| 1. |
- Aberg, D., et al.
(författare)
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Nitrogen passivation by implantation-induced point defects in 4H-SiC epitaxial layers
- 2001
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 184:04-jan, s. 263-267
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Tidskriftsartikel (refereegranskat)abstract
- Ion implantation causes damage to the crystal lattice resulting in the loss of free charge carriers. In this study, low dose implantations using different ions and implantation doses are made to resolve the initial carrier loss in nitrogen-doped epitaxial layers. A strong dependence of compensation on nitrogen concentration is seen, showing that nitrogen is passivated by implantation-induced point defects. An activation energy of 3.2 eV for the dissociation of the passivated nitrogen center is obtained.
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| 2. |
- Achermann, M, et al.
(författare)
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Carrier dynamics around nano-scale Schottky contacts: a femtosecond near-field study
- 2002
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Ingår i: Applied Surface Science. - 1873-5584. ; 190:1-4, s. 513-516
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Tidskriftsartikel (refereegranskat)abstract
- We report spatially and time-resolved measurements of ultrafast carrier dynamics around buried nano-scale Schottky contacts, performed with a novel femtosecond near-field scanning optical microscope. The experimental results are modeled by a self-consistent treatment of the drift-diffusion equation for the carriers and Poisson's equation for the built-in electric field. We show that the built-in field suppresses electron transport towards and trapping into the metal particles at lower optically excited carrier densities. In contrast, efficient electron trapping into the metal occurs at higher electron densities, which screen the built-in field, allowing for efficient transport of electrons towards the Schottky contact. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 3. |
- Agui, A., et al.
(författare)
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Direct observation of interface effects of thin AlAs(100) layers buried in GaAs
- 2000
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 166:1-4, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- A study of the electronic structure of ultrathin AlAs layers buried in GaAs(100) and their interfaces is presented. Al L2,3 soft-X-ray-emission (SXE) spectra from the AlAs layers were measured. The spectra show distinct thickness-dependent features, which are reproduced using ab initio calculations.
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| 4. |
- Amandusson, H., et al.
(författare)
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Effect of CO and O2 on hydrogen permeation through a palladium membrane
- 2000
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 153:4, s. 259-267
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen permeation through a 25-µm thick palladium membrane during continuous exposures of hydrogen together with different combinations of oxygen and carbon monoxide has been studied at membrane temperatures of 100 °C-250 °C (total pressures of 40-150 Torr). Both CO and O2, individually, inhibit hydrogen permeation through the membrane. The cause of the inhibition is, however, somewhat different. CO blocks available hydrogen dissociation sites, while oxygen both blocks dissociation sites and also consumes adsorbed hydrogen through the production of water. When a combination of CO and O2 is supplied together with hydrogen, new reaction pathways will emerge. The carbon dioxide formation will dominate the water forming reaction, and consequently, the blocking effect caused by the formation of water will be suppressed. In a mixture of CO+O2+H2, the hydrogen permeation can become either larger or smaller than that due to only O2+H2 or CO+H2 depending on the CO/O2 ratio. It is thus possible to find a situation where carbon monoxide and oxygen react to form CO2 leaving adsorbed hydrogen free to permeate the membrane.
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| 5. |
- Anghel, Clara, et al.
(författare)
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Gas phase analysis of CO interactions with solid surfaces at high temperatures
- 2004
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 233:1-4, s. 392-401
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Tidskriftsartikel (refereegranskat)abstract
- An in situ method including mass spectrometry and labeled gases is presented and used to gain information on adsorption of molecules at high temperatures (>300 degreesC). Isotopic exchange rate in H-2 upon exposure to an oxidized zicaloy-2 sample and exchange rate in CO upon exposure to various materials have been measured. From these measurements, molecular dissociation rates in respective system have been calculated. The influence of CO and N-2 on the uptake rate of H-2 in zirconium and oxidized zicaloy-2 is discussed in terms of tendency for adsorption at high temperatures. In the case of oxidized Cr exposed to CO gas With C-12, C-13, O-16 and O-18, the influence of H2O is investigated with respect to dissociation of CO molecules. The presented data supports a view of different tendencies for molecular adsorption of H2O, CO, N-2, and H-2 molecules on surfaces at high temperatures.
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| 6. |
- Bexell, U., et al.
(författare)
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A ToF-SIMS study of linseed oil bonded to mercapto silane treated aluminium
- 2004
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 231-2, s. 362-365
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Tidskriftsartikel (refereegranskat)abstract
- ToF-SIMS has been used to analyse an aluminium surface treated with a vegetable oil using a mercapto silane as a coupling agent between the aluminium substrate and the vegetable oil. The coupling between the vegetable oil and the mercapto silane was obtained through a photoinduced thiol-ene reaction using UV-radiation. The ToF-SIMS results show that the desired thiolene reaction has taken place between the unsaturated parts of the vegetable oil and the thiol groups of the mercapto silane via the thiol-ene reaction forming a surface film.
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| 7. |
- Bexell, Ulf, et al.
(författare)
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Tribological Characterisation of an Organic Coating by the use of ToF-SIMS
- 2003
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 203-204, s. 596-599
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Tidskriftsartikel (refereegranskat)abstract
- ToF-SIMS has been used to analyse tribological induced chemical changes of organic coatings deposited on steel strip hot-dip coated with a 55.0% Al–43.4% Zn–1.6% Si alloy (Aluzink). The organic coating was a styrene–acrylic co-polymer containing different forming additives. The forming properties of the organic coatings were evaluated with modified scratch testing. The friction curves show that organic coated hot-dip coated steel displays significantly better tribological properties, i.e. lower coefficient of friction and lower wear, as compared to hot-dip coated steel. Furthermore, the organic coatings showing the highest material transfer tendency also show the highest wear. ToF-SIMS spectra show that a transfer film consisting of species from the organic coating is formed on the ball counter surface. Finally, a combination of SEM and ToF-SIMS analysis shows that mechanical failure of the coating dominates, i.e. no tribochemical changes of the coatings could be detected in the wear track.
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| 8. |
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| 9. |
- Bjorklund, Robert, et al.
(författare)
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Photodesorption of fulvic acid from iron oxide surfaces into aqueous solutions
- 2001
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 174:2, s. 166-175
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Tidskriftsartikel (refereegranskat)abstract
- Photodesorption of thin films of fulvic acid adsorbed on planar iron oxide surfaces was monitored by ellipsometry. Description was first observed at 546 nm, and additional fractions of the adsorbed acid left the surfaces at 405 and 365 nm Similar kinetics for photodesorption was observed from metallic iron films and from porous iron oxide prepared electrochemically by deposition on porous silicon substrates. Soluble photoproducts leaving the surface H ere monitored by UV absorbance spectroscopy at 200 nm Gaseous products were not detected by mass spectrometry but the results seemed to indicate that net all of the photoproducts entered the liquid phase. Of the metal films tested which adsorbed fulvic acid from aqueous solution (Fe. Cr, Ni, Al, and Pt), it was only iron which exhibited a photodesorption effect. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 10. |
- Bratus, V. Y., et al.
(författare)
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Vacancy-related defects in ion-beam and electron irradiated 6H-SiC
- 2001
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Ingår i: Applied Surface Science. - 0169-4332 .- 1873-5584. ; 184:04-jan, s. 229-236
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Tidskriftsartikel (refereegranskat)abstract
- A brief review is given on EPR study of irradiation-induced defects in SiC. The results of low-temperature study of Ky1 and Ky2 centers reveal for both of them the C-S symmetry, spin S = 1/2 and close coincidence of the g-tensor components. For Ky2 defect the principal values of g-tensor have been determined as g(z) = 2.0048, g(x) = 2.0022 and g(y) = 2.0037, where z and x directions reside in the (11 (2) over bar0) plane and the z-axis makes up an angle 65 degrees with the c-axis. The same residence of z- and x-axis and an angle 59 degrees are found for Ky1 center, g(z) = 2.0058, g(x) = 2.0025 and g(y) = 2.0023. A comparison of experimental and calculated hyperfine (HF) parameters is presented which suggests that Ky2 and Ky1 defects can be assigned to the positively charged carbon vacancy in 6H-SiC. The EPR study of defects created along the Al+ ion track in n-type 6H-SiC shows that lineshape, linewidth and integral intensity of the EPR signal reflect the state of damaged layer generated by ion implantation. A variation of defect density with annealing is reported and defect origin is discussed.
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