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41.
  • Greczynski, Grzegorz, et al. (författare)
  • Core-level spectra and binding energies of transition metal nitrides by non-destructive x-ray photoelectron spectroscopy through capping layers
  • 2017
  • Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 396, s. 347-358
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first measurements of x-ray photoelectron spectroscopy (XPS) core level binding energies (BE: s) for the widely-applicable group IVb-VIb polycrystalline transition metal nitrides (TMN's) TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN, and WN as well as AlN and SiN, which are common components in the TMN-based alloy systems. Nitride thin film samples were grown at 400.degrees C by reactive dc magnetron sputtering from elemental targets in Ar/ N-2 atmosphere. For XPS measurements, layers are either (i) Ar+ ion-etched to remove surface oxides resulting from the air exposure during sample transfer from the growth chamber into the XPS system, or (ii) in situ capped with a few nm thick Cr or W overlayers in the deposition system prior to air-exposure and loading into the XPS instrument. Film elemental composition and phase content is thoroughly characterized with time-of-flight elastic recoil detection analysis (ToF(-) ERDA), Rutherford backscattering spectrometry (RBS), and x-ray diffraction. High energy resolution core level XPS spectra acquired with monochromatic Al K alpha radiation on the ISO-calibrated instrument reveal that even mild etching conditions result in the formation of a nitrogen-deficient surface layer that substantially affects the extracted binding energy values. These spectra-modifying effects of Ar+ ion bombardment increase with increasing the metal atom mass due to an increasing nitrogen-to-metal sputter yield ratio. The superior quality of the XPS spectra obtained in a non-destructive way from capped TMN films is evident from that numerous metal peaks, including Ti 2p, V 2p, Zr 3d, and Hf 4f, exhibit pronounced satellite features, in agreement with previously published spectra from layers grown and analyzed in situ. In addition, the N/ metal concentration ratios are found to be 25-90% higher than those obtained from the corresponding ion-etched surfaces, and in most cases agree very well with the RBS and ToF-E ERDA values. The N 1 s BE: s extracted from capped TMN films, thus characteristic of a native surface, show a systematic trend, which contrasts with the large BE spread of literature "reference" values. Hence, non-destructive core level XPS employing capping layers provides an opportunity to obtain high-quality spectra, characteristic of virgin in situ grown and analyzed TMN films, although with larger versatility, and allows for extracting core level BE values that are more reliable than those obtained from sputter-cleaned N-deficient surfaces. Results presented here, recorded from a consistent set of binary TMN's grown under the same conditions and analyzed in the same instrument, provide a useful reference for future XPS studies of multinary materials systems allowing for true deconvolution of complex core level spectra.
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42.
  • Greczynski, Grzegorz, 1973-, et al. (författare)
  • Reference binding energies of transition metal carbides by core-level x-ray photoelectron spectroscopy free from Ar+ etching artefacts
  • 2018
  • Ingår i: Applied Surface Science. - : ELSEVIER SCIENCE BV. - 0169-4332 .- 1873-5584. ; 436, s. 102-110
  • Tidskriftsartikel (refereegranskat)abstract
    • We report x-ray photoelectron spectroscopy (XPS) core level binding energies (BE's) for the widely-applicable groups IVb-VIb transition metal carbides (TMCs) TiC, VC, CrC, ZrC, NbC, MoC, HfC, TaC, and WC. Thin film samples are grown in the same deposition system, by dc magnetron co-sputtering from graphite and respective elemental metal targets in Ar atmosphere. To remove surface contaminations resulting from exposure to air during sample transfer from the growth chamber into the XPS system, layers are either (i) Ar+ ion-etched or (ii) UHV-annealed in situ prior to XPS analyses. High resolution XPS spectra reveal that even gentle etching affects the shape of core level signals, as well as BE values, which are systematically offset by 0.2-0.5 eV towards lower BE. These destructive effects of Ar+ ion etch become more pronounced with increasing the metal atom mass due to an increasing carbon-to-metal sputter yield ratio. Systematic analysis reveals that for each row in the periodic table (3d, 4d, and 5d) C 1s BE increases from left to right indicative of a decreased charge transfer from TM to C atoms, hence bond weakening. Moreover, C 1s BE decreases linearly with increasing carbide/metal melting point ratio. Spectra reported here, acquired from a consistent set of samples in the same instrument, should serve as a reference for true deconvolution of complex XPS cases, including multinary carbides, nitrides, and carbonitrides.
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43.
  • Greczynski, Grzegorz, et al. (författare)
  • Unprecedented Al supersaturation in single-phase rock salt structure VAlN films by Al+ subplantation
  • 2017
  • Ingår i: Journal of Applied Physics. - : AMER INST PHYSICS. - 0021-8979 .- 1089-7550. ; 121:17
  • Tidskriftsartikel (refereegranskat)abstract
    • Modern applications of refractory ceramic thin films, predominantly as wear-protective coatings on cutting tools and on components utilized in automotive engines, require a combination of excellent mechanical properties, thermal stability, and oxidation resistance. Conventional design approaches for transition metal nitride coatings with improved thermal and chemical stability are based on alloying with Al. It is well known that the solubility of Al in NaCl-structure transition metal nitrides is limited. Hence, the great challenge is to increase the Al concentration substantially while avoiding precipitation of the thermodynamically favored wurtzite-AlN phase, which is detrimental to mechanical properties. Here, we use VAlN as a model system to illustrate a new concept for the synthesis of metastable single-phase NaCl-structure thin films with the Al content far beyond solubility limits obtained with conventional plasma processes. This supersaturation is achieved by separating the film-forming species in time and energy domains through synchronization of the 70-mu s-long pulsed substrate bias with intense periodic fluxes of energetic Al+ metal ions during reactive hybrid high power impulse magnetron sputtering of the Al target and direct current magnetron sputtering of the V target in the Ar/N-2 gas mixture. Hereby, Al is subplanted into the cubic VN grains formed by the continuous flux of low-energy V neutrals. We show that Al subplantation enables an unprecedented 42% increase in metastable Al solubility limit in V1-xAlxN, from x-0.52 obtained with the conventional method to 0.75. The elastic modulus is 325 +/- 5GPa, in excellent agreement with density functional theory calculations, and approximately 50% higher than for corresponding films grown by dc magnetron sputtering. The extension of the presented strategy to other Al-ion-assisted vapor deposition methods or materials systems is straightforward, which opens up the way for producing supersaturated single-phase functional ceramic alloy thin films combining excellent mechanical properties with high oxidation resistance. Published by AIP Publishing.
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44.
  • Greczynski, Grzegorz, et al. (författare)
  • X-ray photoelectron spectroscopy of thin films
  • 2023
  • Ingår i: NATURE REVIEWS METHODS PRIMERS. - : SPRINGERNATURE. - 2662-8449. ; 3:1
  • Tidskriftsartikel (refereegranskat)abstract
    • X-ray photoelectron spectroscopy (XPS) is a popular analytical technique in materials science as it can assess the surface chemistry of a broad range of samples. This Primer concerns best practice in XPS analysis, aimed at both entry-level and advanced users, with a focus on thin film samples synthesized under vacuum conditions. The high surface to volume ratio of thin films means that factors such as substrate choice and air exposure time are important for the final result. Essential concepts are introduced, such as binding energy, photoelectric effect, spectral referencing and chemical shift, as well as practical aspects including surface sensitivity, probing depth, energy resolution, sample handling and sputter etching. Correct procedures for experimental planning, instrument set-up, sample preparation, data acquisition, results analysis and presentation are reviewed in connection with physical principles and common applications. Typical problems, including charging, spectral overlap, sputter damage and binding energy referencing, are discussed along with possible solutions or workarounds. Finally, a workflow is presented for arriving at high-quality results. X-ray photoelectron spectroscopy (XPS) can be used to investigate chemical bonding and elemental composition. This Primer discusses how XPS can be used to characterize thin films, including key considerations for sample preparation, experimental set-up and data analysis.
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45.
  • Gunnarsson Sarius, Niklas, et al. (författare)
  • Electrochemically based low-cost high precision processing in MOEMS packaging
  • 2009
  • Ingår i: Electrochimica Acta. - : Elsevier BV. - 0013-4686 .- 1873-3859. ; 54:9, s. 2458-2465
  • Tidskriftsartikel (refereegranskat)abstract
    • Precision processing in MOEMS (micro-opto-electromechanical systems) packaging has been studied based on electrochemical processes with the purpose of establishing technology for low-cost multifunctional encapsulation of microsystems and assembly of opto-electric access links in polymer. The electrochemically based processes studied in this paper include: 1. Electroforming of a polymer moulding tool (stamper) in a nickel sulphamate electrolyte on a highprecision 3D etched silicon template. 2. Patterning of 3D surfaces by an electrophoretic photoresist. 3. Precision plating of Au and Sn for self-alignment of chips by eutectic Au-Sn solder. The results show that nickel stampers with adequately low internal stress can be electroformed on 3D silicon wafers. Furthermore, 3D polymer samples manufactured by the nickel stampers can be patterned with metal lines down to 20 mu m width using electrophoretic photoresist. Finally, eutectic Au-Sn solder bumps are realized by electroplating of Au and Sn followed by reflowing, satisfying the demands on dimension and alloy composition control over a 4 in. Si wafer.
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46.
  • Gunnarsson Sarius, Niklas, 1976- (författare)
  • Surface Technology for Optical and Electrical Connectors
  • 2010
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis treats surface engineering with the purpose of improved quality of optical and electricalconnectors with a focus on electroplated and magnetron sputtered materials. In electroforming of tools formanufacturing optical connectors, the influence of ultrasonic agitation on intrinsic stresses and fillingproperties of electroplated Ni has been studied. It is established that the ultrasonic agitation at the substratesurface during deposition impacts the intrinsic stresses making it possible to increase deposition rate viacurrent density, with stress-free or low-stress levels in the Ni layers. Reduced variations of the intrinsicstress over the surface with the current density is a further important result. Filling of grooves byelectroplating of Ni using ultrasonic agitation is demonstrated. This is due to increasing mass transport ofspecies into the grooves compared to conventional pumped agitation. The enhanced filling propertiesmakes it possible to electroplate Ni in the bottom of high-aspect-ratio grooves. In order to industriallyimplement new nanocomposite coatings on electronic connectors, studies have been performed regardingthe thermal diffusion barrier properties against Cu for Ti-Si-C and Ti-Si-C-Ag nanocomposites, depositeddirectly onto Cu substrates or with sputtered Ni, Ti or electroplated Ni as an intermediate coating. Theapplication of an electroplated Ni diffusion barrier coating, hinders Cu from reaching the surface of thenanocomposites. Also, Ti-Si-C-Ag nanocomposite deposited on magnetron sputtered Ni or Ti on Cusubstrates hinder Cu from diffusing to the surface after annealing. The contact resistance of Ag-Pdtopcoated Ti-Si-C-Ag-Pd and Ti-Si-C-Ag nanocomposite coatings in contact with hard gold is shown tocompete with hard gold in contact with itself, as electrical contact coatings at contact forces around 5 N.Ag-Pd topcoated Ti-Si-C-Ag-Pd in contact with hard gold is shown to have approximately the same contactresistance as hard gold in contact with hard gold at contact forces around 0.1 N, which here is in the 10 mΩrange, while Ti-Si-C-Ag nanocomposite coatings in contact with hard gold has a contact resistance that isup to 10 times higher. The overall contribution of this thesis can be summarised as a deeper knowledge andunderstanding of techniques and coatings, that help reduce cost and increase reliability of electronics.
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47.
  • Hellgren, Niklas, et al. (författare)
  • High-power impulse magnetron sputter deposition of TiBx thin films : Effects of pressure and growth temperature
  • 2019
  • Ingår i: Vacuum. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0042-207X .- 1879-2715. ; 169
  • Tidskriftsartikel (refereegranskat)abstract
    • Titanium boride, TiBx thin films are grown in pure Ar discharges by high-power impulse magnetron sputtering (HiPIMS) from a compound TiB2 target Film compositions are determined by time-of-flight elastic recoil detection analysis and Rutherford backscattering spectrometry as a function of deposition temperature (T-s = 25-900 degrees C) and Ar pressure (p(Ar) = 0.67-2.67 Pa, 5-20 mTorr). For reference, films are also grown by direct current magnetron sputtering (dcMS) under similar conditions. The HiPIMS waveform, average target power P-T, and resulting film compositions are strongly dependent not only on P-Ar, but also on T-s. At high pressures the effect of varying T-s on P-T is minimal, while at lower P-Ar the effect of T-s is more pronounced, due to substrate-temperature-induced gas rarefaction. Films grown by HiPIMS at 0.67 Pa are understoichiometric, with B/Ti = 1.4-1.5, while at 2.67 Pa, B/Ti decreases from 2.4 to 1.4 as T-s increases from 25 to 900 degrees C. dcMS-deposited films are overstoichiometric (B/Ti similar or equal to 3) when grown at low pressures, and near-stoichiometric (B/Ti similar or equal to r 1.9-2.2) for higher P-Ar. All experimental results are explained by differences in the ionization potentials of sputtered Ti and B atoms, together with P-Ar- and T-s-dependent gas-phase scattering.
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48.
  • Hellgren, Niklas, et al. (författare)
  • Synthesis and characterization of TiBx (1.2=x=2.8) thin films grown by DC magnetron co-sputtering from TiB2 and Ti targets
  • 2022
  • Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 433
  • Tidskriftsartikel (refereegranskat)abstract
    • Titanium boride, TiBx, thin films were grown by direct current magnetron co-sputtering from a compound TiB2 target and a Ti target at an Ar pressure of 2.2 mTorr (0.3 Pa) and substrate temperature of 450 ?degrees C. While keeping the power of the TiB2 target constant at 250 W, and by varying the power on the Ti target, P-Ti, between 0 and 100 W, the B/Ti ratio in the film could be continuously and controllably varied from 1.2 to 2.8, with close-tostoichiometric diboride films achieved for P-Ti = 50 W. This was done without altering the deposition pressure, which is otherwise the main modulator for the composition of magnetron sputtered TiBx diboride thin films. The film structure and properties of the as-deposited films were compared to those after vacuum-annealing for 2 h at 1100 ?degrees C. As-deposited films consisted of small (?50 nm) randomly oriented TiB2 crystallites, interspersed in an amorphous, sometimes porous tissue phase. Upon annealing, some of the tissue phase crystallized, but the diboride average grain size did not change noticeably. The near-stoichiometric film had the lowest resistivity, 122 mu omega cm, after annealing. Although this film had growth-induced porosity, an interconnected network of elongated crystallites provides a path for conduction. All films exhibited high hardness, in the 25-30 GPa range, where the highest value of similar to 32 GPa was obtained for the most Ti-rich film after annealing. This film had the highest density and was nano-crystalline, where dislocation propagation is interrupted by the off-stoichiometric grain boundaries.
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49.
  • Hellgren, Niklas, et al. (författare)
  • X-ray photoelectron spectroscopy analysis of TiBx (1.3 <= x <= 3.0) thin films
  • 2021
  • Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : A V S AMER INST PHYSICS. - 0734-2101 .- 1520-8559. ; 39:2
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a comprehensive analysis of titanium boride thin films by x-ray photoelectron spectroscopy (XPS). Films were grown by both direct current magnetron sputtering and high- power impulse magnetron sputtering from a compound TiB2 target in Ar discharge. By varying the deposition parameters, the film composition could be tuned over the wide range 1:3 &B/Ti &3:0, as determined by elastic recoil detection analysis and Rutherford backscattering spectrometry. By comparing spectra over this wide range of compositions, we can draw original conclusions about how to interpret XPS spectra of TiBx. By careful spectra deconvolution, the signals from Ti-Ti and B-B bonds can be resolved from those corresponding to stoichiometric TiB2. The intensities of the off-stoichiometric signals can be directly related to the B/Ti ratio of the films. Furthermore, we demonstrate a way to obtain consistent and quantum-mechanically accurate peak deconvolution of the whole Ti 2p envelope, including the plasmons, for both oxidized and sputter-cleaned samples. Due to preferential sputtering of Ti over B, the film B/Ti ratio is best determined without sputter etching of the sample surface. This allows accurate compositional determination, assuming that extensive levels of oxygen are not present in the sample. Fully dense films can be accurately quantified for at least a year after deposition, while underdense samples do not give reliable data if the O/Ti ratio on the unsputtered surface is *3:5. Titanium suboxides detected after sputter etching is further indicative of oxygen penetrating the sample, and quantification by XPS should not be trusted.
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50.
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