| 1. |
- Buyanova, Irina, 1960-, et al.
(author)
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Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties of GaNxP1−x alloys : a proof for a general property of dilute nitrides
- 2004
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In: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 70:24, s. 245215-245219
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Journal article (peer-reviewed)abstract
- Direct experimental evidence for dramatic effects of hydrogen incorporation on the electronic structure and lattice properties of GaNxP1−x alloys is presented. By employing photoluminescence excitation spectroscopy, postgrowth hydrogenation is shown to reopen the band gap of the GaNP alloys and to efficiently reduce the N-induced coupling between the conduction band states. By Raman spectroscopy, these effects are shown to be accompanied by hydrogen-induced breaking of the Ga-P bond in the alloy, evident from disappearance of the corresponding vibrational mode. According to the performed Raman and x-ray diffraction measurements, the hydrogenation is also found to cause a strong expansion of the GaNP lattice, which changes the sign of strain from tensile in the as-grown GaNP epilayers to compressive in the posthydrogenated structures, due to the formation of complexes between N and H.
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| 2. |
- Eriksson, Fredrik, et al.
(author)
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14.5% near-normal incidence reflectance of Cr/Sc x-ray multilayer mirrors for the water window
- 2003
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 28:24, s. 2494-2496
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Journal article (peer-reviewed)abstract
- Cr/Sc multilayer mirrors, synthesized by ion-assisted magnetron sputter deposition, are proved to have a high near-normal reflectivity of R = 14.5% at a grazing angle of 87.5degrees measured at the wavelength A = 3.11 nm, which is an improvement of more than 31% compared with previously published results. Elastic recoil detection analyses show that the mirrors contained as much as 15 at. % of N and traces of C and O. Soft x-ray reflectivity simulations reveal interface widths of sigma = 0.34 nm and an exceptionally small layer thickness drift of similar to1.6 X 10(-5) nm/multilayer period throughout the stack. Simulations show that a reflectivity of R = 25.6% is attainable if impurities and layer thickness drift can be eliminated. The abrupt interfaces are achieved with ion assistance with a low ion energy of 24 eV and high ion-to-metal flux ratios of 7.1 and 23.1 during Cr and Se sputter deposition, respectively. In addition, a near-normal incidence reflectivity of 5.5% for the C VI emission line (lambda = 3.374 nm) from a laser plasma source was verified.
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| 3. |
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| 4. |
- Johansson, G. A., et al.
(author)
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Compact soft x-ray reflectometer based on a line-emitting laser-plasma source
- 2001
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In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 72:1, s. 58-62
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Journal article (peer-reviewed)abstract
- We describe a compact soft x-ray reflectometer for in-house characterization of water-window multilayer optics. The instrument is based on a line-emitting, liquid-jet, laser-plasma source in combination with angular scanning of the studied multilayer optics. With a proper choice of target liquid and thin-film filters, one or a few lines of well-defined wavelength dominate the spectrum and multilayer periods are measured with an accuracy of 0.003 nm using a multi-line calibration procedure. Absolute reflectivity may also be estimated with the instrument. The typical measurement time is currently 10 min. Although the principles of the reflectometer may be used in the entire soft x-ray and extreme ultraviolet range, the current instrument is primarily directed towards normal-incidence multilayer optics for water-window x-ray microscopy, and is thus demonstrated on W/B4C multilayers for this wavelength range.
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| 5. |
- Nordin, M., et al.
(author)
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Residual stress formation in multilayered TiN/TaNx coatings during reactive magnetron sputter deposition
- 2000
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In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 18:6, s. 2884-2889
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Journal article (peer-reviewed)abstract
- Multilayered physical vapor deposited TiN/TaNx coatings were deposited on cemented carbide substrates using a dual target magnetron sputtering system. The coatings were investigated with respect to the influence of nitrogen partial pressure during deposition on the residual stress developed in the coatings. Furthermore, the fracture strength of the material, i.e., the magnitude of the tensile stress that the coating can support without cracking, was evaluated. It was found that, by increasing the nitrogen partial pressure, it is possible to change the stress from compressive to tensile. The highest tensile stress was about 3.6 GPa. Despite this high stress, the coating displayed no cracking. This implies that it is possible to grow TiN/TaNx multilayered coatings with high tensile fracture strength using dual magnetron sputtering and a high deposition temperature (about 680 °C).
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| 6. |
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| 7. |
- Aquila, Andrew L., et al.
(author)
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Measurements of the optical constants of scandium in the 50-1300 eV range
- 2004
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In: SPIE 5538, Optical Constants of Materials for UV to X-Ray Wavelengths. - : SPIE - International Society for Optical Engineering. ; , s. 64-71
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Conference paper (peer-reviewed)abstract
- Scandium containing multilayers have been produced with very high reflectivity in the soft x-ray spectrum. Accurate optical constants are required in order to model the multilayer reflectivity. Since there are relatively few measurements of the optical constants of Scandium in the soft x-ray region we have performed measurements over the energy range of 50-1,300 eV. Thin films of Scandium were deposited by ion-assisted magnetron sputtering at Linkoping University and DC Magnetron sputtering at CXRO. Transmission measurements were performed at the Advanced Light Source beamline 6.3.2. The absorption coefficient was deduced from the measurements and the dispersive part of the index of refraction was obtained using the Kramers-Kronig relation. The measured optical constants are used to model the near-normal incidence reflectivity of Cr/Sc multilayers near the Sc L2,3 edge.
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| 8. |
- Bernard, M, et al.
(author)
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Raman spectra of TiN/AlN superlattices
- 2000
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In: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 380:1-2, s. 252-255
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Journal article (peer-reviewed)abstract
- TiN (4.5 nm)/AIN (3, 6, 22 nm) superlattices deposited by DC magnetron sputtering on MgO(001) at a temperature of 850 degreesC exhibit Raman signals. They indicate N and Ti vacancies (as in thick TiN) in TiN1-x layers (x = 3 +/- 2%). x is higher for the sample with 3-nm thick AIN layers, which is ascribed to N diffusion from AIN (standing close to the TiN interfaces) to TiN. In comparison to Raman peaks of thick ALN, there are split signals of wurzite ALN phase, and a signal from another phase, which might be defective rocksalt AIN standing close to the TiN interfaces. The Raman signals clearly show interactions between ALN and TiN layers. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 9. |
- Beshkova, Milena, et al.
(author)
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Low-pressure sublimation epitaxy of AlN films - growth and characterization
- 2004
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In: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 76, s. 143-146
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Journal article (peer-reviewed)abstract
- Epitaxial layers of aluminum nitride have been grown at temperatures 1900-2400degreesC on 10 x 10 mm(2) 4H-SiC substrate via sublimation recondensation in an RF heated graphite furnace. The source material was polycrystalline sintered AlN. A maximum growth rate of about 100 mum/h was achieved at 2400degreesC and seed to source distance of 1 mm. The surface morphology reflects the hexagonal symmetry of the seed suggesting an epitaxial growth. This was confirmed by X-ray diffraction (XRD). The spectra showed very strong and well-defined (0002) reflection position at around 36.04degrees in symmetric Theta-2Thetascans for all samples. Micro-Raman spectroscopy reveals that the films have a wurtzite structure. It is evidenced by the appearance of the A(1) (TO) (at 601 cm(-1)) and E-2((2)) (at 651 cm(-1)) lines in the spectra. Secondary-ion mass spectroscopy (SIMS) results showed a low concentration of carbon incorporation in the AlN films. A correlation between the growth conditions and properties of the AlN layers was established.
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| 10. |
- Birch, Jens, et al.
(author)
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Recent advances in ion-assisted growth of Cr/Sc multilayer X-ray mirrors for the water window
- 2002
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In: Vacuum. - 0042-207X .- 1879-2715. ; 68:3, s. 275-282
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Journal article (peer-reviewed)abstract
- Cr/Sc multilayer X-ray mirrors intended for normal incidence reflection in the water window wavelength range, lambda=[2.4-4.4 nm], have been grown by ion-assisted sputter deposition and characterized using soft and hard X-ray reflectivity. By extracting low-energy ions, with energies, E-ion, ranging from 9 to 113 eV and with ion-to-metal flux ratios, Phi, between 0.76 and 23.1, from the sputtering plasma to the growing film, the nano-structure of the multilayer interfaces could be modified. A significantly increased soft X-ray reflectivity, using lambda = 3.374 nm, for Cr/Sc multilayers with layer thicknesses in the range 0.4-2.8 nm, was obtained when high ion-to-metal flux ratios, Phi(Cr) = 7.1 and Phi(Sc) = 23.1, and low energy ions, E-ion = 9eV, were used. An experimental reflectivity of 5.5% was obtained at 76degrees for a multilayer with 400 bi-layers. Simulations of the reflectivity data showed that the interface widths are < 0.425 nm. It could be concluded that roughness of low spatial frequency is reduced at lower ion energies than the high spatial frequency which was eliminated at the expense of intermixing at the interfaces at higher ion energies. The predicted performance of normal incidence multilayer mirrors grown at optimum conditions and designed for lambda = 3.374 and 3.115 nm indicates possible reflectivities of 6.5% and 14%, respectively.
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