| 1. |
- Qadir Israr, Muhammed, et al.
(författare)
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Potentiometric cholesterol biosensor based on ZnO nanorods chemically grown on Ag wire
- 2010
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 519:3, s. 1106-1109
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Konferensbidrag (refereegranskat)abstract
- An electrochemical biosensor based on ZnO nanorods for potentiometric cholesterol determination is proposed. Hexagon-shaped ZnO nanorods were directly grown on a silver wire having a diameter of 250 mu m using low temperature aqueous chemical approach that produced ZnO nanorods with a diameter of 125250 nm and a length of similar to 1 mu m. Cholesterol oxidase (ChOx) was immobilized by a physical adsorption method onto ZnO nanorods. The electrochemical response of the ChOx/ZnO/Ag biosensor against a standard reference electrode (Ag/AgCl) was investigated as a logarithmic function of the cholesterol concentration (1 x 10(-6)M to 1 x 10(-2)M) showing good linearity with a sensitivity of 35.2 mV per decade and the stable output signal was attained at around 10 s. (C) 2010 Elsevier BM. All rights reserved.
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| 2. |
- Chirita, V, et al.
(författare)
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Strain relaxation and thermal stability of the 3C-SiC(001)/Si(001) interface : A molecular dynamics study
- 1997
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Ingår i: Thin Solid Films. - 0040-6090. ; 294:1-2, s. 47-49
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics (MD) and high-resolution electron microscopy (HREM) imaging are used to investigate the mechanism of strain relaxation of a model 3C-SiC(001)/Si(001) interface. It is found that the essential atomic mechanism governing this process is the formation of undulations in planes parallel and perpendicular to the interface. The net effect is the generation of misfit-accommodating dislocations, of the [removed] type, which allow for structure relaxation at 2, 700 and 1000 K. MD configurations are then used for HREM image simulations. Comparisons with actual HREM images of the interface support the model interface and relaxation mechanisms proposed herein.
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| 3. |
- Krupin, OW, et al.
(författare)
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Ferrimagnetic 4f spin order in O/Gd surface monoxide
- 2003
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Ingår i: Thin Solid Films. - 0040-6090. ; 428:1-2, s. 98-101
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Tidskriftsartikel (refereegranskat)abstract
- The remanent 4f spin structure of the epitaxial surface monoxide O(1 X 1)/Gd(0001) has been investigated using magnetic dichroism in core-level photoemission (MDPE). Here we report the observation of a substantial dichroic signal of the chemically shifted Gd-4f PE line. It demonstrates the presence of a non-vanishing net magnetization of the surface monoxide layer at cryogenic temperatures. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
- Oberg, K., et al.
(författare)
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Comparison of monolayer films of stearic acid and methyl stearate on an Al2O3 surface
- 2001
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Ingår i: Thin Solid Films. - : Elsevier. - 0040-6090. ; 397:1-2, s. 102-8
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Tidskriftsartikel (refereegranskat)abstract
- Both stearic acid and methyl stearate chemisorbs onto an oxide surface of aluminum with an asymmetric coordination of the carboxylate group as concluded from infrared (IR) spectroscopy data. Similarities in the IR spectra of the films from the two compounds suggest that the ester is bonded in the same way as the acid, and that the ester therefore undergoes hydrolysis during the surface reaction. X-Ray photoelectron spectroscopy (XPS) and IR data are interpreted in terms of self-assembled monolayer formation and a more dense film from the carboxylic acid in comparison with that from the ester. (C) 2001 Elsevier Science B.V. All rights reserved.
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| 5. |
- Selinder, T.I., et al.
(författare)
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Structural characterization of yttria (Y2O3) inclusions in YBa2Cu3O7−x films : Growth model and effect on critical current density
- 1993
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Ingår i: Thin Solid Films. - 0040-6090. ; 229:2, s. 237-248
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Tidskriftsartikel (refereegranskat)abstract
- A higher critical current and enhanced pinning was obtained in c-axis-oriented YBa2Cu3O7−x (YBCO)films having a higher density of semicoherent yttria (Y2O3) inclusions. The films were grown by sputtering and the inclusion density depends on the fraction of N2O in the sputtering gas. The inclusions were studied by transmission electron microscopy, both in planar sections and in cross-sections. They are embedded in the YBCO matrix without disturbing its structure appreciably, and the inclusion density is up to about 1017 cm−3, comprising about 4% of the film volume. From the appearance of moiré fringes and from high resolution transmission electron micrographs, it is concluded that the inclusions are highly oriented and have coherent or semicoherent interfaces towards matrix. A model for formation of the yttria inclusions during film growth is presented, which includes nucleation of epitaxial coherent yttria islands, layer-by-layer growth and finally overgrowth by advancing steps of the YBCO film. The enhanced pinning and transport critical current densities, relation to film microstructure and the possible flux-pinning mechanisms by these yttria inclusions are discussed.
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| 6. |
- Sjöström, H., et al.
(författare)
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Microstructure of amorphous C:H and metal-containing C:H films deposited on steel substrates
- 1993
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Ingår i: Thin Solid Films. - 0040-6090. ; 232:2, s. 169-179
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Tidskriftsartikel (refereegranskat)abstract
- Cross-sectional transmission electron microscopy (XTEM), including high-resolution microscopy (HREM), was employed to characterize the interface between different amorphous hydrogenated carbon (a-C:H) films and steel substrates. Additional analyses using Auger electron spectroscopy (AES) and X-ray diffraction (XRD) were also performed. Films were deposited both by high-energy (50 keV) nitrogen ion-beam decomposition of large hydrocarbon molecules and by magnetron plasma decomposition of C2H2 in mixed Ar-C2H2 discharges. The latter method was also used to deposit Mo- or W-containing a-C:H films (Me-C:H films) onto steel substrates with interlayers of the pure metals between the substrate and Me-C:H film. The films were found to be truly amorphous except for the cases of the metal-containing films, where 1–2 nm crystalline clusters were present in an a-C:H matrix. In the case of Mo the clusters were identified from HREM micrographs to have a bcc-like structure, characteristic of metallic Mo. The metal interlayers had a columnar microstructure with column widths of ∼ 30 nm. The interfaces between the Mo and W interlayers and the a-C:H films were found to extend over 20–40 nm with a gradual crystalline-to-amorphous transition. In most of the a-C:H film-substrate interface regions a thin layer ( < 10 nm) was observed which was predominantly amorphous but contained a small fraction of crystalline grains. AES showed an increase of both O and N close to the interface. However, for the cases with Mo and W interlayers, the substrate surface contaminants were less localized, and on some parts of the substrate surface the lattice fringes of the substrate and metal interlayer phase were continuous across a sharp interface.
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| 7. |
- Sjöström, H, et al.
(författare)
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Reactive magnetron sputter deposition of CNx films on Si(001) substrates : film growth, microstructure and mechanical properties
- 1994
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090. ; 246:1-2, s. 103-109
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Tidskriftsartikel (refereegranskat)abstract
- There is currently considerable interest in producing new materials with extreme combinations of mechanical properties such as high hardnesses and moduli. One example of such a material is crystalline C3N4, which has been predicted to have a bulk modulus higher than that of diamond. In this paper we report on experiments carried out to synthesize CNx thin films. The films were grown in an unbalanced magnetron-sputtering system by reactive sputtering of C in N2 discharges. Si(001) substrates with the native oxide removed by thermal desorption and then kept at temperatures ranging from 150 to 600°C and substrate bias voltages Vs between 7.5 and -200 V were used. The films were analysed using X-ray diffraction, transmission electron microscopy (TEM). Auger electron spectroscopy, Rutherford backscattering and nano-indentation tests. Typically the films were grown at rates of 5 nm s-1 to total thicknesses of 300 nm. Owing to an extensive re-sputtering, only low negative bias voltages (-80
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| 8. |
- Alfredsson, Y, et al.
(författare)
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Phase and molecular orientation in metal-free phthalocyanine films on conducting glass: Characterization of two deposition methods
- 2005
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090. ; 493:1-2, s. 13-19
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Tidskriftsartikel (refereegranskat)abstract
- in this study, metal-free phthalocyanine has been deposited on a conducting glass surface by two methods: by spreading the molecular powder directly on the substrate in air and by vapor sublimation under ultra-high vacuum conditions (evaporation). The films have been characterized by means of core level X-ray Photoemission Spectroscopy, X-ray Absorption Spectroscopy (XAS) and Ultra Violet and Visible absorption spectroscopy (UV-Vis). Our results show that the two deposition methods produce molecular overlayers in different polymorphic phases; the UV-Vis measurements indicate that the film obtained by powder deposition is of x-phase type whereas sublimation leads to an a-polymorph structure. The XAS results show that in the powder deposited film the molecules are mainly oriented parallel to the surface. This is opposite to the case of the vapor deposited film, where the molecules mainly are oriented orthogonal to the surface.
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| 9. |
- Edström, Helen, et al.
(författare)
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Alloying and Oxidation of PdAu Thin Films
- 2024
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Ingår i: Thin Solid Films. - 0040-6090. ; 790
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Tidskriftsartikel (refereegranskat)abstract
- The relation between catalytic activity and the presence of oxides on the catalyst’s surface has proven very complex, especially in the case of methane oxidation over Pd. While the metallic Pd surface and a thin, but at least two atomic layers thick, oxide film has been found catalytically active, a single-layer surface oxide or a too thick oxide film are both low-active. Unfortunately, under reaction conditions, the oxide tends to grow thick and deactivate. The reason for this deactivation is believed to be exposure of the PdO(100) surface, which does not have any suitable active sites for the methane adsorption and activation, in contrast to PdO(101), which is exposed for thin films. In an attempt to limit the thickness of the oxide film, and hence stabilise the active PdO orientation, we have investigated the oxidation of thin PdAu films. The effects of different mixtures (25%, 50%, and 75% Au, respectively) and treatments on the oxidation and orientation of the alloy and oxide films were investigated. As intended, PdAu turned out to be significantly more difficult to oxidise compared to pure Pd. This effect was even stronger than expected. Depending on the amount of Au present in the alloy, the orientation of the oxide is affected. At lower Au concentration, the desired (101) oxide orientation is favoured, while higher Au concentration favours the low-active (100) oxide orientation. Thus, PdAu might be a good candidate for methane oxidation if the Au concentration is low, probably below 25%. The larger lattice constant of Au compared to Pd might also affect the oxide orientation, so another choice of alloying material, e.g. PdPt, may also work to stabilise PdO(101).
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| 10. |
- Koksharov, Yu.A., et al.
(författare)
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Magnetostatic interactions in planar ring-like nanoparticle structures
- 2006
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Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090. ; 515, s. 731-734
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Tidskriftsartikel (refereegranskat)abstract
- Numerical calculations of equilibrium state energies and local magnetic fields in planar ring-like nanoparticle structures were performed. The dipole–dipole, Zeeman and magnetic anisotropy interactions were included into the model. The result of their competition depends on the value of the external magnetic field, magnetic parameters of an individual nanoparticle, size and shape of the structures. Flux-closed vortexes, single domain, two- domain ‘‘onion’’-like, ‘‘hedgehog’’-like and more complex spin structures can be realized. The critical field, providing a sharp transition from the flux-closed vortex to the ‘‘onion’’-like state, can be regulated by a variation of the particle magnetization and anisotropy constant, their easy directions, and particle space arrangement.
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