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1.
  • Luo, Jun, et al. (författare)
  • Surface-energy triggered phase formation and epitaxy in nanometer-thick Ni1-xPtx silicide films
  • 2010
  • Ingår i: APPLIED PHYSICS LETTERS. - 0003-6951. ; 96:3, s. 031911
  • Tidskriftsartikel (refereegranskat)abstract
    • The formation of ultrathin silicide films of Ni1-xPtx at 450-850 degrees C is reported. Without Pt (x=0) and for t(Ni)andlt; 4 nm, epitaxially aligned NiSi2-y films readily grow and exhibit extraordinary morphological stability up to 800 degrees C. For t(Ni)andgt;= 4 nm, polycrystalline NiSi films form and agglomerate at lower temperatures for thinner films. Without Ni (x=1) and for t(Pt)=1-20 nm, the annealing behavior of the resulting PtSi films follows that for the NiSi films. The results for Ni1-xPtx of other compositions support the above observations. Surface energy is discussed as the cause responsible for the distinct behavior in phase formation and morphological stability.
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2.
  • Alling, Björn, 1980-, et al. (författare)
  • Mixing and decomposition thermodynamics of c-Ti1-xAlxN from first-principles calculations
  • 2007
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 75:045123
  • Tidskriftsartikel (refereegranskat)abstract
    • Wedescribe an efficient first-principles method that can be used tocalculate mixing enthalpies of transition metal nitrides with B1 structureand substitutional disorder at the metal sublattice. The technique isbased on the density functional theory. The independent sublattice modelis suggested for the treatment of disorder-induced local lattice relaxationeffects. It supplements the description of the substitutional disorder withinthe coherent potential approximation. We demonstrate the excellent accuracy ofthe method by comparison with calculations performed by means ofthe projector augumented wave method on supercells constructed as specialquasirandom structures. At the same time, the efficiency of thetechnique allows for total energy calculations on a very finemesh of concentrations which enables a reliable calculation of thesecond concentration derivative of the alloy total energy. This isa first step towards first-principles predictions of concentrations and temperatureintervals where the alloy decomposition proceeds via the spinodal mechanism.We thus calculate electronic structure, lattice parameter, and mixing enthalpiesof the quasibinary alloy c-Ti1−xAlxN. The lattice parameter follows Vegard'slaw at low fractions of AlN but deviates increasingly withincreasing Al content. We show that the asymmetry of themixing enthalpy and its second concentration derivative is associated withsubstantial variations of the electronic structure with alloy composition. Thephase diagram is constructed within the mean-field approximation.
3.
  • Gao, Xindong, et al. (författare)
  • Epitaxy of Ultrathin NiSi2 Films with Predetermined Thickness
  • 2011
  • Ingår i: Electrochemical and solid-state letters. - 1099-0062. ; 14:7, s. H268-H270
  • Tidskriftsartikel (refereegranskat)abstract
    • This letter presents a proof-of-concept process for tunable, self-limiting growth of ultrathin epitaxial NiSi2 films on Si (100). The process starts with metal sputter-deposition, followed by wet etching and then silicidation. By ionizing a fraction of the sputtered Ni atoms and biasing the Si substrate, the amount of Ni atoms incorporated in the substrate after wet etching can be controlled. As a result, the thickness of the NiSi2 films is increased from 4.7 to 7.2 nm by changing the nominal substrate bias from 0 to 600 V. The NiSi2 films are characterized by a specific resistivity around 50 mu Omega cm.
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4.
  • Gunnarsson Sarius, Niklas, 1976-, et al. (författare)
  • Contact Resistance of Ti-Si-C-Ag and Ti-Si-C-Ag-Pd Nanocomposite Coatings
  • 2012
  • Ingår i: Journal of Electronic Materials. - 0361-5235. ; 41:3, s. 560-567
  • Tidskriftsartikel (refereegranskat)abstract
    • Ti-Si-C-Ag-Pd and Ti-Si-C-Ag nanocomposite coatings were deposited by direct-current magnetron sputtering on Cu substrates with an electroplated Ni layer. Analytical electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy show that the nanocomposites consist of TiC, Ag:Pd, and amorphous SiC. The contact resistance of these coatings against a spherical Au-Co surface was measured for applied contact forces up to 5 N. Ti-Si-C-Ag-Pd coatings with Ag:Pd top coating had ~10 times lower contact resistance at contact forces below 1 N (~10 mΩ at ~0.1 N), and 2 to 3 times lower for contact forces around 5 N (<1 mΩ at 5 N), compared with the Ti-Si-C-Ag coating.
5.
  • Lu, Jun, et al. (författare)
  • On Epitaxy of Ultrathin Ni1-xPtx Silicide Films on Si(001)
  • 2010
  • Ingår i: ELECTROCHEMICAL AND SOLID STATE LETTERS. - Electrochemical Society and Institute of Electronics Engineers. - 1099-0062. ; 13:10, s. H360-H362
  • Tidskriftsartikel (refereegranskat)abstract
    • Epitaxial Ni(Pt)Si2-y (y andlt; 1) films readily grow upon thermal treatment of 2 nm thick Ni and Ni0.96Pt0.04 films deposited on Si(001). For annealing at 500 degrees C, the films are 5.4-5.6 nm thick with 61-70 mu cm in resistivity. At 750 degrees C, the epitaxial Ni(Pt)Si2-y films become 6.1-6.2 nm thick with a resistivity of 42-44 mu cm. Structural analysis reveals twins, facet wedges, and thickness inhomogeneities in the films grown at 500 degrees C. For higher temperature, an almost defect-free NiSi2-y film with a flat and sharp interface is formed. The presence of Pt makes the aforementioned imperfections more persistent.
6.
  • Luo, Jun, et al. (författare)
  • On Different Process Schemes for MOSFETs With a Controllable NiSi-Based Metallic Source/Drain
  • 2011
  • Ingår i: IEEE Transactions on Electron Devices. - 0018-9383. ; 58:7, s. 1898-1906
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper focuses on different silicidation schemes toward a controllable NiSi-based metallic source/drain (MSD) process with restricted lateral encroachment of NiSi. These schemes include thickness control of Ni, Ni-Pt alloying, and two-step annealing. Experimental results show that all the three process schemes can give rise to effective control of lateral encroachment during Ni silicidation. By controlling t(Ni), NiSi-based MSD metal-oxide-semiconductor field-effect transistors (MOSFETs) of gate length L-G = 55 nm are readily realized on ultrathin-body silicon-on-insulator substrates with 20-nm surface Si thickness. With the aid of dopant segregation (DS) to modifying the Schottky barrier heights of NiSi, both n- and p-type MSD MOSFETs show significant performance improvement, compared to reference devices without DS.
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7.
  • Magnuson, Martin, et al. (författare)
  • Electronic structure investigation of Ti3AlC2 , Ti3SiC2 , and Ti3GeC2 by soft x-ray emission spectroscopy
  • 2005
  • Ingår i: Physical Review B Condensed Matter. - 0163-1829. ; 72:24, s. 245101
  • Tidskriftsartikel (refereegranskat)abstract
    • The electronic structures of epitaxially grown films of Ti3AlC2 , Ti3SiC2 , and Ti3GeC2 have been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured high-resolution Ti L , C K , Al L , Si L , and Ge M emission spectra are compared with ab initio density-functional theory including core-to-valence dipole matrix elements. A qualitative agreement between experiment and theory is obtained. A weak covalent Ti-Al bond is manifested by a pronounced shoulder in the Ti L emission of Ti3AlC2 . As Al is replaced with Si or Ge, the shoulder disappears. For the buried Al and Si layers, strongly hybridized spectral shapes are detected in Ti3AlC2 and Ti3SiC2 , respectively. As a result of relaxation of the crystal structure and the increased charge-transfer from Ti to C, the Ti-C bonding is strengthened. The differences between the electronic structures are discussed in relation to the bonding in the nanolaminates and the corresponding change of materials properties.
8.
  • Hultman, Lars, et al. (författare)
  • Interface structure in superhard TiN-SiN nanolaminates and nanocomposites : film growth experiments and ab initio calculations
  • 2007
  • Ingår i: Physical Review. B. - 1098-0121 (print) 1550-235x (online). ; 75:15, s. 155437
  • Tidskriftsartikel (refereegranskat)abstract
    • Nanostructured materials—the subject of much of contemporary materials research—are defined by internal interfaces, the nature of which is largely unknown. Yet, the interfaces determine the properties of nanocomposites and nanolaminates. An example is nanocomposites with extreme hardness<img src="http://scitation.aip.org/stockgif3/ges.gif" />70–90  GPa, which is of the order of, or higher than, diamond. The Ti-Si-N system, in particular, is attracting attention for the synthesis of such superhard materials. In this case, the nanocomposite structure consists of TiN nanocrystallites encapsulated in a fully percolated SiNx “tissue phase” (1 to 2 monolayers thick) that is assumed to be amorphous. Here, we show that the interfacial tissue phase can be crystalline, and even epitaxial with complex surface reconstructions. Using in situ structural analyses combined with ab initio calculations, we find that SiNx layers grow epitaxially, giving rise to strong interfacial bonding, on both TiN(001) and TiN(111) surfaces. In addition, TiN overlayers grow epitaxially on SiNx/TiN(001) bilayers in nanolaminate structures. These results provide insight into the development of design rules for new nanostructured materials.
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9.
  • Berlind, Torun, 1965-, et al. (författare)
  • Protein adsorption on thin films of carbon and carbon nitride monitored with in situ ellipsometry
  • 2011
  • Ingår i: ACTA BIOMATERIALIA. - Elsevier Science B.V. Amsterdam. - 1742-7061. ; 7:3, s. 1369-1378
  • Tidskriftsartikel (refereegranskat)abstract
    • Amorphous carbon and amorphous, graphitic and fullerene-like carbon nitride thin filmswere deposited by reactive magnetron sputtering and optically characterized withspectroscopic ellipsometry. The films were exposed to human serum albumin and theadsorption was monitored in situ using dynamic ellipsometry. From the ellipsometric data theadsorbed amount of proteins was quantified in terms of surface mass density using de Feijter'smodel. The results indicated larger adsorption of proteins onto the amorphous films comparedto the films with a more ordered microstructure. Complementary studies with labeled HSAusing radioimmunoassay showed up to 6 times higher protein adsorption compared to theellipsometry measurement which partly might be explained by differences in surfaceroughness (from 0.3 to 13 nm) among the films. The elutability of adsorbed labeled HSAusing unlabeled HSA and sodium dodecyl sulphate was low compared to a silicon reference.In addition, the four types of films were incubated in blood plasma followed by antifibrinogen,anti-HMWK or anti-C3c revealing the materials response to complement andcontact activation. Three of the films indicated immunoactivity, whereas the amorphouscarbon showed less immunoactivity compared to a titanium reference. All films showedindications of a stronger ability to initiate the intrinsic pathway of coagulation, compared tothe reference. Finally, the surfaces bone bonding ability was investigated by examination oftheir ability to form calcium phosphate (CaP) crystals in a simulated body fluid, with a-CNxdepositing most CaP after 21 days of incubation.
10.
  • Broitman, Esteban, 1958-, et al. (författare)
  • Fullerene-like Carbon Nitride : A New Carbon-based Tribological Coating
  • 2008
  • Ingår i: Tribology of Diamond-Like Carbon Films : Fundamentals and Applications. - Springer. - 978-0-387-30264-5 - e-978-0-387-49891-1 - 0-387-3-0264-6 - 978-0-387-49891-1 ; s. 620-653
  • Bokkapitel (övrigt vetenskapligt)abstract
    • In 1994, researchers at Linköping University discovered the fullerene-like allotrope of carbon nitride (FL-CNx) by using reactive magnetron sputtering in a nitrogen-containing atmosphere at rather low ion energy assistance. FL-CNx is a predominantly sp2-hybridized material with nitrogen structurally incorporated either substitutionally in a graphite sheet or in a pyridine-like manner, which initiates bending by formation of pentagons and cross-linking, respectively. The assumed nitrogen-induced cross-linkage between the sheets contributes considerably to the strength of FL-CNx by preventing interplanar slip. This results in an extremely fracture tough, elastic, and compliant material, which deforms by reversible bond rotation and bond angle deflection rather than slip and bond breaking.
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