| 1. |
- Moberg, Christina, et al.
(författare)
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De unga gör helt rätt när de stämmer staten
- 2022
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Ingår i: Aftonbladet. - 1103-9000.
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- 1 620 forskare och lärare i forskarvärlden: Vi ställer oss bakom Auroras klimatkrav
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| 2. |
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| 3. |
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| 4. |
- Engberg, David L. J., et al.
(författare)
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Solid Solution and Segregation Effects in Arc-Deposited Ti1-xSixN Thin Films Resolved on the nanometer scale by 15N Isotopic Substitution in AtomP robe Tomography
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Nanostructured TiSiN is an important material in wear--‐resistant coatings for extending the lifetime of cutting tools. Yet, the understanding regarding the structure, phase composition, and bonding on the detailed nanometer scale, which determines the properties of TiSiN, is lacking. This limits our understanding of the growth phenomena and eventually a larger exploitation of the material. By substituting natN2 with 15N2 during reactive arc deposition of TiSiN thin films, atom probe tomography (APT) gives elemental sensitivity and sub-nanometer resolution, a finer scale than what can be obtained by commonly employed energy dispersive electron spectroscopy in scanning transmission electron microscopy. Using a combination of analytical transmission electron microscopy and APT we show that arc-deposited Ti0.92Si0.0815N and Ti0.81Si0.1915N exhibit Si segregation on the nanometer scale in the alloy films. APT composition maps and proximity histograms from domains with higher than average Ti content show that the TiN domains contain at least ~2 at. % Si for Ti0.92Si0.08N and ~5 at. % Si for Ti0.81Si0.19N, thus confirming the formation of solid solutions. The formation of relatively pure SiNy domains in the Ti0.81Si0.19N films is tied to pockets between microstructured, columnar features in the film. Finer SiNy enrichments seen in APT possibly correspond to tissue layers around TiN crystallites, thus effectively hindering growth of TiN crystallites, causing TiN renucleation and thus explaining the featherlike nanostructure within the columns of these films. For the stoichiometry of the TiN phase, we establish a global under stoichiometry, in accordance with the tendency for SiNy films to have tetrahedral bonding coordination towards a nominal Si3N4 composition.
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| 5. |
- Eriksson, Anders, et al.
(författare)
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Arc deposition of Ti–Si–C–N thin films from binary and ternary cathodes — Comparing sources of C
- 2012
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 213, s. 145-154
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Tidskriftsartikel (refereegranskat)abstract
- Ti–Si–C–N thin films with composition of 1–11 at.% Si and 1–20 at.% C have been deposited onto cemented carbide substrates by arcing Ti–Si cathodes in a CH4 + N2 gas mixture and, alternatively, through arcing Ti–Si–C cathodes in N2. Films of comparable compositions from the two types of cathodes have similar structure and properties. Hence, C can be supplied as either plasma ions generated from the cathode or atoms from the gas phase with small influence on the structural evolution. Over the compositional range obtained, the films were dense and cubic-phase nanocrystalline, as characterized by X-ray diffraction, ion beam analysis, and scanning and transmission electron microscopy. The films have high hardness (30–40 GPa by nanoindentation) due to hardening from low-angle grain boundaries on the nanometer scale and lattice defects such as growth-induced vacancies and alloying element interstitials.
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| 6. |
- Eriksson, Mats, 1963-, et al.
(författare)
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The water-forming reaction on thin, SiO2 supported, palladium films
- 1990
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Ingår i: Vacuum. - 0042-207X .- 1879-2715. ; 41:1-3, s. 137-138
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Tidskriftsartikel (refereegranskat)abstract
- The water-forming reaction has been studied on thin Pd films, evaporated on planar SiO2 substrates. The nominal film thickness varied between 5 and 100 Å. The studies were performed in uhv by means of mass spectrometry, UPS and work function measurements in the temperature range 323–523 K. The film structure was also studied with TEM. The results are compared with previous measurements on 1000 Å, thick, homogeneous Pd films. The structure of the thin Pd films changed dramatically during cyclic H2 and O2 exposures, from that of a continuous film with cracks to that of drop-like metal particles. These structural changes are not observed on the thick (1000 Å) Pd films. Even though there are large structural changes, the water-forming reaction looks qualitatively the same as on a thick Pd film. The total water production however, decreases with decreasing film thickness. We believe that some minor qualitative differences in the water-forming reaction for different nominal Pd film thicknesses, are due to the increasing PdSiO2 boundary as the thickness is reduced.
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| 7. |
- Falk, Lars, et al.
(författare)
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Severe Lung Dysfunction and Pulmonary Blood Flow during Extracorporeal Membrane Oxygenation
- 2024
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Ingår i: Journal of Clinical Medicine. - 2077-0383. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Extracorporeal membrane oxygenation (ECMO) is indicated for patients with severe respiratory and/or circulatory failure. The standard technique to visualize the extent of pulmonary damage during ECMO is computed tomography (CT). Purpose: This single-center, retrospective study investigated whether pulmonary blood flow (PBF) measured with echocardiography can assist in assessing the extent of pulmonary damage and whether echocardiography and CT findings are associated with patient outcomes. Methods: All patients (>15 years) commenced on ECMO between 2011 and 2017 with septic shock of pulmonary origin and a treatment time >28 days were screened. Of 277 eligible patients, 9 were identified where both CT and echocardiography had been consecutively performed. Results: CT failed to indicate any differences in viable lung parenchyma within or between survivors and non-survivors at any time during ECMO treatment. Upon initiation of ECMO, the survivors (n = 5) and non-survivors (n = 4) had similar PBF. During a full course of ECMO support, survivors showed no change in PBF (3.8 ± 2.1 at ECMO start vs. 7.9 ± 4.3 L/min, p = 0.12), whereas non-survivors significantly deteriorated in PBF from 3.5 ± 1.0 to 1.0 ± 1.1 L/min (p = 0.029). Tidal volumes were significantly lower over time among the non-survivors, p = 0.047. Conclusions: In prolonged ECMO for pulmonary septic shock, CT was not found to be effective for the evaluation of pulmonary viability or recovery. This hypothesis-generating investigation supports echocardiography as a tool to predict pulmonary recovery via the assessment of PBF at the early to later stages of ECMO support.
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| 8. |
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| 9. |
- Frodelius, Jenny, 1978-
(författare)
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Thick and Thin Ti2AlC Coatings
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This Thesis explores the deposition techniques of magnetron sputtering and high velocity oxy-fuel (HVOF) spraying for Ti2AlC as a promising high-temperature material. Magnetron sputtering aims at producing thin (≤1 μm) Ti2AlC films of high crystal quality for use as a model system in understanding the material’s basic properties. HVOF is a new method for deposition of thick (≥200 μm) coatings by spraying Ti2AlC powder, with the aim of transferring the good bulk properties to coatings. The oxidation behavior of Ti2AlC coatings has been investigated for temperatures up to 1200 °C in air. As-deposited Ti2AlC(0001) thin films decompose into TiC during vacuum annealing at 700 °C by out-diffusion of Al as shown by x-ray diffraction analysis. The release of Al starts already at 500 °C in ambient air as driven by aluminum oxide formation on the film surface where the oxide initially forms clusters as observed by electron microscopy. While sputtering from a Ti2AlC target is simpler than by using different elemental targets, the resulting film composition differs from the target stoichiometry. This is due to differences in energy and angular distribution of the sputtered species and evaporation of Al at substrate temperatures above 700 °C. The composition can be compensated for by adding Ti to bind the Al and obtain phase-pure Ti2AlC coatings. For HVOF, I demonstrate how the total gas flow of a H2/O2 mixture (441-953 liter/min) and the powder grain size (30-56 μm) determine the thickness, density, and microstructure of the coatings. High gas flow and small grain size yield thick coatings of 210 μm with a low porosity of 2-8 % and a tensile stress of ≥80 MPa. A fraction of the Ti2AlC powder decomposes during spraying into TiC, Ti3AlC2, and Ti-Al alloys. The coatings also contain as much as 25 at.% O since the powder partly oxidizes during the spraying process. Increasing the powder size and decreasing the total gas flow yield a higher amount of Ti2AlC, but produces thinner coatings with lower cohesion. Post-annealing of the coatings at 900 °C in vacuum increases the Ti2AlC content due to a reversible phase transformation of the as-sprayed material. The high oxygen content, however, hinders the coating to completely transform into Ti2AlC and deteriorates its oxidation resistance. The work thus offers insights to the key parameters for optimizing Ti2AlC coating processing.
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| 10. |
- Ghafoor, Naureen, et al.
(författare)
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Nanolabyrinthine ZrAlN thin films by self-organization of interwoven single-crystal cubic and hexagonal phases
- 2013
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Ingår i: APL Materials. - New York, USA : American Institute of Physics (AIP). - 2166-532X. ; 1:2, s. 022105-1-022105-6
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Tidskriftsartikel (refereegranskat)abstract
- Self-organization on the nanometer scale is a trend in materials research. Thermodynamic driving forces may, for example, yield chessboard patterns in metal alloys[Y. Ni and A. G. Khachaturyan, Nature Mater. 8, 410–414 (2009)] or nitrides [P. H.Mayrhofer, A. Horling, L. Karlsson, J. Sj ¨ ol¨ en, T. Larsson, and C. Mitterer, Appl. ´Phys. Lett. 83, 2049 (2003)] during spinodal decomposition. Here, we explore theZrN-AlN system, which has one of the largest positive enthalpies of mixing amongthe transition metal aluminum nitrides [D. Holec, R. Rachbauer, L. Chen, L. Wang,D. Luefa, and P. H. Mayrhofer, Surf. Coat. Technol. 206, 1698–1704 (2011); B.Alling, A. Karimi, and I. Abrikosov, Surf. Coat. Technol. 203, 883–886 (2008)].Surprisingly, a highly regular superhard (36 GPa) two-dimensional nanolabyrinthinestructure of two intergrown single crystal phases evolves during magnetron sputter thin film synthesis of Zr0.64Al0.36N/MgO(001). The self-organization is surfacedriven and the synergistic result of kinetic limitations, where the enthalpy reductionbalances both investments in interfacial and elastic energies.
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| 11. |
- Ghafoor, Naureen, et al.
(författare)
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Self-organized Labyrinthine Nanostructure in Zr0.64Al0.36N Thin Films
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Self-organization of functional ceramics on the nanometer scale drives scientific and technological research in such diverse fields as cutting tools and light-emitting diodes. A classic example is spinodal decomposition in TiAlN thin films, which yields intricate nanostructures from the isostructural decomposition into cubic-structrure (c) AlN and TiN domains, resulting in age hardening [1]. Here, we explore the ZrN-AlN system, which has one of the largest positive enthalpies of mixing among the systems combining a transition metal nitride and a wide-band gap nitride [2]. Interestingly, an original nanolabyrinthine structure evolves during thin film synthesis of Zr0.64Al0.36N. It consists of the non-isostructural phases c-ZrN and wurtzite-AlN with standing {110}‖{112̄0} planes.The selforganization in this system is discussed in terms of a competition between interfacial and surface elastic energy, which produces a structure with a well-defined length scale. This effective nanostructural design yields films with hardnesses of 36 GPa, 44 % higher than comparable ZrN films.
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| 12. |
- Goyenola, Cecilia, et al.
(författare)
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Theoretical prediction and synthesis of CSxFy thin films
- 2016
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 120:17, s. 9527-9534
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Tidskriftsartikel (refereegranskat)abstract
- A new carbon-based compound: CSxFy was addressed by density functional theory calculations and synthesized by reactive magnetron sputtering. Geometry optimizations and energy calculations were performed on graphene-like model systems containing sulfur and fluorine atoms. It is shown that [S+F] concentrations in the range of 0−10 at.%, structural ordered characteristics similar to graphene pieces containing ring defects are energetically feasible. The modeling predicts that CSxFy thin films with graphite and fullerene-like characteristics may be obtained for the mentioned concentration range. Accordingly, thin films were synthesized from a graphite solid target and sulfur hexafluoride as reactive gas. In agreement with the theoretical prediction, transmission electron microscopy characterization and selected area electron diffraction confirmed the presence of small ordered clusters with graphitic features in a sample containing 0.4 at.% of S and 3.4 at.% of F.
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| 13. |
- Halim, Joseph, et al.
(författare)
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Transparent Conductive Two-Dimensional Titanium Carbide Epitaxial Thin Films
- 2014
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Ingår i: Chemistry of Materials. - : American Chemical Society. - 0897-4756 .- 1520-5002. ; 26:7, s. 2374-2381
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Tidskriftsartikel (refereegranskat)abstract
- Since the discovery of graphene, the quest for two-dimensional (2D) materials has intensified greatly. Recently, a new family of 2D transition metal carbides and carbonitrides (MXenes) was discovered that is both conducting and hydrophilic, an uncommon combination. To date MXenes have been produced as powders, flakes, and colloidal solutions. Herein, we report on the fabrication of similar to 1 x 1 cm(2) Ti3C2 films by selective etching of Al, from sputter-deposited epitaxial Ti3AlC2 films, in aqueous HF or NH4HF2. Films that were about 19 nm thick, etched with NH4HF2, transmit similar to 90% of the light in the visible-to-infrared range and exhibit metallic conductivity down to similar to 100 K. Below 100 K, the films resistivity increases with decreasing temperature and they exhibit negative magnetoresistance-both observations consistent with a weak localization phenomenon characteristic of many 2D defective solids. This advance opens the door for the use of MXenes in electronic, photonic, and sensing applications.
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| 14. |
- Halim, Joseph, et al.
(författare)
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X-ray Photoelectron Spectroscopy Characterization of Two-Dimensional Titanium Metal Carbides (MXenes)
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Herein, we report X-ray Photoelectron Spectroscopy (XPS) analysis for cold pressed exfoliated 2D nanocrystals of transition metal carbides, MXenes. MXenes are a recently discovered family of 2D materials produced by selective chemical etching of the A element from MAX phases which are ternary metal carbides and nitrides. The latter has the formula of Mn+1AXn, where M is an early transition metal, A is an A-group element, and X is C and/or N. This study is a comparison between two MXenes, Ti3C2Tx and Ti2CTx, where Tx stands for surface termination groups such as –O, –OH, and –F. Ti3C2Tx and Ti2CTx were prepared by immersion of Ti3AlC2 and Ti2AlC powders in 50% conc. HF. A thorough XPS analysis was performed through peak fitting of high resolution XPS spectra and valence band, VB, spectra analysis. The effect of Ar sputtering as well as the number of layers n was the primarily interest of this study. According to the peak fitting analysis, both phases contain the following species, Ti–C, C–C, Ti–F, Ti–O and Ti–OH resulting in the following chemical formulas: Ti3C2(OH)x(O)y(F)z and Ti2C(OH)x(O)y(F)z. Comparing the VB spectra with the DOS calculations show the valance band spectra is actually a mixture of MXene with various terminations of OH, O and F. Before Ar+ sputtering both phases show a large percentage of fluorinated-TiO2 which is due to MXene surface oxidation as well as CHx, C-O and COO groups arising from either surface contaminations or due to drying the etched powders in ethanol after washing the powder of the HF acid. According to the VB spectra, it is shown that the fluorinated TiO2 is actually a mixture of anatase and rutile. The number of layers, n, also plays a role; the lower n, the more the MXene is prone to oxidation.
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| 15. |
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| 16. |
- Högberg, Hans, et al.
(författare)
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Reactive sputtering of CSx thin solid films using CS2 as precursor
- 2020
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Ingår i: Vacuum. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X .- 1879-2715. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- We deposit CSx thin solid films by reactive direct current magnetron sputtering of a C target in an argon plasma, using carbon disulfide (CS2) as a precursor to film growth. We investigate the influence of the partial pressure of the CS2 vapor introduced into the plasma on the composition, the chemical bonding structure, the structural, and the mechanical properties as determined by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), and nanoindentation for films deposited at 150 and 300 degrees C. The Raman and the XPS results indicate that S atoms are incorporated in mostly sp(2) bonded C network. These results agree with previous ab-initio theoretical findings obtained by modeling of the CSx compound by the Synthetic Growth Concept. The microstructure of the films as well as the results of their Raman characterization and the nano mechanical testing results all point out that with the increasing S content some spa bonding is admixed in the predominantly sp(2) bonded CSx network, leading to typical amorphous structure with short and interlocked graphene-like planes for S contents between 2% and 8%. We conclude that CSx thin solid films deposited by using CS2 as a precursor would be CSx films deposited at low temperature of similar to 150 degrees C and with an S content in the region of 6 at.% may be interesting candidates for applications as hard/elastic protective coatings.
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| 17. |
- Johnson, Lars, et al.
(författare)
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Blind deconvolution of time-of-flight mass spectra from atom probe tomography
- 2013
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 1879-2723 .- 0304-3991. ; 132, s. 60-64
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Tidskriftsartikel (refereegranskat)abstract
- A major source of uncertainty in compositional measurements in atom probe tomography stems from the uncertainties of assigning peaks or parts of peaks in the mass spectrum to their correct identities. In particular, peak overlap is a limiting factor, whereas an ideal mass spectrum would have peaks at their correct positions with zero broadening. Here, we report a method to deconvolute the experimental mass spectrum into such an ideal spectrum and a system function describing the peak broadening introduced by the held evaporation and detection of each ion. By making the assumption of a linear and time-invariant behavior, a system of equations is derived that describes the peak shape and peak intensities. The model is fitted to the observed spectrum by minimizing the squared residuals, regularized by the maximum entropy method. For synthetic data perfectly obeying the assumptions, the method recovered peak intensities to within +/- 0.33 at%. The application of this model to experimental APT data is exemplified with Fe-Cr data. Knowledge of the peak shape opens up several new possibilities, not just for better overall compositional determination, but, e.g., for the estimation of errors of ranging due to peak overlap or peak separation constrained by isotope abundances. (C) 2013 Elsevier By. All rights reserved.
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| 18. |
- Johnson, Lars, 1983-
(författare)
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Inside The Miscibility Gap : Nanostructuring and Phase Transformations in Hard Nitride Coatings
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is concerned with self-organization phenomena in hard and wear resistant transition-metal nitride coatings, both during growth and during post deposition thermal annealing. The uniting physical principle in the studied systems is the immiscibility of their constituent parts, which leads, under certain conditions, to structural variations on the nanoscale. The study of such structures is challenging, and during this work atom probe tomography (apt) was developed as a viable tool for their study. Ti0.33Al0.67N was observed to undergo spinodal decomposition upon annealing to 900 °C, by the use of apt in combination with electron microscopy. The addition of C to TiSiN was found to promote and refine the feather-like microstructure common in the system, with an ensuing decrease in thermal stability. An age-hardening of 36 % was measured in arc evaporated Zr0.44Al0.56N1.20, which was a nanocomposite of cubic, hexagonal, and amorphous phases. Magnetron sputtering of Zr0.64Al0.36N at 900 °C resulted in a self-organized and highly ordered growth of a two-dimensional two-phase labyrinthine structure of cubic ZrN and wurtzite AlN.The structure was analyzed and recovered by apt, although the ZrN phase suffered from severe trajectory aberrations, rendering only the Al signal useable.The initiation of the organized growth was found to occur by local nucleation at 5-8 nm from the substrate, before which random fluctuations in Al/Zr content increased steadily from the substrate. Finally, the decomposition of solid-solution TiB0.33N0.67 was found, by apt, to progress through the nucleation of TiB0.5N0.5 and TiN, followed by the transformation of the former into hexagonal TiB2.
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| 19. |
- Johnson, Lars, 1983-, et al.
(författare)
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Microstructure evolution and age hardening in (Ti,Si)(C,N) thin films deposited by cathodic arc evaporation
- 2010
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 519:4, s. 1397-1403
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Tidskriftsartikel (refereegranskat)abstract
- Ti1 − xSixCyN1 − y films have been deposited by reactive cathodic arc evaporation onto cemented carbide substrates. The films were characterized by X-ray diffraction, elastic recoil detection analysis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, electron-energy loss spectroscopy and nanoindentation. Reactive arc evaporation in a mixed CH4 and N2 gas gave films with 0 ≤ x ≤ 0.13 and 0≤y≤0.27. All films had the NaCl-structure with a dense columnar microstructure, containing a featherlike pattern of nanocrystalline grains for high Si and C contents. The film hardness was 32–40GPa. Films with x > 0 and y > 0 exhibited age-hardening up to 35–44 GPa when isothermally annealed up to 900 °C. The temperature threshold for over-ageing was decreased to 700 °C with increasing C and Si content, due to migration of Co, W and Cr from the substrate to the film, and loss of Si. The diffusion pathway was tied to grain boundaries provided by the featherlike substructure.
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| 20. |
- Johnson, Lars, 1983-
(författare)
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Nanostructuring and Age Hardening in TiSCN, ZrAlN, and TiAlN Thin Films
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores nanostructuring in TiSiCN, ZrAlN, and TiAlN thin films deposited by cathodic arc evaporation onto cemented carbide substrates, with intended applications for cutting tools. The three systems were found to exhibit age hardening upon annealing, by different mechanisms, into the superhard regime (≥30 GPa), as determined by a combination of electron microscopy, X-ray diffraction, atom probe tomography, erda, and nanoindentation tech- niques. TiSiCN forms nanocomposite films during growth by virtue of Si segregation to the surface of TiCN nanocrystallites while simultaneously pro- moting renucleation. Thus, the common columnar microstructure of TiCN and low-Si-content (≤5 at. %) TiSiN-films is replaced by a “feather-like” nanos- tructure in high-Si-content (≥10 at. %) TiSiCN films. The presence of C promotes the formation of this structure, and results in an accelerated age hardening beginning at temperatures as low as 700 °C. The thermal stability of the TiSiCN films is, however, decreased compared to the TiSiN system by the loss of Si and interdiffusion of substrate species; C was found to ex- acerbate these processes, which became active at 900 °C. The ZrAlN system forms a two-phase nanostructure during growth consisting of cubic ZrAlN and wurtzite ZrAlN. Upon annealing to 1100 °C, the c-Zr(Al)N portion of the films recovers and semicoherent brick-like w-(Zr)AlN structures are formed. Age hardening by 36 % was obtained before overageing sets in at 1200 °C. As-deposited and annealed solid solution Ti0.33Al0.67N thin films were characterized for the first time by atom probe tomography. The as-deposited film was found to be at the very initial stage of spinodal decomposition, which continued during annealing of the film at 900 °C for 2 h. N preferentially segregates to Al-rich domains in the annealed sample, causing a compositional variation between Ti-rich and Al-rich domains, to maintain the stoichiometry for the developing AlN phase. That effect also compensates for some of the coherency strain formed between cubic domains of TiN and AlN. Finally, a possible Kirkendall effect caused by an imbalance in the metal interdiffusion during the spinodal decomposition was discovered.
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| 21. |
- Johnson, Lars, et al.
(författare)
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Phase Transformation of Ti(B,N) into TiB2 and TiN Studied by Atom Probe Tomography
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The phase transformation of supersaturated solid-solution cubic (c) Ti0.57(B0.28N0.72)0.43 thin films into the equilibrium phases TiN and TiB2 has been studied by a combination of X-ray diffraction, transmission electron microscopy, and atom probe tomography. The transformation was found to progress through nucleation and growth, first of TiN and c-TiB0.5N0.5, followed by transformation of the B-rich precipitates to TiB2. The two-step process is interpreted as Guinier-Preston zone formation due to the incoherency between c-TiN and hexagonal TiB2. The nucleation was furthermore observed to be unclassical, with non-equilibrium compositions and extensive interfacial regions in the nuclei.
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| 22. |
- Johnson, Lars, et al.
(författare)
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Self-organized nanostructuring in Zr0.69Al0.31N thin films studied by atom probe tomography
- 2016
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 615, s. 233-238
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Tidskriftsartikel (refereegranskat)abstract
- We have applied atom probe tomography (APT) to analyze self-organizing structures of wear-resistant Zr0.69Al0.31N thin films grown by magnetron sputtering. Transmission electron microscopy shows that these films grow as a three-dimensional nanocomposite, consisting of interleaved lamellae in a labyrinthine structure, with an in-plane size scale of ~ 5 nm. The structure was recovered in the Al APT signal, while the Zr and N data lacked structural information. The onset of the self-organized labyrinthine growth was observed to occur by surface nucleation, 5–8 nm above the MgO substrate, due to increasing Zr–Al compositional fluctuations during elemental segregation. At a final stage, the labyrinthine growth mode was observed to be interrupted by the formation of larger ZrN grains.
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| 23. |
- Johnson, Lars, et al.
(författare)
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Spinodal decomposition of Ti0.33Al0.67N thin films studied by atom probe tomography
- 2012
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 520:13, s. 4362-4368
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Tidskriftsartikel (refereegranskat)abstract
- Details of the phase decomposition in NaCl-structure Ti0.33Al0.67N thin films deposited by cathodic arc evaporation are studied by atom probe tomography. We demonstrate that as-deposited films are in the earliest stage of decomposition for which electron microscopy and x-ray diffraction indicate a single-phase solid solution. Annealing at 900 degrees C further activates spinodal decomposition of the films, although pockets of unde-composed material remain after 2 h. N preferentially segregates to the AlN and TiN domains, causing the TiAlN matrix to be understoichiometric, by the energetics of N vacancies in TiAlN. The corresponding modulation in stoichiometry implies a Kirkendall effect, caused by different Al and Ti diffusivities.
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| 24. |
- Knutsson, Axel, et al.
(författare)
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Microstructure evolution during the isostructural decomposition of TiAlN : a combined in-situ small angle x-ray scattering and phase field study
- 2013
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 113:21
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes details of the spinodal decomposition and coarsening in metastable cubic Ti0.33Al0.67N and Ti0.50Al0.50N coatings during isothermal annealing, studied by in-situ small angle x-ray scattering, in combination with phase field simulations. We show that the isostructural decomposition occurs in two stages. During the initial stage, spinodal decomposition, of the Ti0.50Al0.50N alloy, the phase separation proceeds with a constant compositional wavelength of ∼2.8 nm of the AlN- and TiN-rich domains. The time for spinodal decomposition depends on annealing temperature as well as alloy composition. After the spinodal decomposition, the coherent cubic AlN- and TiN-rich domains coarsen. The coarsening rate is kinetically limited by diffusion, which allowed us to estimate the diffusivity and activation energy of the metals to 1.4 × 10−6 m2 s−1 and 3.14 eV at−1, respectively.
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| 25. |
- Lai, Chung-Chuan, et al.
(författare)
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Structural and chemical determination of the new nanolaminated carbide Mo2Ga2C from first principles and materials analysis
- 2015
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Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 99, s. 157-164
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Tidskriftsartikel (refereegranskat)abstract
- Following our recent discovery of a new nanolaminated carbide, Mo2Ga2C, we herein present a detailed structural and chemical analysis of this phase based on ab initio calculations, X-ray photoelectron spectroscopy, high resolution scanning transmission electron microscopy, and neutron powder diffraction. Calculations suggest an energetically and dynamically stable structure for C in the octahedral sites between the Mo layers, with Ga bilayers - stacked in a simple hexagonal arrangement - between the Mo2C layers. The predicted elastic properties are below those of the related nanolaminate Mo2GaC. The predicted structure, including lattice parameters and atomic positions, is experimentally confirmed. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 26. |
- Lai, Chung-Chuan, et al.
(författare)
-
Synthesis and properties of CSxFy thin films deposited by reactive magnetron sputtering in an Ar/SF6 discharge
- 2017
-
Ingår i: Journal of Physics. - : IOP PUBLISHING LTD. - 0953-8984 .- 1361-648X. ; 29:19
-
Tidskriftsartikel (refereegranskat)abstract
- A theoretical and experimental study on the growth and properties of a ternary carbon-based material, CSxFy, synthesized from SF6 and C as primary precursors is reported. The synthetic growth concept was applied to model the possible species resulting from the fragmentation of SF6 molecules and the recombination of S-F fragments with atomic C. The possible species were further evaluated for their contribution to the film growth. Corresponding solid CSxFy thin films were deposited by reactive direct current magnetron sputtering from a C target in a mixed Ar/SF6 discharge with different SF6 partial pressures (P-SF6). Properties of the films were determined by x-ray photoelectron spectroscopy, x-ray reflectivity, and nanoindentation. A reduced mass density in the CSxFy films is predicted due to incorporation of precursor species with a more pronounced steric effect, which also agrees with the low density values observed for the films. Increased P-SF6 leads to decreasing deposition rate and increasing density, as explained by enhanced fluorination and etching on the deposited surface by a larger concentration of F/F-2 species during the growth, as supported by an increment of the F relative content in the films. Mechanical properties indicating superelasticity were obtained from the film with lowest F content, implying a fullerene-like structure in CSxFy compounds.
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| 27. |
- Lauridsen, Jonas, et al.
(författare)
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Deposition of Ti-Si-C-Ag nanocomposite coatings as electrical contact material
- 2010
-
Ingår i: Proceedings of the 56th IEEE Holm Conference on Electrical Contacts (HOLM). - : IEEE. - 9781424481743 ; , s. 288-294
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This paper is a brief review of our recent work and a follow up study on nanocomposite coatings comprising nanocrystalline TiC embedded in an amorphous SiC matrix (nc-TiC/a-SiC) with and without Ag additions applied as electrical contacts. These coating materials are deposited at very high deposition rates (>10 μm/h), to meet industrial demands of high productivity. Here we consider Ti-Si-C-Ag nanocomposite coatings with Ag content in the range of 0-22 at.% deposited in a pilot-plant or an industrial deposition system by dc magnetron sputtering from compound targets onto Si(100) and SiO2(100) substrates. The microstructure, electrical, and mechanical properties of the coatings were studied with transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, electrical contact resistance, resistivity, and nanoindentation measurements. Varying the deposition parameters bias and pressure within ranges typical of coating processing had no effect on the structure. A variation was, however, observed for the contact resistance, that was determined to be in the range 400-900 mΩ at a contact force between 1.9-2.65 N. The coatings with highest Ag content had the lowest contactresistance.
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| 28. |
- Mockuté, Aurelija, et al.
(författare)
-
Age hardening in (Ti1-xAlx)B2+Delta thin films
- 2017
-
Ingår i: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 127, s. 122-126
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of (Ti0.71Al0.29)B2+1.08 have been deposited by magnetron sputtering. Post-deposition annealing at 1000 degrees C for 1 h results in increased hardness and elastic modulus, from 32 to 37 GPa and from 436 to 461 GPa, respectively. In both as-deposited and annealed states the films adhere well to the substrate, indicating no considerable internal stress. The initial high hardness is attributed to a columnar microstructure consisting of crystalline (Ti,Al)B-2 columns separated by an amorphous B matrix. The observed age hardening corresponds to phase separation within the (Ti,Al)B-2 columns including the formation of Ti-deficient crystallites within the grain interior upon annealing.
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| 29. |
- Mockuté, Aurelija, et al.
(författare)
-
Synthesis and characterization of (Ti1-xAlx)B2+Delta thin films from combinatorial magnetron sputtering
- 2019
-
Ingår i: Thin Solid Films. - : ELSEVIER SCIENCE SA. - 0040-6090 .- 1879-2731. ; 669, s. 181-187
-
Tidskriftsartikel (refereegranskat)abstract
- (Ti1-xAlx)B2+Delta films with a lateral composition gradient of x = [0.30-0.66] and Delta = [0.07-1.22] were deposited on an Al2O3 wafer by dual magnetron sputtering at 400 degrees C from sintered TiB2 and AlB2 targets. Composition analysis indicates that higher Ti:Al ratios favor overstoichiometry in B and a reduced incorporation of O. Transmission electron microscopy reveals distinctly different microstructures of Ti- and Al-rich compositions, with formation of characteristic conical growth features for the latter along with a lower degree of crystallinity and significantly less tissue phase from B segregation at the grain boundaries. For Al-rich films, phase separation into Ti- and Al-rich diboride nanometer-size domains is observed and interpreted as surface-initiated spinodal decomposition. The hardness of the films ranges from 14 to 28 GPa, where the higher values were obtained for the Ti-rich regions of the metal boride.
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| 30. |
- Molin, Jonas, 1972-
(författare)
-
Business Streamlining : Toward a Substantive Theory of the Streamlining of Outsourced Business Processes
- 2014
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Research comparing public-private services outsourcing applying a longitudinal approach including the production/delivery processes (life after purchase) in services sourcing contexts is scarce. In addition, prior studies on service sourcing tend be under conceptualized.To address the above this licentiate thesis presents the results of a comparative and grounded theory inspired case study of two major Swedish FM services outsourcing projects, a public and a private case of operational partnering. Client-provider interaction processes on management level have been followed regularly over time utilizing participant observation as a core element combined with interviews and documentary studies. Observed variations in relational orientation over time, are problematized and discussed. A substantive theory – Business streamlining - of Facility Management outsourcing processes, including the seldom-researched life after purchase processes, is outlined and contextualized. It is argued that existing relational classifications, such as operational partnering, do not capture the life after purchase dynamics of the studied relationships. Business streamlining rests on four main categories, which have major influence on how Facility Management relationships evolve over time.
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| 31. |
- Mühlbacher, Marlene, 1987-
(författare)
-
High-resolution characterization of TiN diffusion barrier layers
- 2015
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Titanium nitride (TiN) films are widely applied as diffusion barrier layers in microelectronic devices. The continued miniaturization of such devices not only poses new challenges to material systems design, but also puts high demands on characterization techniques. To gain understanding of diffusion processes that can eventually lead to failure of the barrier layer and thus of the whole device, it is essential to develop routines to chemically and structurally investigate these layers down to the atomic scale. In the present study, model TiN diffusion barriers with a Cu overlayer acting as the diffusion source were grown by reactive magnetron sputtering on MgO(001) and thermally oxidized Si(001) substrates. Cross-sectional transmission electron microscopy (XTEM) of the pristine samples revealed epitaxial, single-crystalline growth of TiN on MgO(001), while the polycrystalline TiN grown on Si(001) exhibited a [001]-oriented columnar microstructure. Various annealing treatments were carried out to induce diffusion of Cu into the TiN layer. Subsequently, XTEM images were recorded with a high-angle annular dark field detector, which provides strong elemental contrast, to illuminate the correlation between the structure and the barrier efficiency of the single- and polycrystalline TiN layers. Particular regions of interest were investigated more closely by energy dispersive X-ray (EDX) mapping. These investigations are completed by atom probe tomography (APT) studies, which provide a three-dimensional insight into the elemental distribution at the near-interface region with atomic chemical resolution and high sensitivity. In case of the single-crystalline barrier, a uniform Cu-enriched diffusion layer of 12 nm could be detected at the interface after an annealing treatment at 1000 °C for 12 h. This excellent barrier performance can be attributed to the lack of fast diffusion paths such as grain boundaries. Moreover, density-functional theory calculations predict a stoichiometry-dependent atomic diffusion mechanism of Cu in bulk TiN, with Cu diffusing on the N-sublattice for the experimental N/Ti ratio. In comparison, the polycrystalline TiN layers exhibited grain boundaries reaching from the Cu-TiN interface to the substrate, thus providing direct diffusion paths for Cu. However, the microstructure of these columnar layers was still dense without open porosity or voids, so that the onset of grain boundary diffusion could only be found after annealing at 900 °C for 1 h.The present study shows how to combine two high resolution state-of-the-art methods, TEM and APT, to characterize model TiN diffusion barriers. It is shown how to correlate the microstructure with the performance of the barrier layer by two-dimensional EDX mapping and three-dimensional APT. Highly effective Cu-diffusion barrier function is thus demonstrated for single-crystal TiN(001) (up to 1000 °C) and dense polycrystalline TiN (900 °C).
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| 32. |
- Rogström, Lina, et al.
(författare)
-
Age hardening in arc-evaporated ZrAlN thin films
- 2010
-
Ingår i: Scripta Materialia. - Amsterdam : Elsevier Science B.V.. - 1359-6462 .- 1872-8456. ; 62:10, s. 739-741
-
Tidskriftsartikel (refereegranskat)abstract
- Zr0.44Al0.56N1.20 films were deposited by reactive arc evaporation on WC-Co substrates. As-deposited films have a defect-rich NaCl-cubic and wurtzite phase mixture. During annealing at 1100 degrees C the films undergo simultaneous recovery of the ZrN-rich c-ZrAlN nanoscale domains and formation of semicoherent w-ZrAlN nanobricks, while the excess nitrogen is released. This process results in an age hardening effect as high as 36%, as determined by nanoindentation. At 1200 degrees C, the w-AlN recrystallizes and the hardening effect is lost.
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| 33. |
- Rogström, Lina, et al.
(författare)
-
Thermal stability and mechanical properties of arc evaporated ZrN/ZrAlN multilayers
- 2010
-
Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090 .- 1879-2731. ; 519:2, s. 694-699
-
Tidskriftsartikel (refereegranskat)abstract
- ZrN1.20/Zr0.44Al0.56N1.20 multilayer films as well as ZrN1.17 and Zr0.44Al0.56N1.20 films were deposited by reactive arc evaporation on WC–Co substrates. Samples were post-deposition annealed for 2 h at 800–1200 °C. As-deposited and heat treated films were characterized by scanning transmission electron microscopy, X-ray diffraction and nanoindentation. The thermal stability was studied using a combination of differential scanning calorimetry, thermogravimetry, and mass spectrometry. The as-deposited Zr0.44Al0.56N1.20 film exhibits a nanocomposite structure of cubic and wurtzite ZrAlN. During annealing, the formation of ZrN- and AlN-rich domains results in age hardening of both the Zr0.44Al0.56N1.20 and the ZrN/ZrAlN multilayers. The age hardening is enhanced in the ZrN/ZrAlN multilayer due to straining of the ZrAlN sublayers in which a maximum hardness of 31 GPa is obtained after annealing at 1100 °C.
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| 34. |
- Tengstrand, Olof, et al.
(författare)
-
Structure and electrical properties of Nb-Ge-C nanocomposite coatings
- 2014
-
Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 32:4, s. 041509-
-
Tidskriftsartikel (refereegranskat)abstract
- Nb-Ge-C nanocomposite thin films were deposited by dc magnetron sputtering using three elemental targets. The films consist of substoichiometric NbCx in a nanometer-thick matrix of amorphous C and Ge. Films with no Ge contain grains that are elongated in the growth direction with a (111) preferred crystallographic orientation. With the addition of similar to 12 at. % Ge, the grains are more equiaxed and exhibit a more random orientation. At even higher Ge contents, the structure also becomes denser. The porous structure of the low Ge content films result in O uptake from the ambient. With higher C content in the films both the amount of amorphous C and C/Nb-ratio increases. The contact resistance was measured by four-point technique as a function of contact force between 0 and 10 N. The lowest contact resistance (1.7 m Omega) is obtained at 10 N. The resistivity varies between 470 and 1700 mu Omega center dot cm depending on porosity and O content.
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| 35. |
- Tucker, Mark, et al.
(författare)
-
Filtered pulsed cathodic arc deposition of fullerene-like carbon and carbon nitride films
- 2014
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 115:14, s. 144312-
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon and carbon nitride films (CNx , 0 ≤ x ≤ 0.26) were deposited by filtered pulsed cathodic arc and were investigated using transmission electron microscopy and X-ray photoelectron spectroscopy. A “fullerene-like” (FL) structure of ordered graphitic planes, similar to that of magnetron sputtered FL-CNx films, was observed in films deposited at 175 °C and above, with N2 pressures of 0 and 0.5 mTorr. Higher substrate temperatures and significant nitrogen incorporation are required to produce similar FL structure by sputtering, which may, at least in part, be explained by the high ion charge states and ion energies characteristic of arc deposition. A gradual transition from majority sp3-hybridized films to sp2 films was observed with increasing substrate temperature. High elastic recovery, an attractive characteristic mechanical property of FL-CNx films, is evident in arc-deposited films both with and without nitrogen content, and both with and without FL structure.
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| 36. |
- Abbasi, Mazhar Ali, et al.
(författare)
-
Decoration of ZnO nanorods with coral reefs like NiO nanostructures by the hydrothermal growth method and their luminescence study
- 2014
-
Ingår i: Materials. - : MDPI. - 1996-1944. ; 7:1, s. 430-440
-
Tidskriftsartikel (refereegranskat)abstract
- Composite nanostructures of coral reefs like p-type NiO on n-type ZnO nanorods have been decorate on fluorine-doped tin oxide glass substrates by the hydrothermal growth. Structural characterization was performed by field emission scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction techniques. This investigation has shown that the adopted synthesis has led to high crystalline quality nanostructures. Morphological study shows that the coral reefs like nanostructures are densely packed on the ZnO nanorods. Cathodoluminescence (CL) spectra for the synthesized composite nanostructures were dominated by a near band gap emission at 380 nm and by a broad interstitial defect related luminescence centered at ~630 nm. Spatially resolved CL images reveal that the luminescence originates mainly from the ZnO nanorods.
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| 37. |
- Abom, A.E., et al.
(författare)
-
Characterization of the metal-insulator interface of field-effect chemical sensors
- 2003
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:12, s. 9760-9768
-
Tidskriftsartikel (refereegranskat)abstract
- The metal-insulator interface of hydrogen-sensitive metal-insulator-semiconductor capacitors, with SiO2 as the insulator and Pt as the metal contact, was discussed. It was found that the difference in hydrogen response between differently prepared devices was explained by a difference in concentration of available adsorption sites. The analysis showed that the concentration of Pt atoms in contact with the oxide affected both the hydrogen response and the metal-oxide adhesion.
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| 38. |
- Abom, A.E., et al.
(författare)
-
Experimental evidence for a dissociation mechanism in NH3 detection with MIS field-effect devices
- 2003
-
Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 89:1-2
-
Tidskriftsartikel (refereegranskat)abstract
- The gas response mechanism of ammonia detection with Pt-based metal-insulator-semiconductor (MIS) field-effect sensors was investigated. An experimental model system was designed which compares the responses of thick continuous Pt layers with controlled morphology and surface chemical composition, with the response of thin, discontinuous layers. The surface of a thick, continuous sputter-deposited Pt film is modified, either by (i) the deposition of a thin SiO2 overlayer, (ii) reactive sputter deposition of PtOx, or (iii) co-deposition of Pt with SiO2 in Ar + O2 atmospheres. We show that the ammonia response is caused by the formation of atomic hydrogen through the dissociation of NH3 at temperatures <200 °C. It is found that the modified surfaces exhibit increased ammonia selectivity compared to a pure Pt film. Results from this work indicate that the reason for the changed selectivity is the appearance of an oxidized PtOx phase or triple phase boundaries between Pt, SiO2 and the ambient gas, rather than for solely morphological reasons. © 2002 Elsevier Science B.V. All rights reserved.
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| 39. |
- Abom, A.E., et al.
(författare)
-
Influence of gate metal film growth parameters on the properties of gas sensitive field-effect devices
- 2002
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 409:2, s. 233-242
-
Tidskriftsartikel (refereegranskat)abstract
- Thin films of Pt have been grown as gate metals on the oxide surface of gas sensitive field-effect devices. Both electron beam evaporation and dc magnetron sputtering has been used. The energy of the impinging Pt atoms, the substrate temperature and the thickness of the Pt film were used as parameters in this study. The influence of the growth parameters on the gas response has been investigated and compared with the properties of the films, studied by transmission electron microscopy, Auger electron spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction. The conditions during growth of the Pt film are found to have a large impact on the properties of the device. As expected, crystallinity, morphology and the metal/substrate interfacial structure are also affected by processing parameters. Three different growth processes stand out as the most promising from gas sensor considerations, namely room temperature evaporation, sputtering at high pressures and sputtering at high temperatures. The correlation between gas responses and properties of the gas sensitive layer is discussed. © 2002 Elsevier Science B.V. All rights reserved.
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| 40. |
- Abom, A.E., et al.
(författare)
-
Thin oxide films as surface modifiers of MIS field effect gas sensors
- 2002
-
Ingår i: Sensors and actuators. B, Chemical. - 0925-4005 .- 1873-3077. ; 85:1-2, s. 109-119
-
Tidskriftsartikel (refereegranskat)abstract
- The catalytic activity at the surface of Pt based MIS field effect gas sensors is modified by the deposition of thin films of SnO2, Al2O3 and SiO2, grown by reactive sputtering. It is found that a very thin layer (<10 nm) of SiO2 and SnO2 changes the catalytic activity towards higher NH3 selectivity, but with thicker films the sensor response vanishes. Since the response mechanism for these sensors is dependent on dissociation of molecules, it is likely that at low temperatures (140 °C), neither dissociation on nor transport/diffusion through the thicker films takes place. However, with Pt in conjunction with SiO2 or SnO2, the surface reactions will be altered, with enhanced NH3 selectivity as a result. A thin film of Al2O3, on the other hand, has a much smaller influence on the gas response to the test gases used in this work. Furthermore the sputtering process is found to strongly influence the sensor responses, and specifically reduce the sensitivity of the sensor. A thin intermediate layer of evaporated Pt does not completely protect the underlying structure from sputter induced damage. © 2002 Elsevier Science B.V. All rights reserved.
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| 41. |
- Abrikosov, Igor, et al.
(författare)
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Phase Stability and Elasticity of TiAlN
- 2011
-
Ingår i: Materials. - : MDPI. - 1996-1944. ; 4:9, s. 1599-1618
-
Tidskriftsartikel (refereegranskat)abstract
- We review results of recent combined theoretical and experimental studies of Ti1−xAlxN, an archetypical alloy system material for hard-coating applications. Theoretical simulations of lattice parameters, mixing enthalpies, and elastic properties are presented. Calculated phase diagrams at ambient pressure, as well as at pressure of 10 GPa, show a wide miscibility gap and broad region of compositions and temperatures where the spinodal decomposition takes place. The strong dependence of the elastic properties and sound wave anisotropy on the Al-content offers detailed understanding of the spinodal decomposition and age hardening in Ti1−xAlxN alloy films and multilayers. TiAlN/TiN multilayers can further improve the hardness and thermal stability compared to TiAlN since they offer means to influence the kinetics of the favorable spinodal decomposition and suppress the detrimental transformation to w-AlN. Here, we show that a 100 degree improvement in terms of w-AlN suppression can be achieved, which is of importance when the coating is used as a protective coating on metal cutting inserts.
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| 42. |
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| 43. |
- Adamovic, Dragan, et al.
(författare)
-
Enhanced intra- and interlayer mass transport on Pt(111) via 5 - 50 eV Pt atom impacts on two-dimensional Pt clusters
- 2006
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:4, s. 2235-2243
-
Tidskriftsartikel (refereegranskat)abstract
- Embedded-atom molecular dynamics simulations were used to investigate the effects of low-energy (5–50 eV) normally-incident self-ion irradiation of two-dimensional compact Pt3, Pt7, Pt19, and Pt37 clusters on Pt(111). We follow atomistic pathways leading to bombardment-induced intra- and interlayer mass transport. The results can be described in terms of three impact energy regimes. With E ≤ 20 eV, we observe an increase in 2D island dimensions and negligible residual point defect formation. As the impact energy is raised above 20 eV, we observe an increase in irradiation-induced lateral mass transport, a decrease in island size, and the activation of interlayer processes. For E ≥ 35 eV, this trend continues, but point defects, in the form of surface vacancies, are also formed. The results illustrate the richness of the dynamical interaction mechanisms occurring among incident energetic species, target clusters, and substrate atoms, leading to island preservation, reconfiguration, disruption and/or residual point defects formation. We discuss the significance of these results in terms of thin film growth.
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| 44. |
- Adamovic, Dragan, 1973-, et al.
(författare)
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Kinetic pathways leading to layer-by-layer growth from hyperthermal atoms : A Multibillion time step molecular dynamics study
- 2007
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 76, s. 115418-115425
-
Tidskriftsartikel (refereegranskat)abstract
- We employ multibillion time step embedded-atom molecular dynamics simulations to investigate the homoepitaxial growth of Pt(111) from hyperthermal Pt atoms (EPt=0.2–50eV) using deposition fluxes approaching experimental conditions. Calculated antiphase diffraction intensity oscillations, based on adatom coverages as a function of time, reveal a transition from a three-dimensional multilayer growth mode with EPt<20eV to a layer-by-layer growth with EPt≥20eV. We isolate the effects of irradiation-induced processes and thermally activated mass transport during deposition in order to identify the mechanisms responsible for promoting layer-by-layer growth. Direct evidence is provided to show that the observed transition in growth modes is primarily due to irradiation-induced processes which occur during the 10ps following the arrival of each hyperthermal atom. The kinetic pathways leading to the transition involve both enhanced intralayer and interlayer adatom transport, direct incorporation of energetic atoms into clusters, and cluster disruption leading to increased terrace supersaturation.
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| 45. |
- Adamovic, Dragan, et al.
(författare)
-
Low-energy ion irradiation during film growth: Kinetic pathways leading to enhanced adatom migration rates
- 2005
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 86, s. 211915-
-
Tidskriftsartikel (refereegranskat)abstract
- Embedded-atom molecular dynamics simulations are used to investigate the effects of low-energy self-ion irradiation of Pt adatoms on Pt(111). Here, we concentrate on self-bombardment dynamics, i.e., isolating and monitoring the atomic processes, induced by normally incident Pt atoms with energies E ranging from 5 to 50 eV, that can affect intra- and interlayer mass transport.. We find that adatom scattering, surface channeling, and dimer formation occur at all energies. Atomic intermixing events involving incident and terrace atoms are observed at energies 15 eV, while the collateral formation of residual surface vacancies is observed only with E>40 eV. The overall effect of low-energy self-ion irradiation is to enhance lateral adatom and terrace atom migration. ©2005 American Institute of Physics
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| 46. |
- Alami, Jones, et al.
(författare)
-
High-power impulse magnetron sputtering of Ti-Si-C thin films from a Ti3SiC2 compound target
- 2006
-
Ingår i: Thin Solid Films. - : Institutionen för fysik, kemi och biologi. - 0040-6090 .- 1879-2731. ; 515:4, s. 1731-1736
-
Tidskriftsartikel (refereegranskat)abstract
- We have deposited Ti-Si-C thin films using high-power impulse magnetron sputtering (HIPIMS) from a Ti3SiC2 compound target. The as-deposited films were composite materials with TiC as the main crystalline constituent. X-ray diffraction and photoelectron spectroscopy indicated that they also contained amorphous SiC, and for films deposited on inclined substrates, crystalline Ti5Si3Cx. The film morphology was dense and flat, while films deposited with dc magnetron sputtering under comparable conditions were rough and porous. Due to the high degree of ionization of the sputtered species obtained in HIPIMS, it is possible to control the film composition, in particular the C content, by tuning the substrate inclination angle, the Ar process pressure, and the bias voltage.
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| 47. |
- Albani, Giorgia, et al.
(författare)
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Evolution in boron-based GEM detectors for diffraction measurements : From planar to 3D converters
- 2016
-
Ingår i: Measurement science and technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 27:11
-
Tidskriftsartikel (refereegranskat)abstract
- The so-called '3He-crisis' has motivated the neutron detector community to undertake an intense R&D programme in order to develop technologies alternative to standard 3He tubes and suitable for neutron detection systems in future spallation sources such as the European spallation source (ESS). Boron-based GEM (gas electron multiplier) detectors are a promising '3He-free' technology for thermal neutron detection in neutron scattering experiments. In this paper the evolution of boron-based GEM detectors from planar to 3D converters with an application in diffraction measurements is presented. The use of 3D converters coupled with GEMs allows for an optimization of the detector performances. Three different detectors were used for diffraction measurements on the INES instrument at the ISIS spallation source. The performances of the GEM-detectors are compared with those of conventional 3He tubes installed on the INES instrument. The conceptual detector with the 3D converter used in this paper reached a count rate per unit area of about 25% relative to the currently installed 3He tube. Its timing resolution is similar and the signal-to-background ratio (S/B) is 2 times lower.
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| 48. |
- Alexandrou, I, et al.
(författare)
-
HREM and EELS analysis of fullerene-like carbon films
- 1999
-
Ingår i: Institute of Physics Conference Series. - 0951-3248 .- 2154-6630. ; :161, s. 369-372
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon thin films were grown by Laser-Arc deposition and their structure and bonding were examined using High Resolution Electron Microscopy (HREM) and Electron Energy Loss Spectroscopy (EELS). Through focal series of HREM images reveal that the film consists of curved graphene sheets forming swirls and concentric rings with a diameter of 4-6 nm. The sheet spacing was determined by selected area diffraction to be 0.363 nm. Contrast transfer function calculations are used to explain why the pattern formed by the curved sheets is more evident at Gaussian focus rather than at Scherzer defocus, Although the films demonstrate high microhardness and elastic recovery, qualitative assessment of the EELS spectra reveals that the film consists primarily of sp(2) hybridised carbon. A model is proposed to describe how such a material made of graphene sheets can exhibit such remarkable mechanical properties.
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| 49. |
- Alling, Björn, et al.
(författare)
-
A theoretical investigation of mixing thermodynamics, age-hardening potential, and electronic structure of ternary (M1-xMxB2)-M-1-B-2 alloys with AlB2 type structure
- 2015
-
Ingår i: Scientific Reports. - : Nature Publishing Group: Open Access Journals - Option C / Nature Publishing Group. - 2045-2322. ; 5
-
Tidskriftsartikel (refereegranskat)abstract
- Transition metal diborides are ceramic materials with potential applications as hard protective thin films and electrical contact materials. We investigate the possibility to obtain age hardening through isostructural clustering, including spinodal decomposition, or ordering-induced precipitation in ternary diboride alloys. By means of first-principles mixing thermodynamics calculations, 45 ternary (M1-xMxB2)-M-1-B-2 alloys comprising (MB2)-B-i (M-i = Mg, Al, Sc, Y, Ti, Zr, Hf, V, Nb, Ta) with AlB2 type structure are studied. In particular Al1-xTixB2 is found to be of interest for coherent isostructural decomposition with a strong driving force for phase separation, while having almost concentration independent a and c lattice parameters. The results are explained by revealing the nature of the electronic structure in these alloys, and in particular, the origin of the pseudogap at E-F in TiB2, ZrB2, and HfB2.
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| 50. |
- Alling, Björn, 1980-, et al.
(författare)
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A unified cluster expansion method applied to the configurational thermodynamics of cubic TiAlN
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 83:10, s. 104203-
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Tidskriftsartikel (refereegranskat)abstract
- We use a study of the cubic Ti1−xAlxN system to illustrate a practical way of combining the major methodologies within alloy theory, the Connolly-Williams cluster expansion and the generalized perturbation method, in order to solve difficult alloy problems. The configurational, concentration dependent, Hamiltonian is separated into a fixed-lattice and a local lattice relaxation part. The effective cluster interactions of the first part is obtained primarily with a GPM-based approach while the later is obtained using cluster expansion. In our case the impact on the isostructural phase diagram of considering short range clustering beyond the mean field approximation, obtained from the mixing enthalpy and entropy of the random alloy, is rather small, especially in the composition region x ≤ 0.66, within reach of thin film growth techniques.
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