| 1. |
- Jin, P., et al.
(författare)
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Epitaxial growth of W-doped VO2/V2O3 multilayer on a-Al2O3(110) by reactive magnetron sputtering
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 375:1-2, s. 128-131
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Tidskriftsartikel (refereegranskat)abstract
- Multilayer epitaxy with a W-VO2 top layer over a bottom layer of which the crystal phase depends on the starting oxygen flow, was done on a-Al2O3(110) by reactively sputtering a V-W (1.6 at.% wt.) alloy target at linearly increasing oxygen flow without interrupting film growth. For the film deposited in the oxygen flow from 10 to 26 sccm, a W-VO2/W-V2O3 multilayer was formed on a-Al2O3(110) with the epitaxial relationship being (001)f?(110)s, (110)f?(001)s for W-V2O3, and (010)f?(110)s, (100)f?(001)s for W-VO2 where f and s denote the film and substrate, respectively. The formation of a triple domain structure was confirmed in the W-VO2 top layer due to the strong influence from the symmetry of the substrate. The multilayer shows phase transition behavior differing from the single layer film, which was presumably due to the effects of W-doping, compositional gradient, and strain.
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| 2. |
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| 3. |
- Olsson, M.K., et al.
(författare)
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Mechanisms for reactive DC magnetron sputtering of elements with different atomic masses : Large area coatings of Al oxide and W oxide
- 2000
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 371:1, s. 86-94
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Tidskriftsartikel (refereegranskat)abstract
- Stoichiometric Al and W oxide films are prepared with high stability from the metallic state of the cathodes using conventional reactive DC magnetron sputtering on an industrial prototype scale. While for the Al, increased target power is a trivial way to increase growth rates, W oxide sputtering of optically functional films with sufficiently amorphous structure is severely limited by the effect of gas rarefaction at high powers. Choosing an appropriate working gas pressure and a source-to-substrate distance, which facilitates the gas scattering allows the deposition of homogeneous stoichiometric tungsten oxide films in a stable condition with a relatively high discharge current. Optimization of the process parameters with respect to film properties and efficiency of the deposition process is discussed.
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| 4. |
- Hellgren, N, et al.
(författare)
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Influence of plasma parameters on the growth and properties of magnetron sputtered CNx thin films
- 2000
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Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 88:1, s. 524-532
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Tidskriftsartikel (refereegranskat)abstract
- Carbon nitride CNx thin films were grown by unbalanced dc magnetron sputtering from a graphite target in a pure N-2 discharge, and with the substrate temperature T-s kept between 100 and 550 degrees C. A solenoid coil positioned in the vicinity of the substrate was used to support the magnetic field of the magnetron, so that the plasma could be increased near the substrate. By varying the coil current and gas pressure, the energy distribution and fluxes of N-2(+) ions and C neutrals could be varied independently of each other over a wide range. An array of Langmuir probes in the substrate position was used to monitor the radial ion flux distribution over the 75-mm-diam substrate, while the flux and energy distribution of neutrals was estimated through Monte Carlo simulations. The structure, surface roughness, and mechanical response of the films are found to be strongly dependent on the substrate temperature, and the fluxes and energies of the deposited particles. By controlling the process parameters, the film structure can thus be selected to be amorphous, graphite-like or fullerene-like. When depositing at 3 mTorr N-2 pressure, with T-s> 200 degrees C, a transition from a disordered graphite-like to a hard and elastic fullerene-like structure occurred when the ion flux was increased above similar to 0.5-1.0 mA/cm(2). The nitrogen-to-carbon concentration ratio in the films ranged from similar to 0.1 to 0.65, depending on substrate temperature and gas pressure. The nitrogen film concentration did, however, not change when varying the nitrogen ion-to-carbon atom flux ratios from similar to 1 to 20. (C) 2000 American Institute of Physics. [S0021-8979(00)00413-8].
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| 5. |
- Jansik, B., et al.
(författare)
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Relativistic effects on linear and non-linear polarizabilities of the furan homologues
- 2003
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Ingår i: Journal of Molecular Structure. - : Elsevier BV. - 0166-1280. ; 633:03-feb, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- First principles calculations including relativistic effects are carried out for dipole moments, polarizabilities, first- and second-order hyperpolarizabilities for the series of furan homologues XC4H4, X = O, S, Se, Te, at three different levels of theory; time-dependent Dirac-Hartree-Fock (DHF), time-dependent Hartree-Fock with a Douglas-Kroll transformed one-component Hamiltonian, and time-dependent Hartree-Fock using effective-core potentials. By comparison with the corresponding non-relativistic results, the influence of relativistic effects on the properties as well as the accuracy of previously reported calculations on these molecules using effective-core potentials for selenium and tellurium can be addressed. The obtained results indicate that relativistic effects can be described with comparable accuracy at all three employed levels, and that non-scalar effects, which are explicitly treated only at the time-dependent DHF level, are of minor importance. Frequency dispersion and relativity are found to be additive at the single-determinant level. We find that relativistic effects cannot make up for the earlier identified mismatch between theory and experiment for the non-linear polarizabilities of the heavier homologues. A Bishop-Kirtman analysis of vibrational effects indicates that the same can be said about these.
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| 6. |
- Jansik, B., et al.
(författare)
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Relativistic effects on linear and non-linear polarizabilities of the furan homologues
- 2003
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Ingår i: Journal of Molecular Structure. - 0166-1280. ; 633:2-3, s. 237-246
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Tidskriftsartikel (refereegranskat)abstract
- First principles calculations including relativistic effects are carried out for dipole moments, polarizabilities, first- and second-order hyperpolarizabilities for the series of furan homologues XC4H 4, X = O, S, Se, Te, at three different levels of theory, time-dependent Dirac-Hartree-Fock (DHF), time-dependent Hartree-Fock with a Douglas-Kroll transformed one-component Hamiltonian, and time-dependent Hartree-Fock using effective-core potentials. By comparison with the corresponding non-relativistic results, the influence of relativistic effects on the properties as well as the accuracy of previously reported calculations on these molecules using effective-core potentials for selenium and tellurium can be addressed. The obtained results indicate that relativistic effects can be described with comparable accuracy at all three employed levels, and that non-scalar effects, which are explicitly treated only at the time-dependent DHF level, are of minor importance. Frequency dispersion and relativity are found to be additive at the single-determinant level. We find that relativistic effects cannot make up for the earlier identified mismatch between theory and experiment for the non-linear polarizabilities of the heavier homologues. A Bishop-Kirtman analysis of vibrational effects indicates that the same can be said about these. © 2003 Elsevier B.V. All rights reserved.
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| 7. |
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| 8. |
- Macak, K., et al.
(författare)
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Ionized sputter deposition using an extremely high plasma density pulsed magnetron discharge
- 2000
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Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 18:4 II, s. 1533-1537
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Tidskriftsartikel (refereegranskat)abstract
- A high power density pulsed plasma discharge for ionized sputter deposition is studied. The temporal evolution of the plasma ion composition in high power pulsed magnetron sputtering is investigated and shows that Ar ions dominated the beginning of the pulse. As time elapsed, metal ions are detected and finally dominated the ion composition.
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| 9. |
- Olsson, MK, et al.
(författare)
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High rate reactive de magnetron sputter deposition of Al2O3 films
- 1998
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Ingår i: JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS. - : AMER INST PHYSICS. - 0734-2101. ; 16:2, s. 639-643
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Aluminum oxide films were produced by reactive de magnetron sputtering of Al in Ar+O-2. The composition of the films was characterized by Rutherford backscattering measurements. Stoichiometric films possessed excellent optical properties with a refractive
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| 10. |
- Wang, C. K., et al.
(författare)
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Effects of pi centers and symmetry on two-photon absorption cross sections of organic chromophores
- 2001
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 114:22, s. 9813-9820
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Tidskriftsartikel (refereegranskat)abstract
- We have theoretically examined a series of organic molecules that exhibit large two-photon absorption cross sections in the visible region and that have been synthesized in different laboratories. One- and two-photon absorption cross sections of the four lowest excited states of each molecule have been calculated at the same theoretical level using ab initio response theory. It is found that the molecular length and the one-photon absorption intensity are quite strongly correlated factors, but that a corresponding correlation for the two-photon absorption is much weaker or is missing. In contrast, a most crucial role for large two-photon absorption is played by the pi center. For molecules with a given pi center a symmetrical structure with strong donor groups can result in a maximum two-photon absorption cross section. Our theoretical findings are consistent with some recent experimental observations. The chromophore based on dithienothiophene as pi center attached with symmetrical N,N-diphenylamine donors is found to have the largest two-photon cross section in the visible region among all known one-dimensional two-photon organic materials that have been reported in the literature.
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