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- Coutinho, E., et al.
(författare)
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Ultrastructural characterization of tooth-biomaterial interfaces prepared with broad and focused ion beams
- 2009
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Ingår i: Dental Materials. - : Elsevier BV. - 0109-5641 .- 1879-0097. ; 25:11, s. 1325-1337
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Tidskriftsartikel (refereegranskat)abstract
- Current available techniques for transmission electron microscopy (TEM) of tooth biomaterial interfaces are mostly ineffective for brittle phases and impair integrated chemical and morphological characterization. Objectives. The aims of this study were (1) to determine the applicability of new focused ion beam (FIB) and broad ion beam (BIB) techniques for TEM preparation of tooth-biomaterial interfaces; (2) to characterize the interfacial interaction with enamel and dentin of a conventional glass-ionomer (Chem. l Superior, DeTrey Dentsply, Germany), a 2-step self-etch (Clear. l SE, Kuraray, Japan) and a 3-step etch-and-rinse (OptiBond FL, Kerr, USA) adhesives; and (3) to characterize clinically relevant interfaces obtained from actual Class-I cavities. Methods. After bonding to freshly extracted human third molars, non-demineralized and non-stained sections were obtained using the FIB/BIB techniques and examined under TEM. Results. The main structures generally disclosed in conventional ultramicrotomy samples were recognized in FIB/BIB-based ones. There were not any major differences between FIB and BIB concerning the resulting ultrastructural morphology. FIB/BIB-sections enabled to clearly resolve sub-micron hydroxyapatite crystals on top of hard tissues and the interface between matrix and filler in all materials, even at nano-scale. Some investigated interfaces disclosed areas with a distinct "fog" or "melted look", which is probably an artifact due to surface damage caused by the high-energy beam. Interfaces with enamel clearly disclosed the distinct "keyhole" shape of enamel rods sectioned at 90 degrees, delimited by a thin electron-lucent layer of inter-rod enamel. At regions where enamel crystals ran parallel with the interface, we observed a lack of interaction and some de-bonding along with interfacial void formation. Significance. The FIB/BIB methods are viable and reliable alternatives to conventional ultramicrotomy for preparation of thin sections of brittle and thus difficult to cut biomaterial-hard tissue interfaces. They disclose additional ultrastructural information about both substrates and are more suitable for advanced analytic procedures.
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| 2. |
- Edoff, Marika, 1965-, et al.
(författare)
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High Voc in (Cu,Ag)(In,Ga)Se2 Solar Cells
- 2017
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 7:6, s. 1789-1794
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Tidskriftsartikel (refereegranskat)abstract
- In this contribution, we show that silver substitution for copper in Cu(In,Ga)Se-2 (CIGS) to form (Ag,Cu)(In, Ga)Se-2 (ACIGS) leads to a reduction of the voltage loss expressed as E-g/q-V-oc. This, in turn, leads to higher device efficiencies as compared to similar CIGS devices without Ag. We report V-oc at 814 mV at a conversion efficiency of 21% for our best ACIGS device with 20% of the group I element consisting of silver. Comparing ACIGS and CIGS devices with the same Ga/(Ga+ In) ratio, the ACIGS devices exhibit about 0.05 eV higher bandgap. Alkali postdeposition treatment with KF leads to improvements in efficiency both for CIGS and ACIGS, but we find that the dose of KF needed for optimum device for ACIGS is 10-20% of the dose used for CIGS.
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| 10. |
- Forsgren, Johan, et al.
(författare)
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Formation and adhesion of biomimetic hydroxyapatite deposited on titanium substrates
- 2007
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Ingår i: Acta Biomaterialia. - : Elsevier BV. - 1742-7061. ; 3:6, s. 980-984
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Tidskriftsartikel (refereegranskat)abstract
- This study has been carried out to investigate the bioactivity of rutile and to deposit hydroxyapatite (HA) on heat-treated titanium through a biomimetic method. Biomimetic deposition of HA has gained large interest because of its low deposition temperature and good step coverage; however, it demands a substrate with bioactive properties. Commercially pure titanium is not bioactive but it can acquire bioactive properties through various surface treatments. In the present study, titanium plates were heat-treated at 800 °C to achieve rutile TiO2 surfaces. These samples were immersed in a phosphate-buffered saline solution for seven days in order to deposit a HA layer on the surface. The rutile TiO2 surfaces were found to be highly bioactive: after seven days of immersion, a layer of HA several micrometers thick covered the plates. The HA surfaces were confirmed by electron microscopy and X-ray diffraction. A scratch test was used to assess the adhesion of the HA coatings. This is a standard method to provide a measure of the coating-to-substrate adhesion and was found to be a useful method to test the thin HA coatings deposited on the bioactive surfaces. The critical pressure of the layer was estimated to be 2.4 ± 0.1 GPa.
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| 11. |
- Forsgren, Johan, et al.
(författare)
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Structural change of biomimetic hydroxyapatite coatings due to heat treatment
- 2007
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Ingår i: Journal of Applied Biomaterials & Biomechanics. - 1722-6899. ; 5:1, s. 23-27
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Tidskriftsartikel (refereegranskat)abstract
- Biomimetic deposition of hydroxyapatite (HA) coatings on implants could be done for two reasons, one is to study their possible bioactivity, and one is to generate bioactive coatings on implants before implantation surgery to improve the osseointegration. Heat treatment of coated implants can be performed for several reasons, for example, to ensure coating sterility and to increase the adhesion. This paper describes the morphology and crystalline structure changes occurring due to the heat treatment of biomimetic HA coatings on rutile TiO2. Rutile TiO2 surfaces were produced on titanium (Ti) plates by heating at 800 C. Afterwards, these samples were immersed in a phosphate buffer saline solution for 7 days at 37 C in order to deposit HA coatings on their surfaces. These HA coatings were then either untreated or heat treated at 600 or 800 C for 1 hr. The coatings microstructural changes were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cross-sectional TEM samples were produced using a sample preparation method based on focused ion beam microscopy (FIB). Rutile was found to be bioactive due to HA formation on the surface. The 600 C heat treatment of the HA coating changed its morphology, increased its grain size and also increased the porosity. At 800 C the coating was completely transformed to beta-TCP according to XRD. Sample preparation using FIB and TEM analysis proved to be a useful method for high-resolution analysis of biomimetic coatings in cross-section.
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| 13. |
- Heinrichs, Jannica, et al.
(författare)
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In vitro bioactivity of Atomic Layer Deposited titanium dioxide on titanium and silicon substrates
- 2008
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Ingår i: BIOCERAMICS, VOL 20, PTS 1 AND 2. ; , s. 689-692
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Konferensbidrag (refereegranskat)abstract
- A non-bioactive implant device can easily be changed to in vitro bioactive with a thin This crystalline coating can be deposited very thin with great step coating of crystalline TiO2 coverage at a low temperature with Atomic Layer Deposition (ALD). An anatase TiO2 coating was built up atomic layer by atomic layer using TiI4 and H2O as precursors in a hot wall furnace. Several hundreds of cycles resulted in a 10-30nm well defined TiO2 of anatase phase on both Si and Ti substrates. These coatings were shown to be bioactive when immersed in simulated body fluid in vitro, as hydroxyapatite (HA) formed on the surface. The surface roughness of the substrates affected the adhesion of the HA. The adhesion was low on the smooth Si but much better on the 100 times rougher Ti. The ALD technique is promising for coating substrates of all shapes with bioactive crystalline TiO2 at a low temperature.
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- Jarmar, Tobias, 1974-
(författare)
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High-Resolution Studies of Silicide-films for Nano IC-Components
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The function of titanium- and nickel-silicides is to lower the series resistance and contact resistivity in gate, source and drain contacts of an integrated circuit transistor. With decreasing dimensions, the low resistivity C54 TiSi2 is not formed and stays in its high resistivity phase C49. It was found that a layer of niobium interposed between titanium and silicon, which is supposed to promote the C54 phase, led to the formation of the high resistivity C40 (Ti,Nb)Si2 in both small and large contacts. Increased interest in Si1-xGex layers led to the inclusion of the Ni-Si-Ge system in this project. The interaction between nickel and poly-Si0.42Ge0.58 was found to be different from nickel and poly-silicon in the meaning of the phases formed during high temperature annealing. High-resistivity NiSi2 was formed at 750°C, but nickel and Si0.42Ge0.58 formed no disilicide. A massive out-diffusion of germanium from the NiSi1-uGeu resulted in agglomeration at lower temperatures than for NiSi. This was ascribed to the larger enthalpy of formation for nickel reacting with silicon than with germanium. Ternary phase diagrams, with and without the disilicide phase, were calculated. According to the tie lines, NiSi1-uGeu will be in thermodynamic equilibrium with Si1-xGex when u is smaller than x. This was confirmed experimentally, where a balanced germanium concentration in NiSi1-uGeu and Si1-xGex, stabilized the germanosilicide. When nickel interacted with strained and relaxed silicon-germanium it was established that a strained substrate led to a morphologically unstable NiSi1-uGeu. The germanosilicide was highly textured on both (001) and (111) substrates. The texturing was explained by the absence of Ni(SiGe)2 which forced NiSiGe to reorient so as not to resemble a digermanosilicide at the film/substrate interface. NiSi0.82Ge0.18 formed on p+-Si0.82Ge0.18 in CBKs grew laterally under the SiO2, defining the contact hole. The contact resistivity extracted by 3D modelling was 5×10-8 Ωcm2.
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| 22. |
- Jarmar, Tobias, et al.
(författare)
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Injectable bone cements for vertebroplasty studied in sheep vertebrae with electron microscopy
- 2008
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Ingår i: Key Engineering Materials. - 1662-9795.
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Tidskriftsartikel (refereegranskat)abstract
- Vertebral compression fractures were simulated by making a hole into sheep vertebrae and by injecting a stabilizing material. The injectable bio-ceramic Xeraspine™ was evaluated together with a commercially available PMMA (Vertebroplastic™) as the reference material. The Vertebrae were harvested after 7 days and prepared for microscopy. The samples were deposited with gold on the surface and thereafter subjected to SEM and EDX analysis. It was found that the Xeraspine-bone interface was composed of a mixture of elements. The Vertebroplastic implant was embedded in a carbon containing tissue, likely a soft tissue capsule. The Xeraspine sample was subjected to high resolution analysis in the TEM combined with EDX measurements. The TEM sample was prepared with a novel technique for preparation of the tissue-material interface (FIB). In the TEM analysis it was found that the interface region consists of ZrO2 together with a mixture possibly consisting of katoite and apatite formed during setting and/or originating from the boneapatite.
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| 25. |
- Larsen, Jes K, et al.
(författare)
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Sulfurization of Co-Evaporated Cu(In,Ga)Se-2 as a Postdeposition Treatment
- 2018
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Ingår i: IEEE Journal of Photovoltaics. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2156-3381 .- 2156-3403. ; 8:2, s. 604-610
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Tidskriftsartikel (refereegranskat)abstract
- It is investigated if the performance of Cu(In,Ga)Se-2 (CIGSe) solar cells produced by co-evaporation can be improved by surface sulfurization in a postdeposition treatment. The expected benefit would be the formation of a sulfur/selenium gradient resulting in reduced interface recombination and increased open-circuit voltage. In the conditions used here it was, however, found that the reaction of the CIGSe layer in a sulfur environment results in the formation of a CuInS2 (CIS) surface phase containing no or very little selenium and gallium. At the same time, a significant pile up of gallium was observed at the CIGSe/CIS boundary. This surface structure was formed for a wide range of annealing conditions investigated in this paper. Increasing the temperature or extending the time of the dwell stage had a similar effect on the material. The gallium enrichment and CIS surface layer widens the surface bandgap and therefore increases the open-circuit voltage. At the same time, the fill factor is reduced, since the interface layer acts as an electron barrier. Due to the balance of these effects, the conversion efficiency could not be improved.
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