. It can be obtained by observing the onset of secondary electrons (SE) since SE are believed to begin just above “0” of vacuum level, although it is hardly possible to obtain a true spectrum.

View full abstract

The ion beam stability is important for achieving reproducible depth profiles. This report describes how the ion beam position shift occurs after turning on the filament, and how this shift affects the results of depth profiling. It was found that the largest shift was more than 200 nm along the y-direction even when the inclined sample holder was used. It requires more than 5 hours to stabilize the ion beam position in our instrument. Immediately after turning on the filament the sputtering rate of SiO₂ was 10% smaller than the rate measured after stabilization. However, the depth resolutions were almost the same in both cases. It is advisable to check the stability of the ion beam position before measuring the sputtering rate precisely.

View full abstract

We propose a novel surface analysis method, “X-ray traveling waves using an X-ray waveguide”. The traveling wave is an opposite concept of the standing wave. The X-ray standing waves have been used for the analysis of surfaces by total reflection X-rays. The traveling wave is the X-rays refracted at the surface, and this novel method is to detect the refracted waves at the cross-section of a specimen. Such a traveling wave shows strange features, the origins of which are still not clarified, but also shows a similarity to the “Yoneda wing” phenomena.

View full abstract

We have demonstrated the potentials of a field emission scanning tunneling microscope (FE-STM), in which the STM tip can be operated as a stable field electron emission gun. The tips were treated by a thermal-field (T-F) method for remolding and cleaning. A well-controlled T-F treated tip can determine the electric field between tip and sample in the STM as a geometrical boundary condition. Using the treated tip the electron standing waves excited in a vacuum gap between tip and sample were analyzed, and the electric field near sample surfaces was evaluated by assuming a simple potential model. Furthermore, by irradiating sample surfaces with a high-energy electron beam emitted from the tip, we obtained electron energy loss spectra (EELS) and Auger electron spectra from semiconductors, HOPG and metals.

View full abstract

Single electron charging effects were observed for gold nanoclusters grown on octanedithiol self-assembled monolayers by scanning tunneling microscopy and X-ray photoelectron spectroscopy. Strong interaction of gold with the terminal sulfur atoms of dithiol molecules on Au(111) suppresses effectively the penetration of deposited Au atoms through the dithiol layer and results in the formation of homogeneous Au nanoclusters. Decoupling of the clusters from Au(111) by the octanedithiol layer and the small self-capacitance of the nanoparticles realize the observation the Coulomb blockade in scanning tunneling spectroscopy and the Au 4f core level shifts in X-ray photoelectron spectroscopy at room temperature. Both phenomena origin from a common physics, the Coulomb energy of charged particles.

View full abstract

In order to analyze the trace metals at the level of 10⁸−10⁹ atoms/cm² on the silicon wafers, it is important to control the analytical environment, water and chemicals, and to clean and to handle carefully the analytical equipments and implements. These notes lead to decrease the contamination in the original acid solution that is used to collect metals in it. Some metals slightly contaminated in the original acid solution analyzed by ICP-MS for about three years were controlled within the range of 1-25 wt·ppt in our experiments. The detection limits of each metal for 8-inch silicon wafers are 3×10⁸ −1×10⁹ atoms/cm². The intensity analyzed by ICP-MS for each metal tended to decrease to 80% with increasing the concentration of Si matrix more than 50 wt·ppm, while that by GF-AAS recorded virtually the same. The recovery rates for each metal except Cu were at least 95% for original concentration levels of 10¹⁰-10¹² atoms/cm². The recovery rate of Cu was 80-90%.

View full abstract

The 3rd generation synchrotron radiation (SR) facilities have been recently built and have given us high flux and wide-energy tunable X-ray. This characteristic is useful to obtain XPS spectra excited by the high energy X-ray, which reveals the deeper layers. In this work, we used the beamline of SPring-8 BL15XU which has an revolver type undulator and a double crystal tandem monochromator and the angle-resolved XPS machine where an energy resolution is good even if X-ray energy is high up to 4500eV. For multilayers of the magnetic tunnel junction device, XPS measurement using 3000eV X-ray led to evaluate the deeper layers of a specimen and revealed the interface between Al oxide and Fe₅₀Co₅₀ alloy with Ta oxide or carbon protective overlayers.

View full abstract

Surface and interface phenomena play important roles in many properties of iron and steel. For instance, the surface of plain carbon steel is easily corroded in air with humidity. In order to improve the surface properties of steel, various kinds of coatings have been developed. Surface analytical techniques are used for characterizing the coatings and surface layers on steel. Typically, glow discharge optical emission spectrometry (GD-OES) is often used for rapidly evaluating the composition and thickness of the coatings. XPS, AES and SIMS are also applied to characterization of thin layers formed on the surface and interface of steel. These techniques provide essential information on enrichment of elements such as the surface segregation and grain boundary segregation. However, systematic experiments have shown that analyzed results are affected by microstructures of iron and steel. Therefore, the surface and interface phenomena should sometimes be investigated by different methods and from different viewpoints, in order to understand all the features of the phenomena. The present paper gives analyzed examples of these surface and interface phenomena analyzed by the surface analytical techniques and other techniques.

View full abstract

GD-OES has been used for characterizing the behavior of nickel during oxidation in Fe-Ni alloys. GD-OES depth profiles show that nickel is enriched at the interface between the oxide layer and matrix, and nickel is almost depleted in the oxide layer. Based on the relationship between the amount of nickel and the oxide thickness, characteristic features of nickel in the oxidation of Fe-Ni alloys is discussed.

View full abstract

SIMS and XPS have been applied to characterize the elemental distribution in the internal oxidation zone of an Fe-6mol% Si alloy. Internal oxidation behavior agrees well with predictions based on the thermodynamic data of oxidation. Redistribution of trace elements is deeply related to internal oxidation and interface segregation.

View full abstract

Surface segregation of Al in the Cr/Al/Al thin film system was observed at 813K. The film was deposited by rf magnetron sputtering. The segregation phenomenon and the depth profile of the segregated layer were monitored by XPS. Cr 2p and Al 2s photoelectron peaks were analyzed in detail to investigate the chemical interaction of the segregated layer (Al) with the film material (Cr).

View full abstract

Understanding the surface and interface structure, composition and chemistry of insulating materials has long been of importance in surface analysis. The relevance of insulating surfaces to the environment, and the increasing use of newer and more complex oxide films in electronic and optical applications significantly increases the information needed about these materials. Through a series of examples using Al-oxide films, this paper summarizes some conceptual and practical issues related to analysis of insulators, including vacuum-level and Fermi-level referencing, charge buildup at interfaces, the use of charge neutralization, the impact of electron and ion-beam damage, and the influence of impurities on oxide properties and measurements. Many of the measurements are understood through consideration of potential variation through a specimen. Current results, along with many in the literature, demonstrate that surface charging is not a problem that can be readily solved and ignored, but is a tool providing important information about materials and films.

View full abstract

Surface analytical investigation with AES and XPS has been performed on Cu-Ni multilayer and its impact compressed sample. A well formed Cu-Ni multilayer using RF magnetron sputtering system with MMPC has been observed. The possibility of the formation of a Cu-Ni alloy after the high speed impact compression has been found, and this suggests that the impact compression method is useful for the preparation of metal alloys.

View full abstract

Redistribution behavior of B and O during silicidation process of titanium-silicon system at 923 K has been examined by secondary ion mass spectrometry and transmission electron microscopy. Amorphous like TiSix forms between unreacted Ti and TiSi₂. B accumulates in TiSix and O accumulates in unreacted Ti. The solubility of B and O in Ti and TiSix causes the difference of redistribution behavior of B and O during Ti silicidation.

View full abstract

Solder composition was evaluated with several methods of surface analysis. Since solder is a heterogeneous alloy, ordinary surface analysis is not adequate for accurate determination of its composition. Recently however, a method of quantification with phase analysis has been introduced in EPMA for heterogeneous systems. In this paper, we examine the validity of phase analysis for Sn-Pb eutectic solder and Sn-3.0wt%Ag-0.5wt%Cu solder, and found that phase size needs to be considered when using phase analysis.

View full abstract

The validity of the application of angle lapping method of investigation of the microstructure between the Sn-3.5wt%Ag-0.75wt%Cu Pb-free solder and substrate has been tried. Some of interface layers were too narrow to analyze the microstructure even using TEM of standard cross sectional analysis. But angle lapping method enabled showing elemental mapping by EPMA because of the apparent width was a few micrometer whose original width was less than 0.1 μm. The reaction layer formed between Sn-3.5wt%Ag-0.75wt%Cu and Ni-electroless plate was divided two phases composed void rich layer of (Ag, Cu)-Sn phase and another one was Sn-Cu phase. The component analysis of both layer could not be delected by the standard cross sectional analysis. This results indicated that angle lapping method is powerful for the thin area analysis.

View full abstract

The wettability of Sn-Cu and Sn-Pb solder platings accelerated by pressure cooker test and high temperature shelf test was evaluated through meniscograph and the platings were surface analyzed through XPS, SEM and EDX for the determination of main factors to reduce the wettability. The surface of Sn-Cu platings has a stable oxide layer, SnO₂, which is thicker for the samples kept in higher humidity atmosphere. Wettability of Sn-Cu platings does not decrease even in high temperature atmosphere, but that of thin (1μm) Sn-Pb platings reduced. Both of Sn-Cu and Sn-Pb platings do not show remarkable change in the wettability by the component of solder bath. It is suggested that the diffused Cu atoms from the brass substrate and Ni atoms from the plating under the solder plating does not effectively obstruct the wettability. Thus, the main factor for wettability reduction is concluded to be the surface oxide layer and its thickness.

View full abstract

High dielectric constant materials have received much attention for use as gate dielectric films and capacitor dielectric films of advanced devices. We plan to use Ta₂O₅ for capacitor dielectric films and Ru or RuO₂ for both top and bottom electrodes because Ta₂O₅/Ru (RuO₂) show excellent performance with the dielectric constant rising to about 70, i.e. an SiO₂-equivalent thickness of 0.7nm at a Ta₂O₅ thichness of 10nm. [1] We have adopted XPS (X-ray photoelectron spectroscopy) for one part of the capacitor evaluation. XPS is used not only for analysis of components and chemical states but also to depict the energy-band diagram from fine structure of the spectrum. This paper discusses part of our evaluation techniques for using XPS to study capacitor materials of advanced memory devices.

View full abstract

Interdiffusion at the interfaces of a multilayer structure consisting of 3 Ge layers of about 2.2, 4.3 and 2.2 nm thickness in a Si matrix was studied by depth profiling with AES. Measured depth profiles of the as deposited structure (grown at 300°C), taking the Ge LMM peak intensity as a function of the sputtering time, were compared with those obtained after annealing of the sample at 600, 650, and 700°C after quantitative evaluation with the MRI (mixing-roughness-information depth)-model. As a result, the interdiffusion constant was determined (D_eff=6.3 E-22 m²/s at 973 K) as well as the activation energy (E≅0.9 eV). These values are considerably lower than the bulk diffusion coefficients. This effect presumably is connected with the strain in thin film multilayer Si/Ge heterostructures due to the lattice mismatch. It is especially important at low temperature annealing and has to be taken into account in the fabrication technology of of Si/Ge nanostructures.

View full abstract

We investigated the natures of chemical bond at silicide/silicon interfaces for four silicide films (CoSi₂, NiSi₂, TiSi₂ and WSi) using X-ray photoelectron spectroscopy (XPS), with the purpose of getting insight on the nature of silicide/silicon interface. In the case of CoSi₂ and NiSi₂, the difference between XPS binding energy of metal and silicon peaks increased at silicide/silicon interfaces, whereas the difference for TiSi₂ and WSi decreased. The XPS binding energy differences between metal and silicon peaks before and after interfaces had good correlation with work function of metal, and relevance to Schottky barrier height at interface.

View full abstract

It was shown that MEIS can provide reliable thickness measurement of nm gate oxides down to 1∼2 nm range with additional interface strain profiles which show interesting correlations with electrical properties. Its absolute quantification capability with atomic layer depth resolution can be utilized to develop delta doped reference thin films especially for SIMS shallow junction profiling. It was discussed that MEIS has quite high potential to contribute to the further development of nm ultrathin films with atomic resolution to meet the challenging and urgent demands from nano-electronics technology.

View full abstract

We propose the Same Surface Contact Method (SSCM) that is useful to protect the surface of a specimen against contamination and oxidation in the air. The contamination and the oxidization of the surfaces of Fe-Si-Al films were investigated by X-ray photoelectron spectroscopy (XPS). Surface oxidation gradually proceeded in the air, while the increase in surface contamination was restrained for a long time in the air by SSCM. It was also found that the surfaces could be protected against oxidization in the nitrogen atmosphere.

View full abstract

The aim of this work was to get a better understanding of the O 1s binding energies E_b(O1s) in complex glasses of interest in nuclear waste storage in relationship with the mean charge on the oxygen atoms, relevant to acidic/basic properties of the glass. Three different glasses were considered: an aluminum borosilicate, a lanthanum aluminosilicate and a calcium aluminosilicate. The O1s binding energies were measured for each glass, along with individual simple oxides. The oxygen charges were estimated by an empirical method based on the electronegativity equalization principle. We show that for the first two glasses, the O 1s binding energy shift is driven by the changes in the oxygen charge induced by mixing the oxides to obtain the glass For the latter glass however, Madelung effects are of prime importance and the E_b(O1s) value of the glass cannot be predicted from the values in the individual oxides.

View full abstract

In this study, we examined Ar⁺ ion sputter etching rate ratio R_Al203/R_SiO2 under different surface charging conditions and in different incident azimuthal directions of Ar⁺ ion. When the surface charging of specimen was neutralized by irradiation with low-energy electrons, R_Al2O3 became larger than that of specimens without any electron irradiation at same ion current density. When the specimen was bombarded by Ar⁺ ion from the azimuthal direction parallel to the a-axis on the surface of Al₂O₃ single crystal, R_Al2O3/R_SiO2 became higher than that of specimen bombarded from the azimuthal direction vertical to the a-axis. The effects of surface charging and incident azimuthal direction of Ar⁺ ion on R_Al2O3/R_SiO2 are discussed respectively on the basis of the experimental results.

View full abstract

XPS has been used for investigating the influence of argon ion sputtering on the chemical state and composition of the surface of three iron oxides, Fe₂O₃, Fe₂NiO₄ and Fe₂ZnO₄. XPS spectra of these oxides were measured, while bombardment by argon ions of 3keV were interrupted. The chemical state of the surface of these oxides was found to change from Fe³⁺ to Fe²⁺ by argon ion bombardment, suggesting the reduction of the surface of these oxides. This behavior was attributed to a decrease of the oxygen composition of the surface of these oxides. Then, particular attention should be paid in analysis of a layered structure of oxides formed on the iron and steel surface.

View full abstract

Angle resolved XPS measurements were performed for a reduced TiO₂ single crystal after Ar ion sputtering with 500 V in order to examine the depth profile of the reduced states. Comparing this angle resolved XPS measurement with the calculation, the component of Ti²⁺ has a gaussian like depth distribution. The component of Ti³⁺ is a localized near surface and smoothly distributed inner layer. Ar ion bombardment with low angle incidence was performed in order to decrease the thickness of the reduced layer. The intensities of the reduced states decreased with lowering incident angle of Ar ion. Moreover, ion bombardment with the low angle incidence has revealed that most of the reduced states are decreased and the intensities of the undamaged Ti⁴⁺ components are increased. These results prove that suitable conditions for the Ar ion sputtering will give a correct depth profile of the chemical states for the compounds which are altered by the ion bombardment.

View full abstract

We have studied the electronic structures of Al/MgF₂/tris-(8-hydroxyquinoline)aluminum (Alq₃) interface using UV and X-ray photoelectron spectroscopy (UPS & XPS). The UPS revealed that the valence peak shift occurred with MgF₂ deposition before Al was deposited and was independent of the gap state formation. The XPS core level peaks indicated that the MgF₂ strongly interacted with Al and O atoms in Alq₃ even before Al was deposited, and the deposition of Al caused slight change to the N 1s core level peak. These results indicate that the interaction mechanism in Al/MgF₂/Alq₃ is different from those found in Al/LiF/Alq₃ and other metal/Alq₃.

View full abstract

We propose a new approach for analysis of Auger electron spectra (AES) of polymers by density functional theory (DFT) calculations with the Slater’s transition state concept. Simulated AES and X-ray photoelectron spectra (XPS) of three polymers (PE, PcBD, and PS) by our DFT calculations using model dimers are in good accordance with the experimental ones. The combined analysis of AES and XPS can help us to clarify the electronic structure of polymers from the theoretical viewpoint.

View full abstract

We examined surface damage for polyvinyl chloride (PVC) sample after 260 minutes at an unmonochromated Al Kα X-ray source power at 600 W, because PVC decomposes very quickly due to the X-ray irradiation. The pendant Cl groups of the PVC were estimated to cleave more rapidly than C-C bonds in the main chains from two-center bond energies calculated by AM1 method using the model pentamer. The valence XPS of the polymer at the initial time, and after 120 and 260 minutes of X-ray irradiation were analyzed by deMon density-functional theory (DFT) calculations using the model pentamer. The simulated results afforded us that the pendant Cl groups of PVC cleave mainly due to the X-ray radiation.

View full abstract

X-ray photoelectron, and Auger electron spectra of diamond, graphite, and C₆₀ fullerene have been analyzed by deMon density-functional theory (DFT) calculations using the model adamantane derivative (C₁₀H₁₂(CH₃)₄), pyrene (C₁₆H₁₀), and C₆₀ molecules, respectively. The theoretical valence photoelectron, and Auger electron spectra for the allotrope show good accordance with the experimental ones, although we couldn’t also observe the Auger electron spectrum for solid C₆₀. The experimental AES of the allotrope can be classified in each range of 1s-2p2p, 1s-2s2p, and 1s-2s2s transitions for C KVV spectra.

View full abstract