Document Server@UHasselt
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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.
Mostrando recursos 1 - 20 de 43
1.
Impedimetric Immunosensors Based on the Conjugated Polymer PPV - Cooreman, Peter; Thoelen, Ronald; Manca, Jean; vande Ven, Martin; Vermeeren, Monique; Michiels, Luc; Ameloot, Marcel; Wagner, Patrick
In the work reported here, we investigated the interaction between the
semiconducting polymer MDMO-PPV and antibodies against the fluorescent dyes
FITC and Cy5. The antibodies are adsorbed physically onto thin polymer films on
gold electrodes, as seen in AFM images of these films. By tuning the antibody
concentration, the contact angle of distilled water with the film can be made to vary
between 95° and 50°, showing that different surface densities of antibody can be
obtained. That these biosensor films specifically bind their antigenic fluorescent
molecules from PBS buffer solution is demonstrated by confocal fluorescence
microscopy. Specific antigen-antibody recognition is demonstrated by lack of crosssensitivity
between the two antibodies...
2.
Mechanism of photoconductivity in intrinsic epitaxial CVD diamond studied by photocurrent spectroscopy and photocurrent decay measurements - Remes, Zdenek; Petersen, Rainer; Haenen, Ken; Nesladek, Milos; D'Olieslaeger, Marc
We report experimental results on photocurrent spectra and the transient decay of photocurrent in intrinsic CVD diamond films grown
homoepitaxially on natural, (100) oriented, single crystal type IIa diamond substrates. The detectors fabricated from these layers were
developed in the frame of the LYRA project (the LYman-alpha RAdiometer onboard the European satellite PROBA-2) and will be used in
space for UV solar monitoring. The typical photosensitivity is about 10(-2) A/W at 200 nm and 10(-6) A/W at 300 nm; the typical response time
well below 0.1 ms. The enhance in photosensitivity, related to defects in CVD diamond layer and accompanied by long, non-exponential tails
in...
3.
Understanding Oxide Degradation Mechanisms in ultra-thin SiO2 through High-Speed, High Resolution in-situ Measurements - Aresu, Stefano; De Ceuninck, Ward; Degraeve, R.; Kaczer, B.; Knuyt, Gilbert; De Schepper, Luc
A model is proposed and validated for the degradation mechanisms occurring in ultra-thin SiO2 at real operation conditions, based on high-resolution, high-speed in-situ measurements. This state-of-the-art set-up proves that oxide degradation still occurs at low stress conditions and allows distinguishing quantitatively the SILC-contribution from the contribution due to trapping.
4.
Head-on immobilization of DNA fragments on CVD-diamond layers - Wenmackers, Sylvia; Christiaens, Pieter; Deferme, Wim; Haenen, Ken; Nesladek, Milos; Wagner, Patrick; Vermeeren, Veronique; Michiels, Luc; vande Ven, Martin; Daenen, Michaël; Ameloot, Marcel; Wouters, J.; Naelaerts, L.; Mekhalif, Z.
Synthetic diamond is regarded as a promising material for biosensors: it forms a stable platform for genetic assays and its biocompatibility opens the possibility for in vivo sensing. In this study the use of a thymidine linker for covalent DNA attachment was evaluated. Contact angle measurements provided a qualitative test of the initially oxidized surface. X-ray photoemission spectroscopy was used for further analysis of the oxides and for monitoring the effect of subsequent chemical treatments. The presence of FITC-labelled DNA was confirmed by confocal fluorescence microscopy. Enzyme linked immunosorbent assays indicated that this DNA was merely adsorbed on the diamond...
5.
Thin nanodiamond membranes and their microstructural, optical and photoelectrical properties - Mortet, Vincent; D'Haen, Jan; Potmesil, J.; Kravets, R.; Drbohlav, I.; Vorlicek, V.; Rosa, J.; Vanecek, M.
We have grown variety of thin nanocrystalline diamond thin layers on silicon substrates with thicknesses ranging from 100 to 2000 nm. Using a bias enhanced nucleation for nucleation density over 1010 cm-2 and changing the deposition conditions and/or using argon dilution we have obtained nanodiamond layers of different structural properties. The nucleation process and growth was monitored with Scanning Electron Microscopy (SEM); cross-section SEM and micro-Raman measurements were used to access the nanodiamond microstructure. Surface topography was followed by SEM and Atomic Force Microscopy. Windows were opened in the silicon substrate to get self-supporting diamond membrane. Diamond membranes are very...
6.
ZnO AlN diamond layered structure for SAW devices combining high velocity and high electromechanical coupling coefficient - El Hakiki, M.; Elmazria, O.; Assouar, M.B.; Mortet, Vincent; Le Brizoual, L.; Vanecek, M.; Alnot, P.
A new layered structure ZnO/AlN/diamond is studied for high frequency and high
electromechanical coupling (K2) SAW devices. Theoretical study was performed to calculate the
phase velocity and K2 dispersion curves of the Rayleigh mode and its higher modes as well as the
leaky waves. Both high values of K2 (>4%) and acoustic velocities higher than 15km/s are
expected with this new structure according to the theoretical results. To confirm the simulation
results, SAW filters were processed on ZnO/AlN/diamond structure. First experimental results are
in accordance with the theoretical ones and confirm the high potentiality of this new structure for
the processing of high performances and high frequencies...
7.
Growth and characterization of near-atomically flat, thick homoepitaxial CVD diamond films - Bogdan, Ganna; Nesladek, Milos; D'Haen, Jan; Maes, J.; Moshchalkov, V.V.; Haenen, Ken; D'Olieslaeger, Marc
Diamond films were grown in an ASTeX MW PE CVD reactor. The effect of pre-growth etching with a
O2/H2 plasma and the influence of the methane concentration on growth on type Ib (100) HPHT synthetic
diamonds were investigated. By controlling step flow growth we were able to prepare optical quality thick
diamond films, free of hillocks and unepitaxial crystallites, with a relatively high growth rate of 4 to
5 µm/h using higher pressures and methane concentrations than standard growth conditions in combination
with a modified substrate holder. All diamond films were characterized by optical microscopy, SEM,
AFM and Raman spectroscopy. The mean roughness (Rms) of the...
8.
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, K.
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...
9.
The characteristics of photon and phonon standing waves in a periodic medium - Knuyt, Gilbert; Nesladek, Milos
The main characteristics of the spatial variation of the photon and phonon wave fields at the band gap boundaries are analysed for a one-dimensional medium with periodic optical or acoustic parameters. The derivations are based on symmetry considerations and on analytical results derived from the basic differential equation for the wave field. A simple relation is derived between the band gap width and the derivative of the field intensity at the interface between the regions of high and low wave velocity. The general field characteristics are derived for some examples. Using the analysis a remarkable asymmetric behaviour of the wave...
10.
DNA attachment to nanocrystalline diamond films - Wenmackers, Sylvia; Christiaens, Pieter; Daenen, Michaël; Haenen, Ken; Nesladek, Milos; vandeVen, Martin; Vermeeren, Veronique; Michiels, Luc; Ameloot, Marcel; Wagner, Patrick
A biochemical method to immobilize DNA on synthetic diamond for biosensor applications is developed.
Nanocrystalline diamond is grown using microwave plasma-enhanced chemical vapour deposition. On the
hydrogen-terminated surface 10-undecenoic acid is tethered photochemically under 254 nm illumination,
followed by 1-ethyl-3-[3-dimethylaminopropyl]carbodiimide crosslinker-mediated attachment of amino
modified DNA. The attachment is functionally confirmed by comparison of supernatant fluorescence and
gel electrophoresis. The linking procedure allowed for 35 denaturation and rehybridisation steps.
11.
The optical absorption and photoconductivity spectra of hexagonal boron nitride single crystals - Remes, Zdenek; Nesladek, Milos; Haenen, Ken; Watanabe, K.; Taniguchi, T.
Recently, a strong cathodoluminescence at 215 nm (photon energy 5.765 eV) has been reported on pure
HPHT hexagonal boron nitride (hBN) single crystals (K. Watanabe et al., Nature Mater. 3, 404 (2004)).
For the first time, we measured the photocurrent and optical absorption spectra of these new hBN crystals
in a broad spectral range 16.6 eV. Our measurements support the previously published results, especially
that the single crystal hBN has a direct band gap about 5.95 eV, and a rather strong exciton binding
energy that allows excitons to exist even at room temperature. We found three new opto-electronic transitions
at 2.7, 3.6 and 5.4 eV and...
12.
PTIS investigation of hydrogenated CVD diamond films - Hikavyy, A.; Clauws, P.; Deferme, Wim; Bogdan, Ganna; Haenen, Ken; Nesladek, Milos
Photo-thermal ionization spectroscopy has been applied for investigation of hydrogenated diamond. All
investigated films have shown presence of B after hydrogenation though no PTIS could be measured
when they were oxidized. The presence of shallow levels with energy around 100 meV has been found in
all hydrogenated samples at temperatures lower than 12077 K depending on the sample. The photocurrent
spectrum due to these shallow levels consists of features similar to two-phonon absorption in diamond.
13.
Thin Films of highly luminescent lanthanide complexes covalently linked to an organic-inorganic hybrid material via 2-substituted imidazo[4,5-f]-1,10-phenanthroline groups - Lenaerts, Philip; Storms, Annick; Mullens, Jules; D'Haen, Jan; Görller-Walrand, Christiane; Binnemans, Koen; Driesen, Kris
A homogeneous distribution of luminescent lanthanide(III) 2-thenoyltrifluoroacetonate complexes
(Ln ) Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm, Yb) in an organic-inorganic hybrid material was obtained by
grafting the complexes to the solid matrix via 2-substituted imidazo[4,5-f]-1,10-phenanthroline moieties.
Thin films of the silica hybrid material were prepared by the sol-gel method and by spin-coating of the
gelating solution on glass slides or on oxidized silicon wafers. The thickness of the thin films was
determined by scanning electron microscopy (SEM). High-resolution luminescence spectra of the lanthanide
complexes were recorded, and the luminescence decay times were measured. The luminescence quantum
yields of europium(III)-doped thin films exposed to different drying...
14.
Absorption phenomena in organic thin films for solar cell applications investigated by photothermal defelction spectroscopy - Goris, Ludwig; Haenen, Ken; Nesladek, Milos; Wagner, Patrick; Vanderzande, Dirk; De Schepper, Luc; D'Haen, Jan; Lutsen, Laurence; Manca, Jean
A high sensitive approach is presented to detect in particular the low level absorption
features in pure and blended organic semiconductor films, revealing a.o. defect induced
sub gap absorption and new interactions between the materials. Because sub bandgap
absorption features are typically characterized by very low absorption coefficients, it is not
possible to resolve them using common transmission and reflection measurements.
Therefore the very sensitive and ground state spectroscopic technique of Photothermal
Deflection Spectroscopy (PDS) has been developed, and introduced to characterize thin
films of MDMO-PPV and PCBM, as well as films of MDMO-PPV containing an increasing
amount of PCBM ranging from 5 to 90% weight fraction. The...
15.
LYRA: The solar UV radiometer aboard the ESA Proba-2 - Hochedez, J.-F.; Schmutz, W.; Nesladek, Milos; Stockman, Y.; Schühle, U.; BenMoussa, A.; Koller, S.; Haenen, Ken; Berghmans, D.; Defise, J.-M.; Halain, J.-P.; Theissen, A.; Delouille, V.; Slemzin, V.; Gillotay, D.; Fussen, D.; Dominique, M.; Vanhellemont, F.; McMullin, D.; Kretzschmar, M.; Mitrofanov, A.; Nicula, B.; Wauters, L.; Roth, H.; Rozanov, E.; Ruëdi, I.; Wehrli, C.; Amano, A.; Van der Linden, R.; Zhukov, A.; Clette, F.; Koizumi, S.; Mortet, Vincent; Remes, Zdenek; Petersen, Rainer; D'Olieslaeger, Marc; Roggen, Jean; Rochus, P.
LYRA is the solar UV radiometer that will embark in 2006 aboard Proba{2, a tech-
nologically oriented ESA micro-mission. LYRA is designed and manufactured by a
Belgian{Swiss{German consortium (ROB, PMOD/WRC, IMOMEC, CSL, MPS &
BISA) with additional international collaborations. It will monitor the solar irra-
diance in 4 UV passbands. The channels have been chosen for their relevance to
Solar Physics, Aeronomy, and Space Weather: 1/ 115-125 nm (Lyman{®), 2/ the
200{220 nm Herzberg continuum range, 3/ Aluminium ¯lter channel (17{30 nm)
including He II at 30.4 nm, and 4/ Zirconium ¯lter channel (1{20 nm). The ra-
diometric calibration will be traceable to synchrotron source standards (PTB &
NIST),...
16.
Solar-blind diamond detectors for Lyra, the solar VUV radiometer on board Proba II - Benmoussa, A.; Hochedez, J.-F.; Schmutz, W.K.; Schühle, U.; Nesladek, Milos; Stockman, Y.; Kroth, U.; Richter, M.; Theissen, A.; Remes, Zdenek; Haenen, Ken; Mortet, Vincent; Koller, S.; Halain, J.P.; Petersen, Rainer; Dominique, M.; D'Olieslaeger, Marc
Fabrication, packaging and experimental esults on the calibration of metal-semiconductormetal
(MSM) photodetectors made on diamond are reported. LYRA (Lyman-? RAdiometer onboard
PROBA-2) will use diamond detectors for the first time in space for a solar physics instrument. A set of measurement campaigns was designed to obtain the XUV-to-VIS responsivity of the devices and other characterizations. The measurements of responsivity in EUV and VUV spectral ranges (40240 nm) have been carried out by the Physkalisch-Technische Bundesanstalt (PTB) in Germany at the electron storage ring BESSY II. The longer wavelength range from 210 to 1127 nm was measured with monochromatic light by using a...
17.
Conventional n-type doping in diamond: state of the art and recent progress - Nesladek, Milos
Recent progress in chemical vapour deposition (CVD) diamond technology has enabled the preparation of high-quality n-type CVD diamond layers using phosphorus as a dopant. CVD diamond can therefore be considered as a new interesting conventional wide-gap semiconducting material having both n- and p-type dopants, which makes it attractive for numerous applications in high-temperature, high-voltage and high-frequency devices. The concentration of phosphorus in n-type CVD diamond can be controlled in the concentration range of 1 × 10165 × 1019 cm-3 with a carrier mobility exceeding 600 cm2 V-1 s-1. In this review, the most relevant questions concerning the preparation of P-doped...
18.
Failure mechanisms and qualification testing of passive components - Post, H.A.; Letullier, P.; Briolat, T.; Humke, R.; Schuhmann, R.; Saarinen, K.; Werner, W.; Ousten, Y.; Lekens, Geert; Dehbi, A.; Wondrak, W.
New electronic architectures and mechatronic integration in automotive and oil-field applications lead to
increasing requirements concerning operating temperatures and vibration levels. At the same time, reliability and
lifetime have to fulfil strong demands.
In the European funded project PROCURE (Program for the development of passive devices used in rough
environments) a generic spectrum of passive components needed for electronic control units has been developed. The
failure mechanisms, the technological challenges, and the test requirements are highlighted below.
19.
Effect of pyrolysis temperature on the properties of Bi3.5 La0.5O12 thin films deposited by aquous chemical solution deposition - Hardy, An; Nelis, Daniël; Vanhoyland, Geert; Van Bael, Marlies; Van den Rul, Heidi; Mullens, Jules; Van Poucke, Lucien; D'Haen, Jan; Goux, L.; Wouters, D.J.
Bi3.5La0.5Ti3O12 thin films for ferroelectric random access memory application were fabricated by the aqueous chemical solution deposition method. The precursor films were deposited by spin coating and subsequently transformed into the oxide by thermal treatment on three hot plates and crystallizing in a rapid thermal processing furnace at a temperature as low as 650 °C. The temperature of the third hot plate step was varied, which affected the ferroelectric properties of the prepared films. The ferroelectric properties of the crystallized films as well as their crystallographic structure, texture and microstructure were characterized using various experimental techniques. The evolution of the...
20.
Cadmium tolerance in Thlaspi caerulescens II. Localization of cadmium in Thlaspi caerulescens - Wojcik, M.; Vangronsveld, Jaco; D'Haen, Jan; Tukiendorf, A.
Tissue and cellular compartmentation of Cd in roots and leaves of the hyperaccumulator Thlaspi caerulescens was investigated, using energy-dispersive X-ray microanalysis. In roots, Cd was determined in cortex parenchyma cells, endodermis, parenchyma cells of the central cylinder and xylem vessels. In leaves, it was found in cells lying on the way of water migration from the vascular cylinder to epidermal cells, which is in line with passive Cd transport by the transpiration stream. The mechanisms of Cd-detoxification in roots seem to be localized both in apoplast (e.g. binding to cell wall compounds) and inside cells since Cd was accumulated in...
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