Auger Spectroscopy Research Papers - Academia.edu (original) (raw)

The performance ofTi.3W.7 and Nb thin films as diffusion barriers for Au was investigated by Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES). The films were sputter deposited in Ar:N2 (70:30 vol%) or pure Ar on amorphous Si02. They were annealed in air at temperatures ranging from 250·C up to 750·C for several hours. In-depth profiles revealed an onset of oxidation of the barriers at 520·C for Nb and 600·C for TiW. Barrier oxidation and extensive diffusion could be correlated. Distinct diffusion behavior as a function of temperature was established between TiW and Nb. A Nb multilayer structure was found to provide the best reliability as the barrier and as the adhesion layer.

- by and +1
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- Electronic Engineering, Engineering Physics, Materials Engineering, Physics

Ti-Al-N coatings were deposited on high-speed steel substrates by filtered vacuum arc deposition (FVAD) during evaporation of aluminum and titanium cathodes. Distribution of elements, phase composition, and mechanical properties of Ti-Al-N coatings were investigated using Auger electron spectroscopy (AES), X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindentation, respectively. Additionally, tribological tests and scratch tests of the coatings were performed. The stoichiometry of the coating changes from Ti 0.6 Al 0.4 N to Ti 0.48 Al 0.52 N with increasing aluminum arc current from 70 A to 90 A, respectively. XRD and TEM showed only face-centered cubic Ti-Al-N phase with preferred orientation of the crystallites in (220) direction with respect to the sample normal and without precipitates of AlN or intermetallics inside the coatings. Incorporation of Al into the TiN lattice caused shifting of the (220) reflex to a higher 2θ angle with increasing Al content. Low content and size of microdroplets were obtained using coaxial plasma filters, which provides good mechanical and tribological properties of the coatings. The highest value of microhardness (36 GPa) and the best wear-resistance were achieved for the coating with higher Al content, thus for Ti 0.48 Al 0.52 N. These coatings exhibit good adhesive properties up to 30 N load in the scratch tests.

- by Aleksei Obrosov and +1
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- Thin Films and Coatings, Nanoindentation, Transmission Electron Microscopy, Auger Spectroscopy

Auger electron (AES), electron energy loss (EELS) and X-ray photoelectron spectroscopy (XPS) were used to identify the reaction products at the fibre-matrix interface in SiC nicalon fibre-LAS (Li2O, Al2O3, SiO2) or LAS + Nb2O5 glass matrix composites. Chemical bonding of the different elements was investigated by AES using sputter-depth profiling on fibres extracted from two matrices by etching in hydrofluoric acid. The chemistry of the silicium was studied by EELS in nicalon-LAS + Nb2O5 composite cross-sections. XPS was performed on fibres extracted from the nicalon-LAS + Nb2O5 composite to confirm EELS and AES results. These investigations show that in both composites the reaction scale at the fibre-matrix interface consists of a carbon layer next to the matrix and of a silicate phase rich in oxygen which contains carbon, probably in the form of a silicon oxycarbide, and which is located between the carbon layer and the fibre core.

- by Nicole Herbots
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- Engineering Physics, Materials Engineering, Chemical Engineering, Physics

— The efficiency limiting mechanisms in type-I GaInAsSb-based quantum well (QW) lasers, emitting at 2.3 µm, 2.6 µm and 2.9 µm, are investigated. Temperature characterization techniques and measurements under hydrostatic pressure identify an Auger process as the dominant non-radiative recombination mechanism in these devices. The results are supplemented with hydrostatic pressure measurements from three additional type-I GaInAsSb lasers, extending the wavelength range under investigation from 1.85-2.90 μm. Under hydrostatic pressure, contributions from the CHCC and CHSH Auger mechanisms to the threshold current density can be investigated separately. A simple model is used to fit the non-radiative component of the threshold current density, identifying the dominance of the different Auger losses across the wavelength range of operation. The CHCC mechanism is shown to be the dominant non-radiative process at longer wavelengths (> 2 μm). At shorter wavelengths (< 2 μm) the CHSH mechanism begins to dominate the threshold current, as the bandgap approaches resonance with the spin-orbit split-off band.

- by Shamsul Arafin
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- Semiconductor Devices, Auger Spectroscopy, Diode Lasers

We describe here an efficient machine-learning based approach for the optimization of parameters used for extracting the arrival time of waveforms, in particular those generated by the detection of 511 keV annihilation γ-rays by a 60 cm 3 coaxial high purity germanium detector (HPGe). The method utilizes a type of artificial neural network (ANN) called a self-organizing map (SOM) to cluster the HPGe waveforms based on the shape of their rising edges. The optimal timing parameters for HPGe waveforms belonging to a particular cluster are found by minimizing the time difference between the HPGe signal and a signal produced by a BaF 2 scintillation detector. Applying these variable timing parameters to the HPGe signals achieved a γ-γ coincidence timing resolution of ~ 4.3 ns at the 511 keV photo peak (defined as 511 ± 50 keV) and a timing resolution of ~ 6.5 ns for the entire γ spectrum-without rejecting any valid pulses. This timing resolution approaches the best obtained by analog nuclear electronics, without the corresponding complexities of analog optimization procedures. We further demonstrate the universality and efficacy of the machine learning approach by applying the method to the generation of secondary electron time-of-flight spectra following the implantation of energetic positrons on a sample.

- by Randall W Gladen and +2
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- Instrumentation Engineering, Artificial Intelligence, Condensed Matter Physics, Machine Learning

Many photoinduced processes including photosynthesis and human vision happen in organic molecules and involve coupled femtosecond dynamics of nuclei and electrons. Organic molecules with heteroatoms often possess an important excited-state relaxation channel from an optically allowed ππ* to a dark nπ* state. The ππ*/nπ* internal conversion is difficult to investigate, as most spectroscopic methods are not exclusively sensitive to changes in the excited-state electronic structure. Here, we report achieving the required sensitivity by exploiting the element and site specificity of near-edge soft X-ray absorption spectroscopy. As a hole forms in the n orbital during ππ*/nπ* internal conversion, the absorption spectrum at the heteroatom K-edge exhibits an additional resonance. We demonstrate the concept using the nucleobase thymine at the oxygen K-edge, and unambiguously show that ππ*/nπ* internal conversion takes place within (60 ± 30) fs. High-level-coupled cluster calculations confirm the method's impressive electronic structure sensitivity for excited-state investigations.

- by David Mogk
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- Interplanetary dust, Spectroscopy, Auger Spectroscopy, Stratosphere

We study the surface chemistry of Cd 0.96 Zn 0.04 Te(211)B by X-ray photoelectron spectroscopy and ellipsometry. We obtain first the dielectric functions of amorphous Te and Cd on Cd 0.96 Zn 0.04 Te(211)B by in situ ellipsometry after growing thin films of each material by molecular beam epitaxy. We then study their oxidation in air and show that Cd oxidizes primarily as a hydroxide whereas Te is present as TeO 2. In neither case is the oxidation of the films complete, as a substantial amount of either metallic Te or Cd remains even after several days of oxidation. We subsequently exploit an electroless chemical etchant based on Ce 4+ to produce Te-rich Cd 0.96 Zn 0.04 Te(211)B surfaces which oxidize very little in air. Another etchant containing KCN reduces the amount of aTe substantially. Finally, we construct a tentative optical model for the Cd 0.96 Zn 0.04 Te(211)B surface that yields the abundance of amorphous Te on the surface.

- by Giacomo Badano
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- Chemistry, Auger Spectroscopy, XPS, Spectroscopic Ellipsometry

The L1−L2,3M Coster-Kronig spectrum of argon has been measured by using photon excitation. The intensity ratio of 0.30±0.02 between the L1−L2,3M1 main lines and the L1−L2,3M2,3 lines is extracted from experiment. The experimental results... more

In this work, room temperature oxidation of GaAs was investigated using ion beam oxidation (mO). In lBO, an ion beam is used to introduce oxygen athermally into the substrate, in this case GaAs. GaAs bonds are broken upon collision with the ions, making gallium and arsenic atoms readily available to react with the oxygen species. Ion beam oxidation of GaAs at room temperature was studied as a function ofoxygen ion energy between 500 and is keY. The ion beam oxidized GaAs was characterized in situ by Auger electron spectroscopy (AES) and ex situ with x-ray photoelectron spectroscopy (XPS) for accurate determination of the film chemical composition. Below 1 keY, a thin oxide film is formed: it is composed of Ga20 3 and AS20 3 with almost no metallic arsenic, and presents insulating properties.
As the ion energy increases, preferential sputtering of As and decomposition of AS203 increase and prevent formation of an
insulating film. No damage was detected by Rutherford backscattering spectrometry (RES) combined with ion channeling, in the substrate subjected to IBO below 1 keV.""