276 research outputs found
Three-Dimensional X-Ray Photoelectron Tomography on the Nanoscale: Limits of Data Processing by Principal Component Analysis
Electronic and Optical Properties of Aluminum Oxide Before and After Surface Reduction by Ar+ Bombardment
The electronic and optical properties of a-Al2O3 after induced by 3-keV Ar+ sputtering have been studied quantitatively by use of reflection electron energy loss spectroscopy (REELS) spectra. The band gap values of a-Al2O3 was determined from the onset values of the energy loss spectrum to the background level of REELS spectra as a function of time Ar+ bombardment. The bandgap changes from 8.4 eV before sputtering to 6.2 eV after 4 minutes of sputtering.The optical properties of α-Al2O3 thin films have been determined by comparing the experimental cross section obtained from reflection electron energy loss spectroscopy with the theoretical inelastic scattering cross section, deduced from the simulated energy loss function (ELF) by using QUEELS-Δ(k)-REELS software. The peak assignments are based on ELF and compared with reported data on the electronic structure of α-Al2O3 obtained using different techniques. The results demonstrate that the electronic and optical properties before and after surface reduction will provide further understanding in the fundamental properties of α-Al2O3 which will be useful in the design, modeling and analysis of devices applications performance.Received: 18 November 2013; Revised:12 June 2014; Accepted: 25 June 2014
Electronic and Optical Properties of Aluminum Oxide Before and After Surface Reduction by Ar+ Bombardment
The electronic and optical properties of a-Al2O3 after induced by 3-keV Ar+ sputtering have been studied quantitatively by use of reflection electron energy loss spectroscopy (REELS) spectra. The band gap values of a-Al2O3 was determined from the onset values of the energy loss spectrum to the background level of REELS spectra as a function of time Ar+ bombardment. The bandgap changes from 8.4 eV before sputtering to 6.2 eV after 4 minutes of sputtering.The optical properties of α-Al2O3 thin films have been determined by comparing the experimental cross section obtained from reflection electron energy loss spectroscopy with the theoretical inelastic scattering cross section, deduced from the simulated energy loss function (ELF) by using QUEELS-Δ(k)-REELS software. The peak assignments are based on ELF and compared with reported data on the electronic structure of α-Al2O3 obtained using different techniques. The results demonstrate that the electronic and optical properties before and after surface reduction will provide further understanding in the fundamental properties of α-Al2O3 which will be useful in the design, modeling and analysis of devices applications performance.Received: 18 November 2013; Revised:12 June 2014; Accepted: 25 June 201
On the ultrathin gold film used as buffer layer at the transparent conductive anode/organic electron donor interface
Previously, we have shown that a gold thin film of only 0.5Â nm introduced at the interface between the indium tin oxide or ZnO anode and the organic electron donor in organic photovoltaic cells induces a strong improvement of the cell efficiency. Of course a thickness of 0.5Â nm corresponds only to an averaged thickness, the films being too thin to be continuous. For a clear understanding of the physical mechanisms that are responsible for this improved behaviour, it is important to know the fractional coverage and the island height of this thin Au film. In the present work, we have used two different techniques, such as treated scanning electron microscope images and analysis of the inelastic part of peaks of X-ray photoelectron spectroscopy spectra, to estimate the gold coverage and island height of the transparent conductive anode. There is an excellent agreement between the results achieved by both methods. Only 15% of the anode is covered, which proves the high efficiency of gold as an anode buffer layer in organic photovoltaic devices
Metoder og apparater til vandindholdsbestemmelse i korn.
Metoder og apparater til vandindholdsbestemmelse i korn
Metoder og apparater til vandindholdsbestemmelse i korn.
Metoder og apparater til vandindholdsbestemmelse i korn
Inelastic electron scattering by the gas phase in near ambient pressure XPS measurements
Xâray photoemission spectroscopy (XPS) measurements in nearâambient pressure (NAP) conditions result in a signal loss of the primary spectrum as a result of inelastic scattering of photoelectrons in the gas phase. The inelastic scattering of the primary electrons gives rise to a secondary signal that can result in additional and often unwanted features in the measured spectrum. In the present work, we derive equations that can be used to model the resulting signal and provide equations that can be used to simulate or remove the inelastic scattering signal from measured spectra. We demonstrate this process for photoemission spectra of a wide range of kinetic energies, measured from Au, Ag, and Cu, in a variety of gases (N2, He, H2, and O2). The work is supplemented with an openâsource software in which the algorithms described here have been implemented and can be used to remove the gas phase inelastic scattering signal
Bulk and surface switching in Mn-Fe-based Prussian Blue Analogues
Many Prussian Blue Analogues are known to show a thermally induced phase
transition close to room temperature and a reversible, photo-induced phase
transition at low temperatures. This work reports on magnetic measurements,
X-ray photoemission and Raman spectroscopy on a particular class of these
molecular heterobimetallic systems, specifically on
Rb0.81Mn[Fe(CN)6]0.95_1.24H2O, Rb0.97Mn[Fe(CN)6]0.98_1.03H2O and
Rb0.70Cu0.22Mn0.78[Fe(CN)6]0.86_2.05H2O, to investigate these transition
phenomena both in the bulk of the material and at the sample surface. Results
indicate a high degree of charge transfer in the bulk, while a substantially
reduced conversion is found at the sample surface, even in case of a near
perfect (Rb:Mn:Fe=1:1:1) stoichiometry. Thus, the intrinsic incompleteness of
the charge transfer transition in these materials is found to be primarily due
to surface reconstruction. Substitution of a large fraction of charge transfer
active Mn ions by charge transfer inactive Cu ions leads to a proportional
conversion reduction with respect to the maximum conversion that is still
stoichiometrically possible and shows the charge transfer capability of metal
centers to be quite robust upon inclusion of a neighboring impurity.
Additionally, a 532 nm photo-induced metastable state, reminiscent of the high
temperature Fe(III)Mn(II) ground state, is found at temperatures 50-100 K. The
efficiency of photo-excitation to the metastable state is found to be maximized
around 90 K. The photo-induced state is observed to relax to the low
temperature Fe(II)Mn(III) ground state at a temperature of approximately 123 K.Comment: 12 pages, 8 figure
Determining the Thickness and Completeness of the Shell of Polymer Core\u2013Shell Nanoparticles by X-ray Photoelectron Spectroscopy, Secondary Ion Mass Spectrometry, and Transmission Scanning Electron Microscopy
On the ultrathin gold film used as buffer layer at the transparent conductive anode/organic electron donor interface
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