The secondary-electron background problem in electron excited auger electron spectroscopy

Dynamic background subtraction is used to demonstrate that the recently suggested spline-polynomial scheme for characterizing the secondary electron background neglects an important aspect of the Auger feature. As a consequence of this neglect, area measurements using the spline approximation are difficult to relate to the true Auger current.     

Beam-foil-excited Auger transitions in neon

Energy spectra of electrons ejected from collisions between a carbon foil and Ne projectiles with energies between 1.4 and 20 MeV have been measured. Continuous and discrete electron energy distributions are observed. Auger transitions of foil-excited Ne have been studied. Using relativistic Dirac-Fock multiconfiguration calculations, most of the measured Auger transitions have been identified.     

High resolutionLMM Auger spectra of low energy from solid surfaces

LMM Auger spectra of Cl, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, and Zn have been investigated with an electrostatic cylindrical spectrometer with energy resolution of about 0.05% in the energy range of 100 eV–1 keV. The Auger electrons have been excited by 5 keV electron bombardment at a grazing incidence angle and the peak of elastically scattered primary electrons have been used for calibration. The line assignments have been discussed.     

TheK Auger spectrum of the free magnesium atom

TheK Auger spectrum of free Mg atoms has been investigated with an electrostatic energy analyzer at an energy resolution of 0.16%. The ionization in theK shell of the Mg vapour was caused by electron impact. Absolute energies and relative intensities of the normal Auger transitionsK-LL and of the most intense satellite lines have been determined. The experimental energies and relative group intensities of the normal lines agree well with theoretical values. The total intensity of special classes of satellites are compatible with calculations of the shake theory within the sudden approximation.     

Auger spectra for elements of low atomic number

KLL Auger spectra for the light elements sodium (Z=11) and magnesium (Z=12) have been studied. All five lines predicted by the extremeLS coupling theory are observed. A comparison is made with intensities predicted by the inter-configuration interaction theory ofAsaad. Agreement is obtained for the transition intensities to the three differentKLL configurations; however, theory does not give correct relative intensities within the 2s ² 2p ⁴ configuration. The measured Auger energies are compared with those calculated from the semi-empirical expression ofAsaad andBurhop and modified byHörnfeldt et al. Good agreement is obtained when we use electron binding energies measured by the ESCA method.     

TheLMM Auger spectra of some transition metals of the first series

TheLMM peaks in the Auger spectra for the first transition series are identified according to all the evidence currently available, with special reference to Fe, Co and Ni. The similarity of results obtained with different types of analyser is demonstrated.     

Optimized AC conductivity correlated to structure,morphology and thermal properties of PVDF/PVA/Nafion composites

Polyvinylidene fluoride (PVDF) and polyvinyl alcohol (PVA) composites were prepared by controlled loading of Nafion (5 to 15 wt%) by solution casting using water and dimethylformamide (DMF) as a solvent. The surface morphology of composite analyzed by atomic force microscopy (AFM) reveals the presence of Nafion ionomers. The increase in interlayer spacing of modified PVDF/PVA polymer system as a function of Nafion was detected by X-ray diffraction (XRD). The major change in Fourier transform infrared (FTIR) spectroscopy confirms the chemical bond C=O stretching around 1,700 cm^?1 due to Nafion. Differential scanning calorimetry (DSC) demonstrates the thermal stability of polymer composites and the decrease in melting temperature (T _m). The optimized AC conductivity (σ) of the prepared composite was evaluated by using an impedance analyzer as a function of temperature (40 to 150 °C) at constant 30-MHz frequency. The highest conductivity of 1.3?×?10^?2 S m^?1 was observed at 80 °C for 10 wt% of Nafion and correlated with structure, morphology and thermal properties of modified PVDF/PVA/Nafion composites. The experimental results may be useful for sensors, fuel cells and battery application domains.     

TheL- andK- Auger spectra of tellurium

TheL- andK- Auger spectra of tellurium (Z=52) were studied from the electron capture decay of¹²⁵I. The measured relativeL- Auger transition intensities are not in agreement with the theoretical intensities of Asaad for silver (Z=47). The measured relativeKLL intensities are in agreement with those ofGraham et al. Relative intensities are given for theKL Y spectrum. TheKL Y/KLL ratio was measured to be 0.44 ± 0.02 in good agreement with the theoretical value given byWapstra.K/L andL subshell conversion ratios are given for the 35 keV nuclear transition in¹²⁵Te.     

System design considerations for precision measurement of high magnetic fields by Faraday effect

Practical and technical considerations for an instrument designed to measure high magnetic fields by Faraday effect are given. Magnetic fields up to 2 Tesla were measured and the results compared to those of Nuclear Magnetic Resonance technique. Results of measurements at low temperatures are also reported.     

Surface plasmon resonance and surface-enhanced Raman scattering activity of SiO2–Au core-cap nanostructure arrays

SiO₂–Au core-cap nanostructure arrays were prepared by dip-coating technique combined with wet chemical reduction method. The surface morphologies, structures, and optical properties of the obtained samples were characterized by scanning electron microscopy, X-ray diffraction, and ultraviolet–visible spectrophotometer, respectively. The surface-enhanced Raman scattering (SERS) activity of SiO₂–Au core-cap nanostructure arrays substrates was investigated using leucine as probe molecule. And the relationship between the SERS effect and the surface plasmon resonance (SPR) peaks was discussed. High-quality, stable, and reproducible SERS spectra of leucine were successfully obtained. When the maximum SPR peak matched with the excitation wavelength, the substrate gave rise to the highest SERS enhancement. Furthermore, six different fluorescent dyes were also chosen as probe molecules. It was found that the substrate showed good Raman enhancement and highly efficient fluorescence quenching characteristic on these fluorescent dyes.     

Absolute atomic densities determined by auger electron spectroscopy

The secondary electron distributionN(E) obtained with a spherical grid retarding field analyser is stored in a multichannel analyser. The experimental intensities of Auger lines are accurately determined by numerically substracting the background in theN(E) distribution and taking the area under the resulting peaks. Broadening of the lines due to several experimental factors, the multiple structure of the lines and the characteristics energy losses are taken into account. The absolute atomic densities on the surface are deducted from the Auger line intensities by a simple theoretical model. A comparison is made with atomic densities on the surface which are known either from the crystal structure (cleaved muscovite) or from Rutherford backscattering experiments (thin layer of Ag) or simply from the specific weight in the case of bulk materials (C, Cu, Ag). The maximum deviation is smaller than a factor of 2. Generally, the values differ by about 30%, which shows that AES, performed in this way, can give reliable quantitative results for densities ranging from a fraction of a monolayer to the bulk material.     

Linewidth and auger effect in CaF2, SrF2, and BaF2

In BaF₂ crystals, the linewidth of certain core band-conduction band excitons shows strong temperature dependence, while the corresponding linewidths in CaF₂ and SrF₂ do not. Calculations of the broadening due to the temperature-independent Auger effect are in good agreement with experimental data.     

Post-collision interaction in inner-shell ionisation of ArL 3 by electron impact

The shifts and shapes of ArL ₃ Auger lines due to the post-collision interaction (PCI) in the inner-shell ionisation of theL ₃-shell of argon by electron impact have been measured for the range of excess energiesE ₁=10 to 1,500 eV. The experimental shifts {ie67-01} could be fitted by a relation {ie67-02} withc=(5.3±0.4) andn= (?0.45±0.04) whereГ(ArL ₃)=130 meV is the ArL ₃-level width. In a classical model the PCI shifts have been calculated for two limiting cases:a) whereE ₁ is large enough (E ₁>50 eV) for the motion of the two slow electrons to be treated as uncorrelated, andb) forE ₁→0. The calculated shifts forE ₁=250, 750 and 1,750 eV are in good agreement with the experimental results. Also the calculated PCI distorted shapes of Auger lines for differentE ₁ agree reasonably with the experimental Auger line shapes.     

The role of auger effect in thermostimulated phenomena in ionic crystals

Absorption and thermostimulated luminescence simultaneously with electric conductivity in KI crystals irradiated with X-rays at L.N.T. were measured. The kinetics of these and many other similar results obtained in other alkali halides are interpreted on the basis of Auger process occurring in consequence of the recombination of free holes with localized electrons inF-centers.     

Synthesis of fluorescent carbon dots from one-step pyrolysis of frontal-polymerized poly(acrylamide-co-4-vinylpyridine)

We report herein the synthesis of carbon dots (CDs) by a one-step pyrolysis from poly(acrylamide-co-4-vinylpyridine) [poly(AAM-co-4-VP)]. The poly(AAM-co-4-VP) was fabricated using frontal polymerization within 5 min in an easy and rapid way and then was pyrolyzed to afford CDs. The as-prepared CDs show crystalline structure and excellent dispersibility with particle sizes in the range of 2–4 nm. The optical properties were throughly investigated, and we found the CDs exhibit strong blue fluorescence with quantum yield of ~18 % and excellent photoluminescent stability, which is rarely influenced by the external conditions. This process can be exploited as an effective path for synthesis CDs with polymers by a facile and rapid way.     

Radiative lifetimes of some energy levels of doubly ionized Xenon

Using 1–5 MeV Xenon ions we have studied the beam-foil spectrum of Xenon between 105 nm and 500 nm. Radiative lifetimes were measured for levels of Xenon III. For those lifetimes which have been measured previously (Andersen et al. [l]) good agreement is obtained. The interpretation of the decay curves and the assignment of a measured value, were done with the help of theoretical lifetimes obtained by Coulomb-approximation calculations [2].     

Excitation lines and multiple ionization in Auger spectra

Satellite lines of a new type and excessively large continuous distributions of energy degraded electrons are observed in theKLL Auger spectra of potassium, chlorine, and sulfur. The lines are tentatively interpreted as due to a process that is characteristic of the atom more than of the entire solid and the excessive number of electrons in the continuous distributions is interpreted as due to multiple ionization.     

Plasma-assisted hot filament chemical vapor deposition of AlN thin films on ZnO buffer layer: toward highly c-axis-oriented,uniform, insulative films

c-Axis-oriented aluminum nitride (AlN) thin film with improved quality was deposited on Si(111) substrate using ZnO buffer layer by plasma-assisted hot filament chemical vapor deposition. The optical and electrical properties and surface morphology as well as elemental composition of the AlN films deposited with and without ZnO buffer layer were investigated using a host of measurement techniques: X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, field emission scanning electron microscopy (FESEM), and current–voltage (I–V) characteristic measurement. The XRD and XPS results reveal that the AlN/ZnO/Si films are free of metallic Al particles. Also, cross-sectional FESEM observations suggest formation of a well-aligned, uniform, continuous, and highly (002) oriented structure for a bi-layered AlN film when Si(111) is covered with ZnO buffer. Moreover, a decrease in full width at half maximum of the E₂ (high)-mode peak in Raman spectrum indicates a better crystallinity for the AlN films formed on ZnO/Si substrate. Finally, I–V curves obtained indicate that the electrical behavior of the AlN thin films switches from conductive to insulative when film is grown on a ZnO-buffered Si substrate.     

Depth selective conversion electron Mössbauer spectroscopy by use of a proportional counter

The depth selectivity of conversion electron Mössbauer spectroscopy by use of a proportional counter was studied in detail. For this purpose the pulse-height spectrum of conversion and Auger electrons emitted from a⁵⁷Fe absorber was measured at the resonance Doppler velocity. From the spectrum it is found that the energy settings of 2–5 keV, 6–9 keV and 11–14 keV are suitable for depth selective analysis.