Photoelectron angular distributions of Cu,Ag, Pt and Au samples: experiments and simulations

Angular distributions of photoelectrons emitted from semi‐infinite Cu, Ag, Pt and Au specimens have been measured for off‐normal emission angles in the range between 20 and 70° with a Thermo Theta Probe electron spectrometer. Experimental peak intensities for peaks of atomic subshells observable in the spectra were compared with results of simulations using the NIST Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) that takes into account the effects of (i) anisotropy of the photoelectric cross‐section; (ii) elastic scattering of the photoelectrons; and (iii) the finite solid angle of the detector. In addition, a separate correction was made to the simulated intensities for the effects of surface excitations. The combined influence of these effects was found to significantly affect the angular distributions. Furthermore, it was found that ratios of the calculated peak intensities of the observed subshells for a particular material to the measured intensities deviate from unity by typically less than 1% after corrections for multiple inelastic scattering and surface excitations. Copyright © 2010 John Wiley & Sons, Ltd.     

Highly angular resolved x‐ray photoelectron diffraction measurements from a Ge(111) surface

Using a high angle‐resolving electron energy analyser with a novel input lens system, we measured Ge 3p x‐ray photoelectron diffraction (XPED) patterns from a Ge(111) surface excited by Al Kα with changing angular resolution from ±0.04° to ±2°, and considered the angular resolution dependence of XPED patterns from experiments and theory. Highly angular resolved XPED patterns containing fine features such as Kikuchi‐like bands were obtained. These patterns were reproduced by theoretical calculations. We also performed the theoretical calculations for further investigation of highly angular resolved XPED. Copyright © 2004 John Wiley & Sons, Ltd.     

Effects of raster angle on the mechanical properties of PLA and Al/PLA composite part produced by fused deposition modeling

This paper studies the mechanical properties of polylactic acid (PLA) and aluminum fiber–reinforced PLA composite (Al/PLA) specimens fabricated by fused deposition modeling (FDM) process. The effect of raster angle (0°, 90°, 45°, 0°/90°, and ± 45°) on dynamic mechanical thermal property and tensile property of FDM‐printed PLA and Al/PLA has been studied. The results show reduced tensile strength and Young's modulus in Al/PLA composite specimen in comparison with pure PLA specimen. However, the elongation‐at‐break increases, which is due to Al fiber with the higher elasticity and lower tensile strength than PLA. The addition of Al fibers improves the dynamic mechanical thermal property of pure PLA because of the good interaction of the PLA matrix with the surrounding Al fibers. Raster angle plays an important role in FDM process. All specimens printed with 0° raster angle show highest tensile strength and dynamic mechanical properties, while specimens printed with 90° raster angle have the lowest values. Fractured surfaces indicate that the failure of the specimen with 0° raster angle is due to breaking of individual layers, while for 90° raster angle, specimen fails under separation of the adjacent raster layers.     

Magnetic moment distributions in α- Fe nanowire array

α-Fe nanowire array has been electrodeposited into anodic aluminum oxide template. The magnetic moment distributions, in the interior and near the extremities of α-Fe nanowire with 60 nm in diameter, have been studied by means of transmission Mössbauer spectroscopy (MS), conversion electron Mössbauer spectroscopy (CEMS) and micromagnetic simulation. Transmission Mössbauer spectrum (MS) shows that the magnetic moments, inside the α-Fe nanowire array, are well parallel to nanowire, while conversion electron Mössbauer spectrum (CEMS) reveals that the magnetic moments, near the extremities of nanowire, diverge from the long axis of wire, and the average diverging angle calculated by the intensity ratio of the 2,5 peaks is about 24.0°. Moreover, the magnetic moment distributions of different depths to the top of wire are counted using micromagnetic simulation, which indicates that, the interior magnetic moments are strictly parallel to nanowire, and the closer the magnetic moment to the top of wire, the larger the diverging angle. Magnetic measurement shows that this α-Fe nanowire array represents a strong magnetic anisotropy.     

Effect of AlSiFe on the anodizing process of 6063 aluminum

AlSiFe phase can form microscopic galvanic couples that decrease corrosion resistance of 6063 aluminum which may influence the anodizing process. Two samples of 6063 aluminum were prepared. One sample was cut along the extrusion direction of the billet, and the other was cut perpendicular to the extrusion direction. Both samples exhibited the same characteristics, except for the distribution of the second phase AlSiFe. Both samples were subjected to anodizing treatments. Comparison between anodic oxide films was performed. The microstructure of Al substrates and anodic oxide films were examined using a scanning electron microscope, an optical microscope, and a glow discharge optical emission spectrometer. Results indicated that the thicknesses and elemental distributions of the anodic oxide films were almost the same. Moreover, the second phase AlSiFe influenced the anodic oxidation process, resulting in cavities in the anodic oxide film that affected its brightness. Copyright © 2016 John Wiley & Sons, Ltd.     

Ultrathin SiO2 on Si. VII. Angular accuracy in XPS and an accurate attenuation length

Following an earlier study of the uncertainties for defining thicknesses by angle‐resolved XPS, one of the major instrumental uncertainties has been evaluated that limits both precision and accuracy. For analysis of the thicknesses of SiO₂ on Si, certain angles of emission have been recommended, but an error of 1° in these angles leads directly to an error in the thickness of ～1% from this contribution alone. This is significant since the total uncertainty required in the (International technology roadmap for semiconductors) ITRS is only 1%. In many instruments, to reduce sample‐stage vibration and for other reasons, the angle and other setting adjustments are engineered with backlash. This, combined with the manufacturer's tolerances, can lead to angular errors above 1°. We report here a device using a laser and reflectors, fixed to the sample mount, that allow the angle of emission to be set to a precision better than 0.1° and, furthermore, a method to set the zero angle of emission to 0.1°. Using this geometrical device as well as by measurements of intensities in XPS, it is deduced that the data in our earlier report for the CCQM (Consultative Committee for Amount of Substance) intercomparison were for angles 1.89° ± 0.15° too high. Consequently, by a re‐analysis of all of that data, we find that our recommended attenuation length data for the Si 2p photoelectrons in thermal SiO₂ using Mg or Al Kα X‐rays should be increased to 2.996 nm and 3.485 nm, respectively, an increase of 1.2% on the originally calculated values. These values now have standard uncertainties of 0.54% instead of the 20% of the TPP‐2M calculations. This leads to an improved accuracy in the measurement of ultrathin thermal oxides on silicon by XPS, of better than 1% for thicknesses greater than 1.5 nm but less than 8 nm. © Crown copyright 2005. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd.     

Summary of ISO/TC 201 Standard: ISO 14701:2011 – Surface chemical analysis – X‐ray photoelectron spectroscopy—measurement of silicon oxide thickness

This International Standard specifies several methods for measuring the oxide thickness at the surfaces of (100) and (111) silicon wafers as an equivalent thickness of silicon dioxide when measured using X‐ray photoelectron spectroscopy. It is only applicable to flat, polished samples and for instruments that incorporate an Al or Mg X‐ray source, a sample stage that permits defined photoelectron emission angles and a spectrometer with an input lens that may be restricted to less than a 6° cone semiangle. For thermal oxides in the range 1‐ to 8‐nm thickness, using the best method described in this International Standard, uncertainties at a 95% confidence level around 2% may be typical and around 1% at optimum. A simpler method is also given with slightly poorer, but often adequate, uncertainties. Copyright © 2012 Crown copyright.     

Some experiments on γ-scattering between 122 and 145 keV at small angles

Differential cross section for scattering of 145.4 keV gamma rays by B, C, Al, Cu and Cd have been measured from 5–25°. For angles <10° it was not possible to separate Rayleigh and Compton scattering; therefore, the sum of the cross sections is given. Rayleigh cross sections have been measured for Pb at 122.1 and 136.5 keV at angles between 20° and 70°. The experimental results are compared with the form factor theory for Rayleigh scattering and the incoherent scattering factor theory for Compton scattering.     

Biomimetic superhydrophobic UHMWPE/nanosilica films with different sticky behavior on several metals

A kind of organic–inorganic composite film with biomimetic superhydrophobic performance was prepared on several metals including steel, aluminum, and copper. The organic matrix was ultrahigh‐molecular‐weight polyethylene (UHMWPE), and the inorganic filler was nanosilica. Scanning electron microscope observation indicated addition of nanosilica greatly changed the topography of the UHMWPE film. Special convexities were formed on the surfaces of the composite films, which made the composite films rougher than that of pure UHMWPE film. The nanosilica randomly scattered on the surface of the convexities and formed hierarchical structure similar to that of some plant leaves with superhydrophobic characteristics. Interestingly, it was found that there were remarkable differences between the sliding angles (SA) of water droplet on the composite films on different metals although the contact angles (CA) of water droplet on these films were quite close. The CA on the composite films on steel was about 157°, and the SA was larger than 90°, which demonstrated obvious superhydrophobic and sticky characteristic. But to the films on aluminum and copper, the CAs on them were larger than 160° and the SAs were between 3° and 4°, which meant excellent superhydrophobic and roll‐off performance. Scanning electron microscope observation indicated that there were some micro‐orifices in the film on steel and these micro‐orifices were connected to some extent. It was believed that these micro‐orifices provided capillary force and restrained sliding of water droplet. A sticky model based on capillary mechanism was proposed. Copyright © 2017 John Wiley & Sons, Ltd.     

Cathodic electrochemiluminescence at double barrier Al/Al2O3/Al/Al2O3 tunnel emission electrodes

Double insulating barrier tunnel emission electrodes were fabricated by adding a new pure aluminum layer upon oxidized aluminum electrodes by vacuum evaporation and thermally oxidizing the new aluminum layer in air at room temperature. Resulting Al/Al₂O₃/Al/Al₂O₃ electrodes allow the use of various aluminum alloys in the electrode body necessary for hardness or shaping ability of the electrode while obtaining the luminescence properties of pure aluminum oxide. During electrical excitation of luminescent labels by cathodic hot electron injection into aqueous electrolyte solution, the background noise is mainly based on high-field-induced solid-state electroluminescence and F-center luminescence of the outer aluminum oxide film. The more defect states and/or impurity centers the outer oxide film contains, the higher is the background emission intensity. The present electrode fabrication method provides a considerable improvement in signal-to-noise ratio for time-resolved electrochemiluminescence (TR-ECL) measurements when the original native oxide film of the electrode body contains luminescence centers displaying long-lived luminescence. The excellent performance of the present electrodes is demonstrated by extremely low-level detection of Tb(III) chelates, luminol, Pt(II) coproporphyrin and Tb(III) labels in an immunometric immunoassay by time-resolved electrochemiluminescence.     

Measurement of exchange and spin-orbit effects and their interference in elastic e-Cs scattering at 7 eV

Twenty years ago a theoretical analysis showed that electron scattering by high-Z one-electron atoms might lead to interference of exchange and spin-orbit interactions at low electron energies, observable as a cross-section asymmetry if unpolarized electrons are scattered by polarized cesium atoms. By using a highly polarized cesium atomic beam, we studied exchange and spin-orbit effects at different electron energies, starting at 20 eV and going down. We observed the first distinctly non-zero interference asymmetry at 7 eV: Over the angular range of 35 to 145°, it varies between +0.02 and ?0.02 and goes through zero near 110° being negative at larger angles.     

Monte‐Carlo simulation of x‐ray photoelectron emission from silver

Silver 3d x‐ray photoelectron spectroscopy (XPS) spectra were simulated with the Monte‐Carlo method using an effective energy‐loss function that was derived from a reflected electron energy‐loss spectroscopy (REELS) analysis based on an extended Landau approach. After confirming that Monte‐Carlo simulation based on the use of the effective energy‐loss function can successfully describe the experimental REELS spectrum and Ag 3d XPS spectrum, we applied Monte‐Carlo simulation to predict the angular distribution of Ag 3d x‐ray photoelectrons for different x‐ray incidence angles and different photoelectron take‐off angles. The experimental photoelectron emission microscope that we are constructing was confirmed as being close to the optimum configuration, in which the x‐ray incident angle as measured from the surface normal direction is 74° and the photoelectron take‐off angle is set normal to the surface. The depth distribution functions of the Ag 3d X‐ray photoelectrons for different energy windows suggest that the photoelectron emission microscope will exhibit greater surface sensitivity for narrower photoelectron energy windows. Copyright © 2003 John Wiley & Sons, Ltd.     

The formation mechanism and distribution of micro-aluminum oxide layer

It is of great significance to study the thermal oxidation process to understand the reaction mechanism of aluminum particle and further its applications in propellants. The physical and chemical properties of micron-aluminum particle were evaluated by scanning electron microscopy, laser particle size analyzer, X-ray diffractometer and inductively coupled plasma atomic emission spectrometer. The thermal oxidation characteristics of the sample were studied by thermal analyzer. The experimental results showed that the initial oxide thickness of the sample was about 3.96 nm, and the calculated values of the specific surface area and the active aluminum content obtained by the established mathematical model were in good agreement with the measured values. The thermal oxidation process of the sample was divided into three stages. When the temperature rose to 1100 °C, the thermal oxidation efficiency of the sample reached 98.55%. With the increase in treatment temperature, dramatic crystalline changes occurred on the surface of the sample: amorphous alumina—γ-Al₂O₃, α-Al₂O₃, and the oxide layer thickness increased from 3.96 to 5.72 nm and 31.56 nm up to 320.15 nm. When the temperature reached 700 °C, the outer surface of the oxide layer contained a small amount of α-Al₂O₃, while the interior consisted of a large amount of γ-Al₂O₃, indicating that the conversion of γ-Al₂O₃ to α-Al₂O₃ occurred from the inside out.     

Luminescence of Eu~(2 ) in Strontium Aluminum Oxide System with Long Decay Property

Luminescentmaterialshavinglongdecayperi0dhaveat-IIactedmuchinterestduetotheirpotentialwidespreadaPplicati0ns.Recently,alongdecayluminescentp0wderhavingthecomPositionofSrAl2O4activatedwithEu' wasreportedandregardedasthebestcandidateforpracticalaPPlicationbecauseofitsuniqueadVantages0veritsprecursors.l'2Inthispaper,wereportthesynthesisofthelongdecayluminescentpowderandtheinnuence0fthemolarratioofAlt0sr0ntheethessioncolor.Toproducethelundnescentp0wder,amixtureofSrCO3,Al2O3,Eu2O3andsomesol…     

Effect of atmospheric nitrogen on the oxidation mechanism of aluminum alloys with rare-earth metals

Interaction (25–620°C) of aluminum and its alloys with an atmosphere saturated with nitrogen was studied to determine the role played by rare-earth metals in the mechanism by which nitride phases are formed in oxidation of Al + REM alloys in air. The ellipsometric method and Auger electron spectroscopy were used to determine that, under the given experimental conditions, metallic aluminum is subjected to the greatest extent to the nitridation process, which is competing with the oxidation process. The process is initiated by the conversion of the amorphous oxide film to γ-Al₂O₃. The surface of Al + REM alloys interacts with nitrogen at the outer part of the oxide layer. The rare-earth metal actively reacts with impurity oxygen present in the atmosphere under study and hinders formation of nitride/oxynitride layers.     

Quantification of surface roughness effect on elastically backscattered electrons

Electron inelastic mean free path can be obtained from a measured elastic peak electron spectroscopy spectrum combined with a Monte Carlo simulation. It is thus necessary to know the influence of various experimental factors to the measured and calculated results. This work investigates the effect of the surface roughness or the surface topography on the intensity of the elastic peak. A Monte Carlo simulation, by taking into account of realistic surface roughness for both Gaussian and non‐Gaussian type rough surfaces experimentally prepared, has been employed to study the surface topography effect. The simulations of elastic peak electron spectroscopy were performed for both planar and rough Al and Cu surfaces and for varied primary energies ranging from 200 to 2000 eV. To quantify the surface roughness effect, the surface roughness parameter is introduced according to the ratio of elastic peak intensities between a rough surface and an ideal planar surface. Simulation results have shown that surface roughness parameter is important in a certain range of emission angle and particularly for large emission angles. For grazing emission, the elastic peak intensity can be largely enhanced by roughness even at nanometer scale. Copyright © 2014 John Wiley & Sons, Ltd.     

In-plane polarisation correlation study of the 31 D state of helium excited by 40 eV electrons

Electron-photon polarisation correlations measured in the scattering plane defined by the incident and scattered electron momenta are reported for 40 eV electron impact excitation of the 3¹ D state of helium and for electron scattering angles in the range 40°≦?≦120°. When combined with the results of our earlier polarisation analysis on radiation emitted perpendicular to the scattering plane, detailed information on the shape and dynamics of the exicted state is obtained. In the small angular range of overlap (40–60°) there is excellent agreement with a pervious experimental study. The behaviour of the linear polarisation of the radiation emitted in the scattering plane is well reproduced by a multichannel eikonal theory for ?≦80°. Otherwise theories totally fail to described the excitation process.     

Surface Area Study of High Area Cobalt Aluminate Particles Prepared by the Sol-Gel Method

Cobalt aluminate particles were prepared by the sol-gel method, starting from aluminum sec-butoxide and cobalt salts with a Co:Al ratio of 1:3. Samples with the same composition were also prepared by the citrate-gel method from cobalt and aluminum nitrates and citric acid. The particles were calcined to temperatures between 400 and 1000°C, for the formation of the mixed oxide having spinel structure. The surface properties of the different samples (BET surface area and pore size distribution) were measured. The highest BET surface area obtained (about 339 m²/g) corresponds to a sample prepared by cobalt acetate and aluminum sec-butoxide, calcined at 400°C. The surface area of the sample is reduced progressively as the sample is calcined to higher temperatures (to about 65 m²/g at 1000°C). Narrow pore size distributions were observed with average pore radius ranging from 17–20 Å, for samples heated to 400°C, to about 55–65 Å, for samples heated to 1000°C. The different surface areas and porosities obtained for particles prepared by different methods, different precursors or calcination temperatures, are discussed.     

Phase investigations of the AlIr system

The phase behavior of the AlIr system has been studied using differential thermal analysis, electron microprobe analysis, X-ray diffraction, chemical analysis and X-ray fluorescence. Our work confirms the existence of four compounds: Al₉Ir₂, Al₃Ir, Al_2.7Ir and AlIr. We also observed an additional intermetallic phase, with a stoichiometry corresponding to Al₁₃Ir₄; however, this compound exhibits a complex X-ray pattern and currently no structure has been determined.Peritectic temperatures were determined for Al₉Ir₂ (900 °C), Al₁₃Ir₄ (1015 °C) and Al₃Ir (1450 °C). The Al_2.7Ir phase is stable to above 1450 °C, and the congruent melting temperature of AlIr is 2120 ± 20 °C. The solubility of aluminum in iridium was measured between 1085 and 1850 °C, and the maximum solid solubility was extrapolated to 18 at.% at 2058 °C. The maximum solid solubility of iridium in aluminum was measured to be less than 0.1 at.%. A phase diagram for the AlIr system is presented.     

Molecular orbital momentum distributions and binding energies for nitric oxide

Binding energy spectra of the valence electrons of the open shell molecule NO have been obtained up to 55 eV at azimuthal angles of 0° and 7° using binary (e, 2e) spectroscopy at an impact energy of 1200 eV. The momentum distribution has been obtained for the least tightly bound (unpaired) electron, removal of which leads to formation of the X ¹Σ⁺ ground state of NO⁺. Momentum distributions have also been measured at 21.0 and 40.5 eV. The measured momentum distributions are compared with several literature wavefunctions of varying complexity. They are found to be in excellent agreement with those calculated using the natural spin orbital wavefunctions of Kouba and Ohrn.