| 1. |
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| 2. |
- Aad, G, et al.
(författare)
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- 2015
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swepub:Mat__t
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| 3. |
- Bruzzi, M, et al.
(författare)
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Radiation-hard semiconductor detectors for SuperLHC
- 2005
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 541:1-2, s. 189-201
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Tidskriftsartikel (refereegranskat)abstract
- An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work.
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| 4. |
- Iles, Mark M., et al.
(författare)
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A variant in FTO shows association with melanoma risk not due to BMI
- 2013
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 45:4, s. 428-432
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Tidskriftsartikel (refereegranskat)abstract
- We report the results of an association study of melanoma that is based on the genome-wide imputation of the genotypes of 1,353 cases and 3,566 controls of European origin conducted by the GenoMEL consortium. This revealed an association between several SNPs in intron 8 of the FTO gene, including rs16953002, which replicated using 12,313 cases and 55,667 controls of European ancestry from Europe, the USA and Australia (combined P = 3.6 x 10(-12), per-allele odds ratio for allele A = 1.16). In addition to identifying a new melanomasusceptibility locus, this is to our knowledge the first study to identify and replicate an association with SNPs in FTO not related to body mass index (BMI). These SNPs are not in intron 1 (the BMI-related region) and exhibit no association with BMI. This suggests FTO's function may be broader than the existing paradigm that FTO variants influence multiple traits only through their associations with BMI and obesity.
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| 5. |
- Lang, J. J. K., et al.
(författare)
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Tin-stabilized (1 x 2) and (1 x 4) reconstructions on GaAs(100) and InAs(100) studied by scanning tunneling microscopy, photoelectron spectroscopy, and ab initio calculations
- 2011
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 605:9-10, s. 883-888
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Tidskriftsartikel (refereegranskat)abstract
- Tin (Sn) induced (1 x 2) reconstructions on GaAs(100) and InAs(100) substrates have been studied by low energy electron diffraction (LEED), photoelectron spectroscopy, scanning tunneling microscopy/spectroscopy (STM/STS) and ab initio calculations. The comparison of measured and calculated STM images and surface core-level shifts shows that these surfaces can be well described with the energetically stable building blocks that consist of Sn-III dimers. Furthermore, a new Sn-induced (1 x 4) reconstruction was found. In this reconstruction the occupied dangling bonds are closer to each other than in the more symmetric (1 x 2) reconstruction, and it is shown that the (1 x 4) reconstruction is stabilized as the adatom size increases.
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| 6. |
- Lang, J. J. K., et al.
(författare)
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Unveiling and controlling the electronic structure of oxidized semiconductor surfaces: Crystalline oxidized InSb(100)(1 x 2)-O
- 2014
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 90:4
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Tidskriftsartikel (refereegranskat)abstract
- The exothermic nature of oxidation causes nearly all semiconductor applications in various fields like electronics, medicine, photonics, and sensor technology to acquire an oxidized semiconductor surface part during the application manufacturing. The significance of understanding and controlling the atomic scale properties of oxidized semiconductor surfaces is expected to increase even further with the development of nanoscale semiconductor crystals. The nature of oxidized semiconductor layers is, however, hard to predict and characterize as they are usually buried and amorphous. To shed light on these issues, we pursue a different approach based on oxidized III-V semiconductor layers that are crystalline. We present a comprehensive characterization of oxidized crystalline InSb(100)(1 x 2)-O layers by ab initio calculations, photoelectron spectroscopy, scanning tunneling microscopy, and spectroscopy, and demonstrate the electronic band structures of different oxidized phases of the semiconductor, which elucidate the previous contradictory semiconductor-oxidation effects. At 0.5 monolayer (ML) oxidation, oxygen atoms tend to occupy subsurface Sb sites, leading to metallic states in the semiconductor band gap, which arise from top dimers. When the oxidation is increased to the 1.0-2.0 ML concentration, oxygen occupies also interstitial sites, and the insulating band structure without gap states is stabilized with unusual occupied In dangling bonds. In contrast, the 2.5-3.0 ML oxide phases undergo significant changes toward a less ordered structure. The findings suggest a methodology for manipulating the electronic structure of oxidized semiconductor layers.
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| 7. |
- Barrett, Jennifer H., et al.
(författare)
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Genome-wide association study identifies three new melanoma susceptibility loci
- 2011
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Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1546-1718 .- 1061-4036. ; 43:11, s. 1108-1113
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Tidskriftsartikel (refereegranskat)abstract
- We report a genome-wide association study for melanoma that was conducted by the GenoMEL Consortium. Our discovery phase included 2,981 individuals with melanoma and 1,982 study-specific control individuals of European ancestry, as well as an additional 6,426 control subjects from French or British populations, all of whom were genotyped for 317,000 or 610,000 single-nucleotide polymorphisms (SNPs). Our analysis replicated previously known melanoma susceptibility loci. Seven new regions with at least one SNP with P < 10(-5) and further local imputed or genotyped support were selected for replication using two other genome-wide studies (from Australia and Texas, USA). Additional replication came from case-control series from the UK and The Netherlands. Variants at three of the seven loci replicated at P < 10(-3): an SNP in ATM (rs1801516, overall P = 3.4 x 10(-9)), an SNP in MX2 (rs45430, P = 2.9 x 10-9) and an SNP adjacent to CASP8 (rs13016963, P = 8.6 x 10(-10)). A fourth locus near CCND1 remains of potential interest, showing suggestive but inconclusive evidence of replication (rs1485993, overall P = 4.6 x 10(-7) under a fixed-effects model and P = 1.2 x 10(-3) under a random-effects model). These newly associated variants showed no association with nevus or pigmentation phenotypes in a large British case-control series.
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| 8. |
- Laukkanen, P, et al.
(författare)
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Local variation in Bi crystal sites of epitaxial GaAsBi studied by photoelectron spectroscopy and first-principles calculations
- 2017
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 396, s. 688-694
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial Bi-containing III–V crystals (III-V1-xBix) have attracted increasing interest due to their potential in infrared applications. Atomic-scale characterization and engineering of bulk-like III-V1-xBix properties (e.g., Bi incorporation and defect formation) are challenging but relevant to develop applications. Toward that target, we report here that the traditional surface-science measurement of photoelectron spectroscopy (PES) is a potential, non-destructive method to be combined in the studies of bulk-like properties, when surface effects are properly removed. We have investigated epitaxial GaAs1-xBix films, capped by epitaxial AlAs layers, with high-resolution photoelectron spectroscopy. The Bi5d core-level spectra of GaAs1-xBix together with ab-initio calculations give direct evidence of variation of Bi bonding environment in the lattice sites. The result agrees with photoluminescence (PL) measurement which shows that the studied GaAs1-xBix films include local areas with higher Bi content, which contribute to PL but do not readily appear in x-ray diffraction (XRD). The measured and calculated Bi core-level shifts show also that Ga vacancies and Bi clusters are dominant defects.
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| 9. |
- Laukkanen, P., et al.
(författare)
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Ultrathin (1x2)-Sn layer on GaAs(100) and InAs(100) substrates : A catalyst for removal of amorphous surface oxides
- 2011
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 98:23, s. 231908-1-231908-3
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Tidskriftsartikel (refereegranskat)abstract
- Amorphous surface oxides of III-V semiconductors are harmful in many contexts of device development. Using low-energy electron diffraction and photoelectron spectroscopy, we demonstrate that surface oxides formed at Sn-capped GaAs(100) and InAs(100) surfaces in air are effectively removed by heating. This Sn-mediated oxide desorption procedure results in the initial well-defined Sn-stabilized (1x2) surface even for samples exposed to air for a prolonged time. Based on ab initio calculations we propose that the phenomenon is due to indirect and direct effects of Sn. The Sn-induced surface composition weakens oxygen adsorption.
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| 10. |
- Makela, J., et al.
(författare)
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Line shape and composition of the In 3d(5/2) core-level photoemission for the interface analysis of In-containing III-V semiconductors
- 2015
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Ingår i: Applied Surface Science. - : Elsevier BV. - 1873-5584 .- 0169-4332. ; 329, s. 371-375
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Tidskriftsartikel (refereegranskat)abstract
- The In 3d(5/2) photoelectron spectroscopy peak has been widely used to determine the interface structures of In-containing III-V device materials (e.g., oxidation states). However, an unclear parameter affecting the determination of the energy shifts and number of the core-level components, and therefore, the interpreted interface structure and composition, is still the intrinsic In 3d(5/2) peak line shape. It is undecided whether the line shape is naturally symmetric or asymmetric for pure In-containing III-V compounds. By using high-resolution photoelectron spectroscopy, we show that the In 3d(5/2) asymmetry arising from the emission at high binding-energy tail is not an intrinsic property of InAs, InP, InSb and InGaAs. Furthermore, it is shown that asymmetry of In 3d(5/2) peaks of pure III-V's originates from the natural surface reconstructions which cause the coexistence of slightly shifted In 3d(5/2) components with the symmetric peak shape and dominant Lorentzian broadening. (C) 2015 Elsevier B.V. All rights reserved.
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| 11. |
- Punkkinen, Marko Patrick John, et al.
(författare)
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Oxidized In-containing III-V(100) surfaces : Formation of crystalline oxide films and semiconductor-oxide interfaces
- 2011
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:19, s. 195329-
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Tidskriftsartikel (refereegranskat)abstract
- Previously found oxidized III-V semiconductor surfaces have been generally structurally disordered and useless for applications. We disclose a family of well-ordered oxidized InAs, InGaAs, InP, and InSb surfaces found by experiments. The found epitaxial oxide-III-V interface is insulating and free of defects related to the harmful Fermi-level pinning, which opens up new possibilities to develop long-sought III-V metal-oxide-semiconductor transistors. Calculations reveal that the early stages in the oxidation process include only O-III bonds due to the geometry of the III-V(100)c(8 x 2) substrate, which is responsible for the formation of the ordered interface. The found surfaces provide a different platform to study the oxidation and properties of oxides, e. g., the origins of the photoemission shifts and electronic structures, using surface science methods.
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| 12. |
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| 13. |
- Kuzmin, M., et al.
(författare)
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Surface core-level shifts on Ge(111)c(2 x 8) : Experiment and theory
- 2011
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 83:24, s. 245319-
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Tidskriftsartikel (refereegranskat)abstract
- Combining high-resolution photoelectron spectroscopy and density functional theory (DFT) calculations, 3d photoemission line shape and surface core-level shifts have been reinvestigated on the Ge(111)c(2 x 8) surface. It is found that 3d spectra include, in addition to the bulk and three surface-shifted components reported in literature, a component that was not identified in earlier measurements with a lower resolution. The detailed interpretation of these spectra and their line shape is made on the basis of DFT calculations. It is shown that the lowest binding energy component is due to the rest atoms. The higher binding energy emission is caused by the adatoms and the third-layer atoms that are below the adatoms. Finally, the two other surface components originate from the first- and second-layer atoms. The screening effects in the Ge(111)c(2 x 8) are discussed.
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| 14. |
- Lang, J. J. K., et al.
(författare)
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Ab initio and scanning tunneling microscopy study of an indium-terminated GaAs(100) surface : An indium-induced surface reconstruction change in the c(8x2) structure
- 2010
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:24, s. 245305-
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Tidskriftsartikel (refereegranskat)abstract
- Technologically useful indium- (In) terminated c(8 x 2)-reconstructed GaAs(100) substrate surface has been studied by first-principles calculations and scanning tunneling microscopy (STM) measurements. Our total-energy calculations demonstrate the stability of four different so-called zeta a structures with In monomer rows and In coverage between 0.5 and 2 monolayers on the GaAs(100) substrate. Thus, we introduce a surface system, which stabilizes the zeta a reconstruction. Furthermore, an interesting trend is found. Atomic structure of the c(8 x 2) reconstruction depends on the surface-layer cation and substrate volumes, which, in principle, allows to tune the surface structure by cation adsorption. This phenomenon is related to the peculiar c(8 x 2) atomic surface structure, which shows mixed surface layer, including both anions and cations, and uncommon metallic-type cations in the zeta a structure, which do not show covalent bonds. Our results predict a structural transition from the zeta structure to the zeta a structure as the surface cation size is increased at 0 K. The found transition is probably related to the disordered surface structures (consisting of zeta and zeta a building blocks) found experimentally by x-ray diffraction at room temperature. Comparison of the STM images, calculated for various c(8 x 2) models, with the former and present measured STM images of In/GaAs(100) c(8 x 2) supports the presence of stable zeta a reconstructions.
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| 15. |
- Punkkinen, M. P. J., et al.
(författare)
-
Does Bi form clusters in GaAs1-xBix alloys?
- 2014
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Ingår i: Semiconductor Science and Technology. - : IOP Publishing. - 0268-1242 .- 1361-6641. ; 29:11, s. 115007-
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Tidskriftsartikel (refereegranskat)abstract
- GaAs1 - xBix alloys attract significant interest due to their potentiality for several applications, including solar cells. Recent experiments link the crucial optical properties of these alloys to Bi clustering at certain Bi compositions. Using ab initio calculations, we show that there is no thermodynamical driving force for the formation of small GaBi clusters incorporating As substitutional sites. However, the Ga vacancies should gather Bi atoms leading to small Bi clusters, and the Ga vacancies can act as nucleation centers for phase separation. The formation energy of the GaAs1 - xBix with respect to GaAs and GaBi shows a maximum at intermediate Bi concentrations. Thermodynamics and kinetics of the GaAs1 - xBix film growth is discussed. High Bi solubility is obtained, if the Bi atoms on the energetically favorable atom positions in the subsurface layer are relatively frozen. The Ga vacancy concentration may be increased by the incorporation of Bi. The Bi atoms can also prevent the out diffusion of Ga vacancies.
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| 16. |
- Punkkinen, M. P. J., et al.
(författare)
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Thermodynamics of the pseudobinary GaAs1-xBix (0 ≤ x ≤ 1) alloys studied by different exchange-correlation functionals, special quasi-random structures and Monte Carlo simulations
- 2015
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Ingår i: Computational Condensed Matter. - : Elsevier. - 2352-2143. ; 5, s. 7-13
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Tidskriftsartikel (refereegranskat)abstract
- GaAs1-xBix alloys have useful properties for many optoelectronic applications. Although the crystal growth by molecular beam epitaxy is influenced by kinetics, it is also important to understand the thermodynamics of the alloys. The Gibbs formation energies and the immiscibility curve of the totally disordered GaAs1-xBix (0 ≤ x ≤ 1) are determined using special quasi-random structures (SQS) of different sizes, different exchange-correlation functionals and Monte Carlo simulations. The local density approximation gives slightly larger mixing enthalpies and smaller Bi solubilities than the generalized gradient approximation for the GaAs1-xBix alloys, if the semiconducting GaAs and metallic Ga and Bi are reference states. The 64 and 512 atom SQS give similar mixing enthalpies, except at x = 0.5, where as eight atom SQS overestimate the mixing enthalpy significantly. The disordered alloys are more stable than the most stable ordered phases except at very low temperatures. The spinodal transformation temperature corresponds approximately to the latest experimental results, if the separated systems can conform to their own lattice constants. The spinodal transformation temperature is decreased very significantly, if the decomposing phases are constrained to maintain lattice coherence with the substrate. The strain energies of the alloys and decomposing phases are large also at the surfaces.
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| 17. |
- Tuominen, M., et al.
(författare)
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Oxidized crystalline (3 x 1)-O surface phases of InAs and InSb studied by high-resolution photoelectron spectroscopy
- 2015
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 106:1
-
Tidskriftsartikel (refereegranskat)abstract
- The pre-oxidized crystalline (3 x 1)-O structure of InAs(100) has been recently found to significantly improve insulator/InAs junctions for devices, but the atomic structure and formation of this useful oxide layer are not well understood. We report high-resolution photoelectron spectroscopy analysis of (3 x 1)-O on InAs(100) and InSb(100). The findings reveal that the atomic structure of (3 x 1)-O consists of In atoms with unexpected negative (between -0.64 and -0.47 eV) and only moderate positive (In2O type) core-level shifts; highly oxidized group-V sites; and four different oxygen sites. These fingerprint shifts are compared to those of previously studied oxides of III-V to elucidate oxidation processes. (C) 2015 AIP Publishing LLC.
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| 18. |
- Kuzmin, M., et al.
(författare)
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Atomic structure of Yb/Si(100)(2X6) : Interrelation between the silicon dimer arrangement and Si 2p photoemission line shape
- 2010
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:11, s. 113302-
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Tidskriftsartikel (refereegranskat)abstract
- Combining photoelectron spectroscopy and density-functional theory calculations, we have studied the atomic geometry of Yb/Si(100)(2 X 6) reconstruction and the mechanisms responsible for its stabilization as well as the influence of this reconstruction on Si 2p core-level photoemission. The analysis of measured and calculated surface core-level shifts supports the recently proposed model of the Yb/Si(100)(2 X 6). It involves, in agreement with valence-band measurements, unbuckled (symmetrical) silicon dimers, leading to unusually narrowed Si 2p line shape as compared to those of related systems. The origin of the symmetrical dimers in the (2 X 6) structure is discussed in the context of previous results in literature.
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| 19. |
- Kuzmin, M., et al.
(författare)
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Dimer-T(3) reconstruction of the Sm/Si(100)(2 x 3) surface studied by high-resolution photoelectron spectroscopy and density functional theory calculations
- 2011
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:24, s. 245322-
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Tidskriftsartikel (refereegranskat)abstract
- Silicon dimer-containing reconstructions on Si(100) can be induced by submonolayer amounts of rare earth (RE) metals. The tilt of dimer bonds in such reconstructions can be controlled by the coverage and electronic properties of RE adsorbates. In this study, we have utilized improved high-resolution photoelectron spectroscopy with the synchrotron radiation and density functional theory (DFT) calculations to exploit the structural and electronic properties of the Sm/Si(100)(2 x 3) system. A careful analysis of photoelectron spectra, in combination with DFT calculations of surface core-level shifts for silicon atoms in energetically plausible structural models, has allowed us to establish the favorable atomic configuration of Sm/Si(100)(2 x 3) with a buckled Si dimer and to explain characteristic features of Si 2p line shape in detail. It is shown that the dimer buckling leads to a significant core-level binding-energy splitting of the first-layer Si atoms, affecting the lower-binding-energy region of Si 2p spectra drastically. An interpretation of the Si 2p line shape for RE/Si(100)(2 x 3) that is based on combined initial state and complete screening data is suggested. The mechanism underlying the buckling and symmetrization of silicon dimers in RE/Si(100) reconstructions is discussed.
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| 20. |
- Laukkanen, P., et al.
(författare)
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Formation and destabilization of Ga interstitials in GaAsN : Experiment and theory
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:19, s. 195205-
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Tidskriftsartikel (refereegranskat)abstract
- Using first-principles total energy calculations we have found complex defects induced by N incorporation in GaAsN. The formation energy of the Ga interstitial atom is very significantly decreased due to local effects within the defect complex. The stability of the Ga interstitials is further increased at surfaces. The present results suggest that the energetically favorable Ga interstitial atoms are much more abundant in GaAsN than the previously considered N defects, which have relatively large formation energies. Our synchrotron radiation core-level photoemission measurements support the computational results. The formation of harmful Ga interstitials should be reduced by incorporating large group IV B atoms in GaAsN.
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| 21. |
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| 22. |
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Ejenstam, Lina, 1985-, et al.
(författare)
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Long-term corrosion protection by a thin nano-composite coating
- 2015
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 357:Part B, s. 2333-2342
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Tidskriftsartikel (refereegranskat)abstract
- We report and discuss the corrosion protective properties of a thin nano-composite coating system consisting of an 11μm thick polyester acrylate (PEA) basecoat, covered by an approximately 1-2μm thick layer of TiO2 nanoparticles carrying a 0.05μm thick hexamethyl disiloxane (HMDSO) top coat. The corrosion protective properties were evaluated on carbon steel substrates immersed in 3wt% NaCl solution by open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) measurements. The protective properties of each layer, and of each pair of layers, were also evaluated to gain further understanding of the long-term protective properties offered by the nano-composite coating. The full coating system showed excellent corrosion protective properties in the corrosive environment of 3wt% NaCl-solution for an extended period of 100 days, during which the coating impedance, at the lower frequency limit (0.01Hz), remained above 108 Ωcm2. We suggest that the excellent corrosion protective properties of the complete coating system is due to a combination of (i) good adhesion and stability of the PEA basecoat, (ii) the surface roughness and the elongated diffusion path provided by the addition of TiO2 nanoparticles, and (iii) the low surface energy provided by the HMDSO top coat.
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| 27. |
- Eriksson, Mimmi, et al.
(författare)
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Effects of Gas Layer Thickness on Capillary Interactions at Superhydrophobic Surfaces
- 2024
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 40:9, s. 4801-4810
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Tidskriftsartikel (refereegranskat)abstract
- Strongly attractive forces act between superhydrophobic surfaces across water due to the formation of a bridging gas capillary. Upon separation, the attraction can range up to tens of micrometers as the gas capillary grows, while gas molecules accumulate in the capillary. We argue that most of these molecules come from the pre-existing gaseous layer found at and within the superhydrophobic coating. In this study, we investigate how the capillary size and the resulting capillary forces are affected by the thickness of the gaseous layer. To this end, we prepared superhydrophobic coatings with different thicknesses by utilizing different numbers of coating cycles of a liquid flame spraying technique. Laser scanning confocal microscopy confirmed an increase in gas layer thickness with an increasing number of coating cycles. Force measurements between such coatings and a hydrophobic colloidal probe revealed attractive forces caused by bridging gas capillaries, and both the capillary size and the range of attraction increased with increasing thickness of the pre-existing gas layer. Hence, our data suggest that the amount of available gas at and in the superhydrophobic coating determines the force range and capillary growth.
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| 28. |
- Eriksson, Mimmi, et al.
(författare)
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Effects of liquid surface tension on gas capillaries and capillary forces at superamphiphobic surfaces
- 2023
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- The formation of a bridging gas capillary between superhydrophobic surfaces in water gives rise to strongly attractive interactions ranging up to several micrometers on separation. However, most liquids used in materials research are oil-based or contain surfactants. Superamphiphobic surfaces repel both water and low-surface-tension liquids. To control the interactions between a superamphiphobic surface and a particle, it needs to be resolved whether and how gas capillaries form in non-polar and low-surface-tension liquids. Such insight will aid advanced functional materials development. Here, we combine laser scanning confocal imaging and colloidal probe atomic force microscopy to elucidate the interaction between a superamphiphobic surface and a hydrophobic microparticle in three liquids with different surface tensions: water (73 mN m−1), ethylene glycol (48 mN m−1) and hexadecane (27 mN m−1). We show that bridging gas capillaries are formed in all three liquids. Force-distance curves between the superamphiphobic surface and the particle reveal strong attractive interactions, where the range and magnitude decrease with liquid surface tension. Comparison of free energy calculations based on the capillary menisci shapes and the force measurements suggest that under our dynamic measurements the gas pressure in the capillary is slightly below ambient.
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| 29. |
- Ferreira, Ana R. V., et al.
(författare)
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Comparison of different coating techniques on the properties of FucoPol films
- 2017
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Ingår i: International Journal of Biological Macromolecules. - : Elsevier BV. - 0141-8130 .- 1879-0003. ; 103, s. 268-274
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Tidskriftsartikel (refereegranskat)abstract
- Plasma deposition, liquid flame spray (LFS) and atomic layer deposition (ALD) were used to form inorganic coatings in new exopolysaccharide (FucoPol) biodegradable films. Coated films were characterised in terms of surface, optical and barrier properties in order to evaluate their potential use in food packaging. FucoPol films presented dense and homogeneous surface with instant water contact angle of 95̊. Plasma deposition of perfluorohexane (PFH) on FucoPol surface has not shown significant improvement in the hydrophobic behaviour over the time. The FucoPol coating of SiO2 nanoparticles deposited by LFS and plasma deposition of PFH have shown higher instant water contact angle (135°) caused by coating surface roughness, but this hydrophobic behaviour was not stable over time. FucoPol films coated only with TiO2 deposited by ALD and combination of that with plasma deposition of PFH have shown stable water contact angle during time (90̊ and 115̊, respectively), transparency in the same order of magnitude and significantly lower permeability to water vapour (3.45 × 10−11 mol/m s Pa and 3.45 × 10−11 mol/m s Pa when compared to uncoated films with 5.32 × 10−11 mol/m s Pa). Moreover, films coated with TiO2-PFH have also shown a permeability to oxygen of 1.70 × 10−16 molm/m2s Pa which is 67% lower than uncoated films.
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| 30. |
- Hackman, T., et al.
(författare)
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Doppler images of II Pegasi for 2004-2010
- 2012
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 538, s. A126-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We study the spot activity of II Peg during the years 2004-2010 to determine long- and short-term changes in the magnetic activity. In a previous study, we detected a persistent active longitude, as well as major changes in the spot configuration occurring on a timescale of shorter than a year. The main objective of this study is to determine whether the same phenomena persist in the star during these six years of spectroscopic monitoring. Methods. The observations were collected with the high-resolution SOFIN spectrograph at the Nordic Optical Telescope. The temperature maps were calculated using a Doppler imaging code based on Tikhonov regularization. Results. We present 12 new temperature maps that show spots distributed mainly over high and intermediate latitudes. In each image, 1-3 main active regions can be identified. The activity level of the star is clearly lower than during our previous study for the years 1994-2002. In contrast to the previous observations, we detect no clear drift of the active regions with respect to the rotation of the star. Conclusions. Having shown a systematic longitudinal drift of the spot-generating mechanism during 1994-2002, the star has clearly switched to a low-activity state for 2004-2010, during which the spot locations appear more random over phase space. It could be that the star is near to a minimum of its activity cycle.
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| 31. |
- Hackman, T., et al.
(författare)
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Spot activity of II Peg
- 2011
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Ingår i: Astronomical Notes - Astronomische Nachrichten. - : Wiley. - 0004-6337 .- 1521-3994. ; 332:9-10, s. 859-865
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the long-term spot activity of the RS CVn star II Peg by means of Doppler imaging based on spectroscopy and time series analysis of photometry. We present 28 Doppler imaging temperature maps spanning the years 1994-2010, of which 14 were calculated for the present study. The longitudinal spot distribution, derived from the surface temperature maps, is compared with epochs of the light curve minima, derived from photometric observations. We detect a longitudinal drift in the major spot structure during 1995-2003. After this there is a clear decrease in the activity level and no clear drift can be seen. We conclude that the variations could be caused by a cyclic behaviour of the underlying magnetic dynamo.
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| 32. |
- Heydari, Golrokh, et al.
(författare)
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Wetting hysteresis induced by temperature changes : Supercooled water on hydrophobic surfaces
- 2016
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Ingår i: Journal of Colloid and Interface Science. - : Academic Press. - 0021-9797 .- 1095-7103. ; 468, s. 21-33
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Tidskriftsartikel (refereegranskat)abstract
- The state and stability of supercooled water on (super)hydrophobic surfaces is crucial for low temperature applications and it will affect anti-icing and de-icing properties. Surface characteristics such as topography and chemistry are expected to affect wetting hysteresis during temperature cycling experiments, and also the freezing delay of supercooled water. We utilized stochastically rough wood surfaces that were further modified to render them hydrophobic or superhydrophobic. Liquid flame spraying (LFS) was utilized to create a multi-scale roughness by depositing titanium dioxide nanoparticles. The coating was subsequently made non-polar by applying a thin plasma polymer layer. As flat reference samples modified silica surfaces with similar chemistries were utilized. With these substrates we test the hypothesis that superhydrophobic surfaces also should retard ice formation. Wetting hysteresis was evaluated using contact angle measurements during a freeze-thaw cycle from room temperature to freezing occurrence at -7 °C, and then back to room temperature. Further, the delay in freezing of supercooled water droplets was studied at temperatures of -4 °C and -7 °C. The hysteresis in contact angle observed during a cooling-heating cycle is found to be small on flat hydrophobic surfaces. However, significant changes in contact angles during a cooling-heating cycle are observed on the rough surfaces, with a higher contact angle observed on cooling compared to during the subsequent heating. Condensation and subsequent frost formation at sub-zero temperatures induce the hysteresis. The freezing delay data show that the flat surface is more efficient in enhancing the freezing delay than the rougher surfaces, which can be rationalized considering heterogeneous nucleation theory. Thus, our data suggests that molecular flat surfaces, rather than rough superhydrophobic surfaces, are beneficial for retarding ice formation under conditions that allow condensation and frost formation to occur.
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| 33. |
- Kaplan, Alexander, et al.
(författare)
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Stress raising in laser clad components depending on geometry and defects
- 2013
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Ingår i: 14th NOLAMP Conference. - Luleå : Luleå tekniska universitet. - 9789174396881 - 9789174396898 ; , s. 281-292
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The fatigue life of laser clad components is basically determined by stress raisers, which arehere studied by Finite Element Analysis. Cylindrical and square section bars are compared foraxial, bending and torsional load conditions, which induces the macro-stress field withcorresponding stress peaks. Defects from laser cladding such as pores, cracks or the surfaceroughness superimpose additional stress raising action on this stress field. The geometricalposition and orientation of the defects has strong impact on the induced maximum stresslevel. For surface pores it is demonstrated by the fractography that their occurrence within acritical azimuthal range can initiate fatigue cracking. The different conditions of samplegeometry, load situations, materials and defects are compared and discussed. In particular,advanced illustration methods are applied for improved and generalized documentation andexplanation of the trends, both qualitatively and quantitatively. Guidelines are presented, inparticular emphasizing critical defects and situations, such as surface pores that are difficult todetect because of inclusions, or pores just underneath the surface that generate particularlyhigh stress.
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| 34. |
- Lindborg, M., et al.
(författare)
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Doppler images of the RS CVn binary II Pegasi during the years 1994-2002
- 2011
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 526:6, s. A44-
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Tidskriftsartikel (refereegranskat)abstract
- Aims. We publish 16 Doppler imaging temperature maps for the years 1994-2002 of the active RS CVn star II Peg. The six maps from 1999-2002 are based on previously unpublished observations. Through Doppler imaging we want to study the spot evolution of the star and in particular compare this with previous results showing a cyclic spot behaviour and persistent, active longitudes. Methods. The observations were collected with the SOFIN spectrograph at the Nordic Optical Telescope. The temperature maps were calculated using a Doppler imaging code based on Tikhonov regularization. Results. During 1994-2001, our results show a consistent trend in the derived longitudes of the principal and secondary temperature minima over time such that the magnetic structure appears to rotate somewhat more rapidly than the orbital period of this close binary. A sudden phase jump in the active region occurred between the observing seasons of 2001 and 2002. No clear trend over time is detected in the derived latitudes of the spots, indicating that the systematic motion could be related to the drift of the spot-generating mechanism rather than to differential rotation. The derived temperature maps are quite similar to the ones obtained earlier with different methods and the main differences occur in the spot latitudes and relative strength of the spot structures. Conclusions. We observe both longitude and latitude shifts in the spot activity of II Peg. However, our results are not consistent with the periodic behaviour presented in previous studies.
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| 35. |
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| 36. |
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| 37. |
- Sedighi Moghaddam, Maziar, et al.
(författare)
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Hydrophobisation of wood surfaces by combining liquid flame spray (LFS) and plasma treatment : Dynamic wetting properties
- 2016
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Ingår i: Holzforschung. - : Walter de Gruyter. - 0018-3830 .- 1437-434X. ; 70:6, s. 527-537
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Tidskriftsartikel (refereegranskat)abstract
- The hydrophilic nature of wood surfaces is a major cause for water uptake and subsequent biological degradation and dimensional changes. In the present paper, a thin transparent superhydrophobic layer on pine veneer surfaces has been created for controlling surface wettability and water repellency. This effect was achieved by means of the liquid flame spray (LFS) technique, in the course of which the nanoparticulate titanium dioxide (TiO2) was brought to the surface, followed by plasma polymerisation. Plasma polymerised perfluorohexane (PFH) or hexamethyldisiloxane (HMDSO) were then deposited onto the LFS-treated wood surfaces. The same treatment systems were applied to silicon wafers so as to have well-defined reference surfaces. The dynamic wettability was studied by the multicycle Wilhelmy plate (mWP) method, resulting in advancing and receding contact angles as well as sorption behavior of the samples during repeated wetting cycles in water. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were employed to characterise the topography and surface chemical compositions and to elucidate the question how the morphology of the nanoparticles and plasma affect the wetting behavior. A multi-scale roughness (micro-nano roughness) was found and this enhanced the forced wetting durability via a superhydrophobic effect on the surface, which was stable even after repeated wetting cycles. The hydrophobic effect of this approach was higher compared to that of plasma modified surfaces with their micro-scale modification.
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| 38. |
- Syväjärvi, Mikael, et al.
(författare)
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Growth of 6H and 4H-SiC by sublimation epitaxy
- 1999
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 197:1-2, s. 155-162
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Tidskriftsartikel (refereegranskat)abstract
- The epitaxial sublimation growth process of SiC has been investigated. Layers with specular surfaces and growth rates up to 2 mm/h have been obtained. No step bunching is observed by optical microscopy even on very thick layers which indicates a stable step growth mechanism. Under certain growth conditions the morphology degrades. The morphological stability is investigated and discussed in relation to the growth kinetics. Impurities in the epitaxial layers are investigated by secondary ion mass spectroscopy and low-temperature photoluminescence. The carrier concentration is measured by capacitance–voltage measurements. The structural quality of the grown material is improved compared to the substrate as shown by X-ray diffraction measurements.
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| 39. |
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| 40. |
- Tuominen, M., et al.
(författare)
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Investigation of domain evolution in sublimation epitaxy of SiC
- 1998
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 193:1-2, s. 101-108
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Tidskriftsartikel (refereegranskat)abstract
- High resolution X-ray diffractometry has been applied to study domain misorientation in SiC epi-layers grown by the sublimation epitaxy method. A pronounced effect of the growth conditions on the mosaicity of the epi-layer has been observed. The results are discussed in terms of domain evolution and structural changes during the epi-growth under different growth conditions.
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| 41. |
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| 42. |
- Wu, D., et al.
(författare)
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A novel strained Si0.7Ge0.3 surface-channel pMOSFET with an ALD TiN/Al2O3/HfAlOx/Al2O3 gate stack
- 2003
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 24:3, s. 171-173
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Tidskriftsartikel (refereegranskat)abstract
- Proof-of-concept pMOSFETs with a strained-Si0.7Ge0.3 surface-channel deposited by selective epitaxy and a TiN/Al2O3/HfAIO(x)/Al2O3 gate stack grown by atomic layer chemical vapor deposition (ALD) techniques were fabricated. The Si0.7Ge0.3 pMOSFETs exhibited more than 30% higher current drive and peak transconductance than reference Si pMOSFETs with the same gate stack. The effective mobility for the Si reference coincided with the universal hole mobility curve for Si. The presence of a relatively low density of interface states, determined as 3.3x10(11) cm(-2) eV(-1), yielded a subthreshold slope of 75 mV/dec. for the Si reference. For the Si0.7Ge0.3 pMOSFETs, these values were 1.6x10(12) cm(-2) eV(-1) and 110 mV/dec., respectively.
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| 43. |
- Wu, D., et al.
(författare)
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Ni-salicided CMOS with a poly-SiGe/Al2O3/HfO2/Al2O3 gate stack
- 2005
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 77:1, s. 36-41
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Tidskriftsartikel (refereegranskat)abstract
- Ni-salicided MOSFETs with a gate stack of ALD Al2O3/HfO2/Al2O3 high-x dielectric and poly-SiGe gate electrode were fabricated. The Si pMOSFETs with an EOT of 1.7 nm showed an expected gate leakage current reduction compared to SiO2 with the same EOT and a mobility around 20% lower than the universal curve. The strained SiGe surface-channel pMOSFETs with the same gate stack showed an enhanced current drive and hole mobility. The Si nMOSFETs, however, exhibited a degraded subthreshold slope and a lower current drive even compared with the Si pMOSFETs. Possible reasons for the degradation of Si nMOSFETs were discussed.
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| 44. |
- Aromaa, Mikko, et al.
(författare)
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Atmospheric synthesis of superhydrophobic TiO2 nanoparticle deposits in a single step using Liquid Flame Spray
- 2012
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Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502. ; 52, s. 57-68
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Tidskriftsartikel (refereegranskat)abstract
- Titanium dioxide nanoparticles are synthesised in aerosol phase using the Liquid Flame Spray method. The particles are deposited in-situ on paperboard, glass and metal surfaces. According to literature, titanium dioxide is supposed to be hydrophilic. However, hydrophobic behaviour is observed on paperboard substrates but not on metal or glass substrates. Here, the water contact angle behaviour of the deposits is studied along with XRD, XPS, BET and HR-TEM. The deposits are compared with silicon dioxide deposits having, as expected, hydrophilic properties synthesised with the same method. It seems probable that the deposition process combusts some substrate material from the paperboard substrate, which later on condenses on top of the deposit to form a carbonaceous layer causing the hydrophobic behaviour of the TiO2 deposit. The similar layer does not form when depositing the nanoparticles on a metal or glass surfaces. The observations are more than purely aerosol phenomena. However, they are quite essential in nanoparticle deposition from the aerosol phase onto a substrate which is commonly utilised. (C) 2012 Elsevier Ltd. All rights reserved.
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| 45. |
- Azimi, A, et al.
(författare)
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Silencing FLI or targeting CD13/ANPEP lead to dephosphorylation of EPHA2, a mediator of BRAF inhibitor resistance, and induce growth arrest or apoptosis in melanoma cells
- 2017
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Ingår i: Cell death & disease. - : Springer Science and Business Media LLC. - 2041-4889. ; 8:8, s. e3029-
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Tidskriftsartikel (refereegranskat)abstract
- A majority of patients with BRAF-mutated metastatic melanoma respond to therapy with BRAF inhibitors (BRAFi), but relapses are common owing to acquired resistance. To unravel BRAFi resistance mechanisms we have performed gene expression and mass spectrometry based proteome profiling of the sensitive parental A375 BRAF V600E-mutated human melanoma cell line and of daughter cell lines with induced BRAFi resistance. Increased expression of two novel resistance candidates, aminopeptidase-N (CD13/ANPEP) and ETS transcription factor FLI1 was observed in the BRAFi-resistant daughter cell lines. In addition, increased levels of the previously reported resistance mediators, receptor tyrosine kinase ephrine receptor A2 (EPHA2) and the hepatocyte growth factor receptor MET were also identified. The expression of these proteins was assessed in matched tumor samples from melanoma patients obtained before BRAFi and after disease progression. MET was overexpressed in all progression samples while the expression of the other candidates varied between the individual patients. Targeting CD13/ANPEP by a blocking antibody induced apoptosis in both parental A375- and BRAFi-resistant daughter cells as well as in melanoma cells with intrinsic BRAFi resistance and led to dephosphorylation of EPHA2 on S897, previously demonstrated to cause inhibition of the migratory capacity. AKT and RSK, both reported to induce EPHA2 S897 phosphorylation, were also dephosphorylated after inhibition of CD13/ANPEP. FLI1 silencing also caused decreases in EPHA2 S897 phosphorylation and in total MET protein expression. In addition, silencing of FLI1 sensitized the resistant cells to BRAFi. Furthermore, we show that BRAFi in combination with the multi kinase inhibitor dasatinib can abrogate BRAFi resistance and decrease both EPHA2 S897 phosphorylation and total FLI1 protein expression. This is the first report presenting CD13/ANPEP and FLI1 as important mediators of resistance to BRAF inhibition with potential as drug targets in BRAFi refractory melanoma.
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| 46. |
- Das, I, et al.
(författare)
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Combining ERBB family and MET inhibitors is an effective therapeutic strategy in cutaneous malignant melanoma independent of BRAF/NRAS mutation status
- 2019
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Ingår i: Cell death & disease. - : Springer Science and Business Media LLC. - 2041-4889. ; 10:9, s. 663-
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Tidskriftsartikel (refereegranskat)abstract
- Current treatment modalities for disseminated cutaneous malignant melanoma (CMM) improve survival; however, relapses are common. A number of receptor tyrosine kinases (RTKs) including EGFR and MET have been reported to be involved in CMM metastasis and in the development of resistance to therapy, targeting the mitogen-activated protein kinase (MAPK pathway). IHC analysis showed that patients with higher MET protein expression had a significantly shorter overall survival. In addition, silencing of MET caused an upregulation of EGFR and p-AKT, which was abrogated by concomitant silencing of MET and EGFR in CMM cells resistant to MAPK-targeting drugs. We therefore explored novel treatment strategies using clinically approved drugs afatinib (ERBB family inhibitor) and crizotinib (MET inhibitor), to simultaneously block MET and ERBB family RTKs. The effects of the combination were assessed in cell culture and spheroid models using established CMM and patient-derived short-term cell lines, and an in vivo xenograft mouse model. The combination had a synergistic effect, promoting cell death, concomitant with a potent downregulation of migratory and invasive capacity independent of their BRAF/NRAS mutational status. Furthermore, the combination attenuated tumor growth rate, as ascertained by the significant reduction of Ki67 expression and induced DNA damage in vivo. Importantly, this combination therapy had minimal therapy-related toxicity in mice. Lastly, the cell cycle G2 checkpoint kinase WEE1 and the RTK IGF1R, non-canonical targets, were altered upon exposure to the combination. Knockdown of WEE1 abrogated the combination-mediated effects on cell migration and proliferation in BRAF mutant BRAF inhibitor-sensitive cells, whereas WEE1 silencing alone inhibited cell migration in NRAS mutant cells. In summary, our results show that afatinib and crizotinib in combination is a promising alternative targeted therapy option for CMM patients, irrespective of BRAF/NRAS mutational status, as well as for cases where resistance has developed towards BRAF inhibitors.
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| 47. |
- Eriksson, Mimmi, et al.
(författare)
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Direct Observation of Gas Meniscus Formation on a Superhydrophobic Surface
- 2019
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 13:2, s. 2246-2252
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Tidskriftsartikel (refereegranskat)abstract
- The formation of a bridging gas meniscus via cavitation or nanobubbles is considered the most likely origin of the submicrometer long-range attractive forces measured between hydrophobic surfaces in aqueous solution. However, the dynamics of the formation and evolution of the gas meniscus is still under debate, in particular, in the presence of a thin air layer on a superhydrophobic surface. On superhydrophobic surfaces the range can even exceed 10 μm. Here, we report microscopic images of the formation and growth of a gas meniscus during force measurements between a superhydrophobic surface and a hydrophobic microsphere immersed in water. This is achieved by combining laser scanning confocal microscopy and colloidal probe atomic force microscopy. The configuration allows determination of the volume and shape of the meniscus, together with direct calculation of the Young-Laplace capillary pressure. The long-range attractive interactions acting on separation are due to meniscus formation and volume growth as air is transported from the surface layer.
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| 48. |
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| 49. |
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| 50. |
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