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Repository of the University of Hasselt containing publications in the fields of statistics, computer science, information strategies and material from the Institute for behavioural sciences.

Academic Bibliography

Mostrando recursos 1 - 20 de 184

  1. Semiconducting to metallic-like boron doping of nanocrystalline diamond films and its effect on osteoblastic cells

    Kromka, Alexander; Grausova, Lubica; Bacakova, Lucie; Vacik, Jiri; Rezek, Bohuslav; Vanecek, Milan; WILLIAMS, Oliver; HAENEN, Ken
    The impact of boron doping level of nanocrystalline diamond (NCD) films on the character of cell growth (i.e., adhesion, proliferation and differentiation) is presented. Intrinsic and boron-doped NCD films were grown on Si/SiO2 substrates by microwave plasma CVD process. The boron-doped samples were grown by adding trimethylboron JMB) to the gas mixture of methane and hydrogen. Highly resistive (0 ppm), semiconducting (133 or 1000 ppm), and metallic-like (6700 ppm) NCD films were tested as the artificial substrates for the cultivation of osteoblast-like MG 63 cells. The conductivity and surface charge increased monotonically with the increasing boron content. All NCD substrates...

  2. Increasing the mean grain size in copper films and features

    VANSTREELS, Kris; Brongersma, S.H.; Tokei, Zs.; Carbonell, L; DE CEUNINCK, Ward; D'HAEN, Jan; D'OLIESLAEGER, Marc
    A new grain-growth mode is observed in thick sputtered copper films. This new grain-growth mode, also referred to in this work as super secondary grain growth (SSGG) leads to highly concentric grain growth with grain diameters of many tens of micrometers, and drives the system toward a {100} texture. The appearance, growth dynamics, final grain size, and self-annealing time of this new grain-growth mode strongly depends on the applied bias voltage during deposition of these sputtered films, the film thickness, the post-deposition annealing temperature, and the properties of the copper diffusion barrier layers used in this work. Moreover, a clear...

  3. A new method for the lifetime determination of submicron metal interconnects by means of a parallel test structure

    VANSTREELS, Kris; D'OLIESLAEGER, Marc; DE CEUNINCK, Ward; D'HAEN, Jan; Maex, Karen
    Simulation experiments on both series and parallel electromigration (EM) test structures were carried out under current (or voltage) stress and further analysed by means of the Total Resistance (TR) analysis and a software package "failure" in order to calculate and to compare the behaviour of both EM test structures. These simulation experiments show that the parallel EM test structure is a correct approach for the determination of the failure time of submicron interconnects, the activation energy and the current density exponent n of the thermally driven process, therefore leading to a very substantial reduction of the number of samples that...

  4. State-of-the-art MDMO-PPV: PCBM bulk hetero-junction organic solar cells: materials, nano-morphology and electro-optical properties.

    MANCA, Jean; MUNTERS, Tom; MARTENS, Tom; BEELEN, Zjef; GORIS, Ludwig; D'HAEN, Jan; D'OLIESLAEGER, Marc; LUTSEN, Laurence; VANDERZANDE, Dirk; De Scherer, L.; HAENEN, Ken; NESLADEK, Milos; GEENS, Joris; Poortmans, J.; Andriessen, Ronn
    Current state-of-the-art bulk hetero-junction organic photovoltaic devices will be discussed based on poly(2-methoxy-5-(3',7'-dimethyl-octyloxy))-p-phenylene vinylene, (MDMO-PPV), as an electron donor and (6,6)-phenyl-C-61-butyric-acid (PCBM) (a soluble C60 derivative) as electron acceptor. A brief review will be provided summarizing recent results on efficiency enhancement and on morphological investigations. A significant increase in power conversion efficiency has been demonstrated for devices based on so-called 'sulphinyl' synthesised MDMO-PPV (eta(AM1.5) = 2.9%) in comparison with devices based on 'Gilch' synthesised MDMO-PPV (eta(AM1.5) = 2.5%). In order to understand the higher efficiency values obtained using a different solvent or a different MDMO-PPV-material, electrical and morphological investigations are...

  5. Increasing the mean grain size in copper films and features

    Vanstreels, Kris
    This thesis discusses the introduction of super grains in both sputtered and electroplated copper films and the implementation of these grains in copper interconnects, whose dimensions vary from the micrometer regime to the nanometer regime. The final chapter summarizes the major results of this research and provides some perspectives for future work. Nowadays, a clear increase in the resistivity of copper interconnect wires is observed for scaled wire geometries. This increase embodies several scattering mechanisms such as surface and grain boundary scattering which contribute to the classic electron-phonon scattering in bulk materials. Finding ways to increase the mean grain size...

  6. Relations between morphology and electro-optical properties of MDMO-PPV:PCBM bulk heterojunction organic solar cells

    MARTENS, Tom

  7. Microstructurele studie van thermisch- en stroomgedreven processen in A1-gebaseerde on-chip interconnecties m.b.v. elektronenmicroscopie

    Cosemans, Patrick Peter
    Vanaf het ontstaan van de geïntegreerde schakelingen (IC's) wordt getracht om een groter aantal functies op steeds minder oppervlakte te combineren. Dit heeft tot gevolg dat niet alleen de componenten steeds kleiner warden maar ook de banen die de verschillende componenten verbinden om tot welbepaalde functies te komen. Deze interconnecties bestaan hoofdzakelijk uit Al vanwege de lage elektrische weerstand, de vlotte toepasbaarheid en de compatibiliteit met Si gebaseerde halfgeleidermaterialen (substraat). Door de banen te versmallen, kwam plaats vrij voor nieuwe componenten. Op een gegeven moment werd het maximum van het aantal componenten op een chip bereikt omdat de interconnecties meer...

  8. Morphological, thermal and electrical characterization of organic photovoltaic blends

    Swinnen, Ann
    The major objective of this thesis was to correlate morphology to the electrical properties of bulk heterojunction solar cells. Since at the beginning of this work P3HT:PCBM solar cells gave the best efficiencies, the focus was on this type of blend. First, an extensive morphology study was needed since it is generally known that morphology influences the properties of bulk heterojunction solar cells. Secondly, the relationship between morphology and electrical properties was still inefficiently known and therefore a few options were explored how to correlate them. First, the P3HT:PCBM blend was studied morphologically with a wide variety of techniques, i.e....

  9. Kwantificatie van hoofdelementen met behulp van moleculaire ionen in secundaire ionen massaspectrometrie

    Vlekken, Johan
    In dit proefschrift, met als ti tel : 'Kwantificatie van hoofdelementen met behulp van moleculaire ionen in Secundaire Ionen Massaspectrometrie ', worden twee technieken voorgesteld en besproken, om de kwantitatieve materiaalkarakterisatie van de Secundaire Ionen Massaspectrometrietechniek (SIMS-techniek) te verbeteren. Het onderzoeksgebied waarbinnen de SIMS-techniek wordt aangewend is vrij breed. De SIMS-techniek is algemeen verspreid binnen de micro-elektronicasector waar kwantitatieve profileringen van zowel onzuiverheids- als doperingselementen uiterst belangrijk zijn. Verder wordt de SIMS-techniek ook meer en meer aangewend in andere sectoren binnen de materiaalwetenschappen waar interfaceverschijnselen een belangrijke rol spelen. De Secundaire Ionen Massa Spectrometrie (SIMS), is een analytische techniek gebaseerd...

  10. Characterization of boron doped diamond epilayers grown in a NIRIM type reactor

    MORTET, Vincent; DAENEN, Michael; Teraji, T.; LAZEA, Andrada; Vorlicek, V.; D'HAEN, Jan; HAENEN, Ken; D'OLIESLAEGER, Marc
    Boron doped diamond layers have been grown on (100) single crystal substrates in a wide range of boron concentration. The boron doped layers have been electrically and optically characterized. Boron doped layers with Hall mobility closes to natural diamond holes mobility have been obtained. The films morphology has been observed by scanning electron microscopy and their purity has been assessed by cathodoluminescence. Fourier Transform Photocurrent spectroscopy results show the evolution of the photo-ionization onset and the excited states as boron concentration in the films increases. (C) 2008 Elsevier B.V. All rights reserved.

  11. Effect of molecular orientation on photovoltaic efficiency and carrier transport in a new semiconducting polymer

    Kazukauskas, V; Pranaitis, M; Sentein, C; Rocha, L; Raimond, P; DUYSSENS, Iris; VAN SEVEREN, Ineke; CLEIJ, Thomas; LUTSEN, Laurence; VANDERZANDE, Dirk
    New functionalized soluble poly (p-phenylene vinylene) derivative bearing polar molecules was designed and synthesized in order to investigate effects of molecular orientation in polymer photovoltaic devices. The active polar molecule is the 4-(N-butyl-N-2-hydroxyethyl)-1- nitro-benzene group. The grafting of the push-pull molecule with a donor/transmitter/acceptor structure, possessing a large ground state dipole moment, enables the molecular orientation by a dc electric field. An internal electric field stored in such system facilitates exciton dissociation and improves charge transport in single-layer devices. In our systems an increase in the external quantum efficiency by a factor of about 1.5 to 2 is estimated. The...

  12. Growth of polycrystalline phosphorous-doped CVD diamond layers

    Lazea, A; MORTET, Vincent; D'HAEN, Jan; Geithner, P.; Ristein, J.; D'OLIESLAEGER, Marc; HAENEN, Ken
    Microwave plasma-enhanced chemical vapour deposition (MW PE CVD) growth conditions for preparation of polycrystalline phosphorous-doped diamond layers are presented. The incorporation of substitutional phosphorous was confirmed by low temperature photocurrent (PC) and cathodoluminescence (CL) measurements. The topographical characteristics of thefilms and the relation between the substrate and P-dopedfilm grain orientation were studied by scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD). The growth process for P-doped layers on (110) oriented polycrystalline diamond was optimised and the best set of parameters differs significantly from the standard conditions used for P-doping of single crystalline (111) oriented diamond surfaces. (c) 2008 Elsevier...

  13. Super secondary grain growth initiation in electroplated copper

    VANSTREELS, Kris; Brongersma, SH; Demuynck, S; Carbonell, L; D'HAEN, Jan; DE CEUNINCK, Ward; D'OLIESLAEGER, Marc; Maex, K
    Super secondary grain growth is initiated in electroplated copper films deposited on thin seed layers on a alpha-Ta barrier layer. Both growth dynamics and self annealing time strongly depend on the copper seed layer bias conditions, barrier bias conditions, barrier composition and the ECD/PVD thickness ratio. This is consistent with an orientation dependent driving force for super grains in an ECD/PVD bi-layer system. The barrier layer seems to play a critical role in the initiation of abnormal SSGG, while strain energy minimization seems to be an important driving force.

  14. Elucidating the aspect of "phase separation" in organic blends by means of thermal analysis

    SWINNEN, Ann; ZHAO, Xi; Van Assche, G.; VANDERZANDE, Dirk; D'OLIESLAEGER, Marc; MANCA, Jean; Van Mele, B.
    Control of morphology is a key issue in order to improve the performance of organic bulk heterojunction solar cells. Solar cells consisting of a blend of regioregular P3HT (poly(3-hexylthiophene)) and PCBM ([6-6]-phenyl C-61 butyric acid methyl ester) have demonstrated the highest efficiencies until now (up to 5 %). This performance was achieved by applying a post-production annealing, which is considered to induce a dual crystallization behavior. In order to control and tune the morphology, the phase behavior needs to be described in terms of the underlying fundamental thermodynamics. Hence, it is essential to obtain a phase diagram of the blend....

  15. Electrodeposited free-standing single-crystal indium nanowires

    Hautier, Geoffroy; D'HAEN, Jan; Maex, Karen; Vereecken, Philippe M.
    Single-crystal indium nanowires were grown from arrays of holes 150-300 nm in diameter etched into a 300 nm dielectric by potentiostatic electrodeposition from stagnant InCl3-based solutions. The monocrystallinity of the nanowires was confirmed by electron backscattered diffraction measurements. For given experimental conditions, indium wires several micrometers in length grew out of the shallow templates without significant lateral overgrowth, resulting in high-aspect-ratio one-dimensional nanowires. This unusual observation is attributed to a perturbation of the local diffusion field by the neighboring holes or nanowires. (C) 2008 The Electrochemical Society.

  16. A MIP-based impedimetric sensor for the detection of low-MW molecules

    THOELEN, Ronald; VANSWEEVELT, Rob; DUCHATEAU, Jan; HOREMANS, Frederik; D'HAEN, Jan; LUTSEN, Laurence; VANDERZANDE, Dirk; AMELOOT, Marcel; VAN DE VEN, Martin; CLEIJ, Thomas; WAGNER, Patrick
    Mimicking the selectivity and sensitivity of biological systems for sensor devices is of increasing interest in biomedical, environmental and chemical analysis. Synthetic materials with imprinted nanocavities, acting as highly selective artificial receptors, are a tailor-made solution in obtaining such a sensor. Incorporation of such molecularly imprinted polymers (MIPs) in a platform suitable for electrochemical measurements, can offer high sensitivity together with device miniaturization and an electronic read-out. As a proof of principle, a MIP-based sensor for L-nicotine has been developed. To this end, the molecular structure of L-nicotine was imprinted in a polymer matrix of polymethacrylic acid (PMAA). Subsequently, microparticles...

  17. Electrostatic force microscopy studies of boron-doped diamond films

    Gupta, S.; WILLIAMS, Oliver; Bohannan, E.
    Much has been learned from electrochemical properties of boron-doped diamond (BDD) thin films synthesized using microwave plasma-assisted chemical vapor deposition about the factors influencing electrochemical activity, but some characteristics are still not entirely understood, such as its electrical conductivity in relation with microscale structure. Therefore, to effectively utilize these materials, understanding both the microscopic structure and physical (electrical, in particular) properties becomes indispensable. In addition to topography using atomic force microscopy, electrostatic force microscopy (EFM) in phase mode measuring the long-range electrostatic force gradients, helps to map the electrical conductivity heterogeneity of boron-doped micro-/nanocrystalline diamond surfaces. The mapping of electrical...

  18. High-resolution morphological and electrical characterisation of organic bulk heterojunction solar cells by scanning probe microscopy

    DOUHERET, Olivier; SWINNEN, Ann; BERTHO, Sabine; HAELDERMANS, Ilse; D'HAEN, Jan; D'OLIESLAEGER, Marc; VANDERZANDE, Dirk; MANCA, Jean
    State-of-the-art organic bulk heterojunction (BH) solar cells, also called excitonic solar cells, are based on intimate mixtures of donor and acceptor organic materials of which the nanoscale morphology strongly influences both the photovoltaic performances and the stability of the device. In particular, the form and the size of the three-dimensional (3D) interpenetrating network of donor/acceptor material is shown to be crucial for the electrical transport properties and the resulting photovoltaic properties. Powerful high-resolution characterisation tools to locally map the morphology of these material systems are Scanning and Transmission Electron Microscopy (SEM/TEM), Atomic Force Microscopy (AFM) and Nuclear Magnetic Resonance (NMR)....

  19. Aqueous chemical solution deposition of ultrathin lanthanide oxide dielectric films

    HARDY, An; Van Elshocht, Sven; D'HAEN, Jan; DOUHERET, Olivier; De Gendt, Stefan; Adelmann, Christoph; Caymax, Matty; Conard, Thierry; Witters, Thomas; Bender, Hugo; Richard, Olivier; Heyns, Marc; D'OLIESLAEGER, Marc; VAN BAEL, Marlies; MULLENS, Jules
    Ultrathin lanthanide (Nd, Pr, Eu, Sm) oxide films with functional dielectric properties down to 3.3 nm thickness were deposited by aqueous chemical solution deposition (CSD) onto hydrophilic SiO2/Si substrates. Precursor solutions were prepared from the oxides via an intermediate, solid Ln(III)citrate. A film heat treatment scheme was derived from thermogravimetric analysis of the precursor gels, showing complete decomposition by 600 degrees C. Crystalline phase formation in the films depended on the lanthanide, annealing temperature, and citric acid content in the precursor. Through variation of the precursor concentration and number of deposited layers, thickness series of uniform films were obtained down...

  20. Microstructural evolution of cu interconnect under AC, pulsed DC and DC current stress

    BIESEMANS, Leen; VANSTREELS, Kris; BRONGERSMA, Sywert; D'HAEN, Jan; DE CEUNINCK, Ward; D'OLIESLAEGER, Marc
    Damascene Cu interconnects are increasingly used as electrical connections in integrated circuits. During fabrication and operation these interconnects are subjected to temperature variations. These thermal effects cause the different layers of a microelectronic device to undergo mechanical stresses due to differences in thermal coefficients. The same thermal effects can be generated by applying a sinusoidal alternating current (AC) to a sputtered interconnect. Thermal cycling due to joule heating of the interconnect will cause thermal fatigue damage. Our goal is to study this phenomenon on dual damascene Cu interconnects and to compare these results with direct current (DC) and bipolar pulsed...

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