| 61. |
- Junesand, Carl, et al.
(författare)
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Heteroepitaxial Indium Phosphide on Silicon
- 2010
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Ingår i: SILICON PHOTONICS AND PHOTONIC INTEGRATED CIRCUITS II. - : SPIE. - 9780819481924 ; , s. Q-1-Q-9
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- There is an intense interest on integration of III-V materials on silicon and silicon-on-insulator for realisation of optical interconnects, optical networking, imaging and disposable photonics for medical applications. Advances in photonic materials, structures and technologies are the main ingredients of this pursuit. We investigate nano epitaxial lateral overgrowth (NELOG) of InP material from the nano openings on a seed layer on the silicon wafer, by hydride vapour phase epitaxy (HVPE). The grown layers were analysed by cathodoluminescence (CL) in situ a scanning electron microscope, time-resolved photoluminescence (TR-PL), and atomic force microscope (AFM). The quality of the layers depends on the growth parameters such as the V/III ratio, growth temperature, and layer thickness. CL measurements reveal that the dislocation density can be as low as 2 - 3.10(7) cm(-2) for a layer thickness of similar to 6 mu m. For comparison, the seed layer had a dislocation density of similar to 1.10(9) cm(-2). Since the dislocation density estimated on theoretical grounds from TRPL measurements is of the same order of magnitude both for NELOG InP on Si and on InP substrate, the dislocation generation appears to be process related or coalescence related. Pertinent issues for improving the quality of the grown InP on silicon are avoiding damage in the openings due to plasma etching, pattern design to facilitate coalescence with minimum defects and choice of mask material compatible with InP to reduce thermal mismatch.
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| 62. |
- Junesand, Carl, et al.
(författare)
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Study of planar defect filtering in InP grown on Si by epitaxial lateral overgrowth
- 2013
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Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 3:11, s. 1960-1973
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Tidskriftsartikel (refereegranskat)abstract
- InP thin films have been grown on InP/Si substrate by epitaxial lateral overgrowth (ELOG). The nature, origin and filtering of extended defects in ELOG layers grown from single and double openings in SiO2 mask have been investigated. Whereas ELOG layers grown from double openings occasionally exhibit threading dislocations (TDs) at certain points of coalescence, TDs are completely absent in ELOG from single openings. Furthermore, stacking faults (SFs) observed in ELOG layers grown from both opening types originate not from coalescence, but possibly from formation during early stages of ELOG or simply propagate from the seed layer through the mask openings. A model describing their propagation is devised and applied to the existent conditions, showing that SFs can effectively be filtered under certain conditions. ELOG layers grown from identical patterns on InP substrate contained no defects, indicating that the defect-forming mechanism is in any case not inherent to ELOG itself.
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| 63. |
- Karlsson, Linda H., et al.
(författare)
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Atomically resolved microscopy of ion implantation induced dislocation loops in 4H-SiC
- 2016
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Ingår i: Materials letters (General ed.). - : Elsevier. - 0167-577X .- 1873-4979. ; 181, s. 325-327
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Tidskriftsartikel (refereegranskat)abstract
- During high temperature electrical activation of ion-implanted dopant species in SiC, extrinsic dislocation loops are formed on the basal planes of the SiC lattice. Investigations have suggested Si-based loops are caused in accordance with the well-known +1 model. Herein we apply aberration corrected STEM to resolve the atomic structure of these loops. It is shown that the dislocation loops formed during annealing of Al-implanted SiC consist of an extra inserted Si-C bilayer of the (0001) polar sense, which upon insertion into the lattice causes a local extrinsic stacking fault. The +1 model thus needs to be expanded for binary systems. (C) 2016 Elsevier B.V. All rights reserved.
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| 64. |
- Kostov Gueorguiev, Gueorgui, et al.
(författare)
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Intercalation of P atoms in Fullerene-like CPx
- 2011
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Ingår i: CHEMICAL PHYSICS LETTERS. - : Elsevier Science B.V., Amsterdam.. - 0009-2614 .- 1873-4448. ; 501:4-6, s. 400-403
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Tidskriftsartikel (refereegranskat)abstract
- The energy cost for P atom intercalation and corresponding structural implications during formation of Fullerene-like Phosphorus carbide (FL-CPx) were evaluated within the framework of Density Functional Theory. Single P atom interstitial defects in FL-CPx are energetically feasible and exhibit energy cost of 0.93-1.21 eV, which is comparable to the energy cost for experimentally confirmed tetragon defects and dangling bonds in CPx. A single P atom intercalation event in FL-CPx can increase the inter-sheet distance from 3.39-3.62 angstrom to 5.81-7.04 angstrom. These theoretical results are corroborated by Selected Area Electron Diffraction characterization of FL-CPx samples.
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| 65. |
- Kubart, Tomas, et al.
(författare)
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Experiments and Modelling of Dual Reactive Magnetron Sputtering Using Two Reactive Gases
- 2008
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 26:4, s. 565-570
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Tidskriftsartikel (refereegranskat)abstract
- Reactive sputtering from two elemental targets, aluminium and zirconium, with the addition of two reactive gases, oxygen and nitrogen, is studied experimentally as well as theoretically. The complex behaviour of this process is observed and explained. It is shown that the addition of oxygen to a constant supply of nitrogen, significantly changes the relative content of aluminium with respect to zirconium in the film. Moreover, it is concluded that there is substantially more oxygen than nitrogen in the films even when the oxygen supply is significantly lower than the nitrogen supply. It is further shown that the addition of a certain minimum constant flow of nitrogen reduces, and eventually eliminates, the hysteresis with respect to the oxygen supply. It is concluded that the presented theoretical model for the involved reactions and mass balance during reactive sputtering of two targets in two reactive gases is in qualitative agreement with the experimental results and can be used to find optimum processing conditions for deposition of films of a desired composition.
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| 66. |
- Lagerqvist, Ulrika, et al.
(författare)
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Morphology effects on exchange anisotropy in Co-CoO nanocomposite films
- 2015
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 576, s. 11-18
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Tidskriftsartikel (refereegranskat)abstract
- Co-CoO composite films were prepared by solution chemical technique using amine-modified nitrates and acetates in methanol. We study how particle size and porosity can be tuned through the synthesis parameters and how this influences the magnetic properties. Phase content and microstructure were characterised with grazing incidence X-ray diffraction and electron microscopy, and the magnetic properties were studied by magnetometry and magnetic force microscopy. Composite films were obtained by heating spin-coated films in Ar followed by oxidation in air at room temperature, and the porosity and particle size of the films were controlled by gas flow and heating rate. The synthesis yielded dense films with a random distribution of metal and oxide nanoparticles, and layered films with porosity and sintered primary particles. Exchange anisotropy, revealed as a shift towards negative fields of the magnetic hysteresis curve, was found in all films. The films with a random distribution of metal and oxide nanoparticles displayed a significantly larger coercivity and exchange anisotropy field compared to the films with a layered structure, whereas the layered films displayed a larger nominal saturation magnetisation. The magnitude of the coercivity decreased with increasing Co grain size, whereas increased porosity caused an increased tilt of the magnetic hysteresis curve. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license
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| 67. |
- Landälv, Ludvig, 1982-, et al.
(författare)
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Phase composition and transformations in magnetron-sputtered (Al,V)2O3 coatings
- 2019
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 688
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Tidskriftsartikel (refereegranskat)abstract
- Coatings of (Al1-xVx)2O3, with x ranging from 0 to 1, were deposited by pulsed DC reactive sputter deposition on Si(100) at a temperature of 550 °C. XRD showed three different crystal structures depending on V-metal fraction in the coating: α-V2O3 rhombohedral structure for 100 at.% V, a defect spinel structure for the intermediate region, 63–42 at.% V. At lower V-content, 18 and 7 at.%, a gamma-alumina-like solid solution was observed, shifted to larger d-spacing compared to pure γ-Al2O3. The microstructure changes from large columnar faceted grains for α-V2O3 to smaller equiaxed grains when lowering the vanadium content towards pure γ-Al2O3. Annealing in air resulted in formation of V2O5 crystals on the surface of the coating after annealing to 500 °C for 42 at.% V and 700 °C for 18 at.% V metal fraction respectively. The highest thermal stability was shown for pure γ-Al2O3-coating, which transformed to α-Al2O3 after annealing to 1100 °C. Highest hardness was observed for the Al-rich oxides, ~24 GPa. The latter decreased with increasing V-content, larger than 7 at.% V metal fraction. The measured hardness after annealing in air decreased in conjunction with the onset of further oxidation of the coatings.
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| 68. |
- Lauridsen, Jonas, et al.
(författare)
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Effects of A-elements (A=Si, Ge or Sn) on the structure and electrical contact properties of Ti-A-C-Ag nanocomposites
- 2012
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 520:16, s. 5128-5136
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Tidskriftsartikel (refereegranskat)abstract
- Ti-A-C-Ag (A is Si, Ge or Sn) nanocomposite coatings have been deposited by dc magnetron sputtering in an ultra high vacuum chamber. Electron microscopy, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and x-ray diffraction show that all coatings contain nanocrystalline TiC and Ag grains in a matrix of mainly amorphous C. A C/Ti ratio above unity yields a homogenous distribution of Ag with a reduced grain size. From a chemical point of view. the addition of Ge and Sn to the Ti-C-Ag system should increase the conductivity of the coatings since the formation of more metallic phases than Si. We demonstrate that Si can be replaced with Ge and Sn and still yield a homogeneous distribution of Ag. The incorporation of Ge and Sn to the Ti-C-Ag system results in elemental precipitation and intermetallic phases, respectively. This gives improved electrical properties compared to Ti-Si-C-Ag coatings, and a contact resistance at loads of similar to 1 N against an Au probe (radius of 0.7 mm) that is comparable to that of Ag.
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| 69. |
- Lauridsen, Jonas, et al.
(författare)
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High-rate deposition of amorphous and nanocomposite Ti-Si-C multifunctional coatings
- 2010
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Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 205:2, s. 299-305
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous (a) and nanocomposite Ti-Si-C coatings were deposited at rates up to 16 mu m/h by direct current magnetron sputtering from a Ti3SiC2 compound target, using an industrial pilot-plant system, onto high-speed steel. Si, and SiO2 substrates as well as NI-plated Cu cylinders, kept at a temperature of 200 or 270 degrees C. Electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses showed that TiC/a-C/a-SiC nanocomposites were formed consisting of textured TIC nanocrystallites (nc) embedded in a matrix of a-C and a-SiC. Elastic recoil detection analysis showed that coatings deposited at a target-to-substrate distance of 2 cm and an Ar pressure of 10 mTorr have a composition close to that of the Ti3SiC2 compound target, as explained by ballistic transport of the species Increased target-to-substrate distance from 2 cm to 8 cm resulted in a higher carbon-to-titanium ratio in the coatings than for the Ti3SiC2 compound target, due to different gas-phase scattering properties between the sputtered species The coating microstructure could be modified from nanocrystalline to predominantly amorphous by changing the pressure and target-to-substrate conditions to 4 mTorr and 2 cm, respectively. A decreased pressure from 10 mTorr to 4 or 2 mTorr at a target-to-substrate distance of 2 cm decreased the deposition rate up to a factor of similar to 7 as explained by resputtering and an increase in the plasma sheath thickness. The coatings exhibited electrical resistivity in the range 160-800 mu Omega cm, contact resistance down to 08 m Omega at a contact force of 40 N, and nanoindentation hardness in the range of 6-38 GPa.
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| 70. |
- Lauridsen, Jonas, et al.
(författare)
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Microstructure evolution of Ti-Si-C-Ag nanocomposite coatings deposited by DC magnetron sputtering
- 2010
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Ingår i: Acta Materialia. - : Elsevier Ltd.. - 1359-6454 .- 1873-2453. ; 58:20, s. 6592-6599
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite coatings consisting of Ag and TiCx (x < 1) crystallites in a matrix of amorphous SiC were deposited by high-rate magnetron sputtering from Ti-Si-C-Ag compound targets. Different target compositions were used to achieve coatings with a Si content of similar to 13 at.%, while varying the C/Ti ratio and Ag content. Electron microscopy, helium ion microscopy, X-ray photoelectron spectroscopy and X-ray diffraction were employed to trace Ag segregation during deposition and possible decomposition of amorphous SiC. Eutectic interaction between Ag and Si is observed, and the Ag forms threading grains which coarsen with increased coating thickness. The coatings can be tailored for conductivity horizontally or vertically by controlling the shape and distribution of the Ag precipitates. Coatings were fabricated with hardness in the range 10-18 GPa and resistivity in the range 77-142 mu Omega cm.
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