| 41. |
- Qviller, A. J., et al.
(författare)
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Thermal stability of photovoltaic a-Si:H determined by neutron reflectometry
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:23, s. 231909-
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Tidskriftsartikel (refereegranskat)abstract
- Neutron and X-ray reflectometry were used to determine the layer structure and hydrogen content of thin films of amorphous silicon (a-Si:H) deposited onto crystalline silicon (Si) wafers for surface passivation in solar cells. The combination of these two reflectometry techniques is well suited for non-destructive probing of the structure of a-Si:H due to being able to probe buried interfaces and having sub-nanometer resolution. Neutron reflectometry is also unique in its ability to allow determination of density gradients of light elements such as hydrogen (H). The neutron scattering contrast between Si and H is strong, making it possible to determine the H concentration in the deposited a-Si:H. In order to correlate the surface passivation properties supplied by the a-Si:H thin films, as quantified by obtainable effective minority carrier lifetime, photoconductance measurements were also performed. It is shown that the minority carrier lifetime falls sharply when H has been desorbed from a-Si:H by annealing. (C) 2014 AIP Publishing LLC.
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| 42. |
- Rantzer, Annika, 1971-, et al.
(författare)
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Optical properties of intrinsic and doped a-Si:H films grown by d.c. magnetron sputter deposition
- 2001
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Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 394:1-2, s. 255-262
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of intrinsic, B- and P-doped a-Si:H were grown by d.c. magnetron sputter deposition. The doping was accomplished by doped targets and co-sputtering Si and B4C. Spectroscopic ellipsometry was used for optical characterization and multiple sample analysis was applied to extract the dielectric functions of intrinsic films with 8–10 at.% hydrogen content, boron doped films with 2.2 at.% hydrogen and phosphorous-doped films with hydrogen contents of 10–15 at.%. One of the phosphorous-doped films was micro-crystalline. Hydrogen content was determined by nuclear reaction analysis. From the obtained optical properties the absorption and the optical gap were studied addressing p–i–n diode applications. The optical gaps for intrinsic a-Si:H material were 1.88±0.03 eV as determined by Tauc analysis and 1.45±0.06 eV by applying Cody analysis.
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| 43. |
- Rantzer, Annika, et al.
(författare)
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Sputter-deposited a-Si:H for p-i-n photodiodes
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- DC magnetron sputter deposition is explored as an alternative for fabricating vertically integrated sensor systems in the form of p-i-n diodes of hydrogenated amorphous silican deposited on CMOS integrated circuit substrates in a post-processing step. We focus here on dopant oncorporation and surface morphological evolution during synthesis of the p-i-n diode sensor structures. The Doping was accomplished using doped targets in a mixed H2/Ar environment. Incorporated P concetrations range from 2.62 to 4.8 x 1019 cm-3 with corresponding conductivities, σ, up to 1.4 x10-5 ohm-1cm-1. B contentrations are between 2.79 and 6.7 X 1020 cm-3 with σ = 4 x 10-5 to 4 x 10-2 ohm-1cm-1. The results of the dopant incorporation are in agreement with reported molecular dynamics simulations. The best intrinsic films have a light to dark conductivity ratio of 102 for white light at an intensity of 10 W/m2. The dark conductivity is a 8 x 10-9 ohm-1cm-1. We conclude that dc magnetron sputter deposition is a good candidate for future device fabrication.
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| 44. |
- Remhof, A., et al.
(författare)
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Hydrogen Functionalized Materials
- 2008
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Ingår i: Hydrogen as a Future Energy Carrier. - Weinheim : Verlag GmbH & Co. KGaA. - 9783527308170
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 45. |
- Rodrigues, Debora C. M., et al.
(författare)
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Magnetic anisotropy in permalloy : hidden quantum mechanical features
- 2018
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Ingår i: Physical Review B. - 2469-9950 .- 2469-9969. ; 97:22
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Tidskriftsartikel (refereegranskat)abstract
- By means of relativistic, first principles calculations, we investigate the microscopic origin of the vanishingly low magnetic anisotropy of Permalloy, here proposed to be intrinsically related to the local symmetries of the alloy. It is shown that the local magnetic anisotropy of individual atoms in Permalloy can be several orders of magnitude larger than that of the bulk sample and 5–10 times larger than that of elemental Fe or Ni. We furthermore show that locally there are several easy axis directions that are favored, depending on local composition. The results are discussed in the context of perturbation theory, applying the relation between magnetic anisotropy and orbital moment. Permalloy keeps its pronounced soft ferromagnetic nature due to the exchange energy to be larger than the magnetocrystalline anisotropy. Our results shine light on the magnetic anisotropy of permalloy and of magnetic materials in general, and in addition enhance the understanding of pump-probe measurements and ultrafast magnetization dynamics.
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| 46. |
- Stopfel, Henry, et al.
(författare)
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Multiple energy scales in mesospin systems : The vertex-frustrated Saint George lattice
- 2021
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Ingår i: Physical Review Materials. - : American Physical Society. - 2475-9953. ; 5:11
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Tidskriftsartikel (refereegranskat)abstract
- The interplay between topology and energy hierarchy plays a vital role in the collective magnetic order in artificial ferroic systems. Here we investigate, experimentally, the effect of having one or two activation energies of interacting Ising-like magnetic islands—mesospins—in thermalized, vertex-frustrated lattices. The thermally arrested magnetic states of the elements were determined using synchrotron-based magnetic microscopy after cooling the samples from temperatures above the Curie temperature of the material. Statistical analysis of the correlations between mesospins across several length scales reveals changes in the magnetic order, reflecting the amount of ground state plaquettes realized for a vertex-frustrated lattice. We show that the latter depends on the presence, or not, of different activation energies.
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| 47. |
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| 48. |
- Thorarinsdottir, K. A., et al.
(författare)
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Finding order in disorder : Magnetic coupling distributions and competing anisotropies in an amorphous metal alloy
- 2022
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Ingår i: APL Materials. - : American Institute of Physics (AIP). - 2166-532X. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous metals have unusual magnetic properties that arise due to the disordered atomic arrangement. We show that Co-x(Al70Zr30)(100-x) (65 < x < 92 at.%) amorphous alloys have a distribution in the local magnetic coupling and ordering temperature, which can be explained by nanoscale composition variations. We use competing anisotropies induced by the substrate and an applied field during growth to probe the Co concentration distribution. Only regions with high enough Co concentration develop a magnetic anisotropy along the magnetic field during growth, whereas regions of low Co concentration have an anisotropy dictated by the substrate. A Gaussian distribution in the Co concentration of width 5.1 at.% is obtained from the variation in anisotropy. The results demonstrate the importance of composition variations for emergent magnetic properties and have far reaching implications for the properties of disordered materials in general.
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| 49. |
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| 50. |
- Van Kampen, M., et al.
(författare)
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On the realization of artificial XY spin chains
- 2005
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Ingår i: Journal of Physics. - 0953-8984 .- 1361-648X. ; 17:2, s. L27-L33
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Tidskriftsartikel (refereegranskat)abstract
- Spin chains are the most elementary entities in the study of magnetic ordering behavior. The authors describe a route toward the realization of artificial XY spin chains. Using thin-film deposition and e-beam lithog., 300 and 550 nm diam. pillars consisting of alternating disks of permalloy and Al2O3 were made. Shape anisotropy forces the magnetization in plane, creating a chain of two-dimensional magnetic moments →i. The disks couple to each other by their dipolar stray fields, resulting in an interaction Jij→i·→j, with Jij the coupling between disks i and j. This form closely resembles a chain of xy spins, coupled by effective interactions Jij. The authors present a magnetic characterization of the pillars, and compare the results with model calcns. Also, spin dynamics and ordering phenomena are addressed.
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