Agia Paraskevi, Greece
Agia Paraskevi, Greece

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Papanikolaou N.,Institute of Microelectronics, Greece | Psarobas I.E.,Institute of Microelectronics, Greece | Stefanou N.,National and Kapodistrian University of Athens
Applied Physics Letters | Year: 2010

By means of full electrodynamic and elastodynamic multiple-scattering calculations we study the optical and acoustic properties of three-dimensional lattices of metallic nanospheres implanted in a dielectric host. Our results show that such structures exhibit omnidirectional spectral gaps for both telecom infrared light and hypersound, with relatively low absorptive losses. This class of dual (phoxonic) band-gap materials is an essential step toward the hypersonic modulation of light and could lead to the development of efficient acousto-optical devices. © 2010 American Institute of Physics.

Kokkinos C.,National and Kapodistrian University of Athens | Economou A.,National and Kapodistrian University of Athens | Raptis I.,Institute of Microelectronics, Greece
Analytica Chimica Acta | Year: 2012

This work reports the fabrication of disposable three-electrode cells with integrated metal-film electrodes. The devices were fabricated by a multi-step micro-fabrication approach combining sputtering for the deposition of metals and the dielectric material (SiO 2) on the surface of a silicon wafer and photolithography for the definition of the geometry of the sensors. The working electrode was a microelectrode array consisting of bismuth microdisks while the reference and counter electrode strips were made of Ag and Pt, respectively. The utility of these devices was tested for the trace determination of Pb(II) and Cd(II) by anodic stripping voltammetry and Ni(II) by adsorptive stripping voltammetry. The detection of these trace metals was carried out in unstirred and undeoxygenated solutions exhibiting sub-μgL -1 limits of detection and enhanced analytical characteristics compared to conventional bismuth-film electrodes. © 2011 Elsevier B.V.

Polychronopoulou K.,University of Cyprus | Giannakopoulos K.,Institute of Materials Science | Giannakopoulos K.,Institute of Microelectronics, Greece | Efstathiou A.M.,University of Cyprus
Applied Catalysis B: Environmental | Year: 2012

The present work is focused on the sol-gel synthesis, characterization and catalytic performance evaluation of novel Mg-Ce-Zr-O-based mixed oxides supported Rh catalysts for the purification of H 2-rich gas streams from phenol through steam reforming in the 575-730°C range. Phenol is used as a model compound of tars, the former being one of the main constituents of tars formed during steam gasification and pyrolysis of biomass. Novel Rh catalysts (0.1wt%) supported on Mg-Ce-Zr-O-based mixed oxides modified by alkaline-earth, rare earth, and transition metal ions, having the general formula Mg-Ce-Zr-X-O (where X stands for La, Sr, Ba, Ca and Zn) were systematically studied. The physicochemical properties of the catalysts were evaluated using complementary bulk and surface characterization techniques, such as BET, XPS, in situ XRD, TEM/SAED and SEM/EDX. Transient techniques including H 2-TPR, TPD-CO 2 and TPD-NH 3 were employed in order to characterize redox behavior, surface basicity, and surface acidity of support, respectively. Among the catalysts examined, a 0.1wt% Rh/40Mg-20Ce-20Zr-20La-O was found to exhibit the highest hydrogen product yield, specific H 2 production rate (μmol/m 2min), and the lowest CO/CO 2 product ratio (575-730°C), even when compared to a Ni-based commercial steam reforming of tars catalyst. At 655°C, a H 2 yield of ∼95% and a specific reaction rate of 100μmolH 2/m 2min were obtained for a feed containing 0.5vol% phenol and 40vol% H 2O at a gas hourly space velocity of ∼80,000h -1. This activity behavior is correlated with the largest concentration of basic sites and labile oxygen species (μmol/m 2), and also with the largest acid/base site ratio present in the 40Mg-20Ce-20Zr-20La-O support composition. Steam was also found to be an efficient reagent for the removal of carbonaceous deposits (e.g., C xH y) formed on the catalyst surface during phenol steam reforming. The H/C atom compositional ratio of the carbonaceous deposits was found to depend on reaction temperature. © 2011 Elsevier B.V.

Pasparakis G.,Foundation for Research and Technology Hellas | Manouras T.,Institute of Microelectronics, Greece | Argitis P.,Institute of Microelectronics, Greece | Vamvakaki M.,Foundation for Research and Technology Hellas | Vamvakaki M.,University of Crete
Macromolecular Rapid Communications | Year: 2012

Photodegradable polymers constitute an emerging class of materials that finds numerous applications in biotechnology, biomedicine, and nanoscience. This article highlights some of the emerging applications of photodegradable polymers in the form of homopolymers, particles and self-assembled constructs in solution, hydrogels for tissue engineering, and photolabile polymers for biopatterning applications. Novel photochemistries have been combined with controlled polymerization methods, which result in well-defined photodegradable materials that exhibit light mediated and often controlled fragmentation processes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vourdas N.,Technological Educational Institute of Sterea Ellada | Tserepi A.,Institute of Microelectronics, Greece | Stathopoulos V.N.,Technological Educational Institute of Sterea Ellada
Applied Physics Letters | Year: 2013

We present a generic method to reversibly switch the mobility of a droplet after impingement onto a hydrophobic porous surface, from a sticky to a slippery state and back. By means of a pneumatic system, the backpressure of the porous medium is adjusted to favor the pressure balance towards the desired state. By applying overpressure above a certain threshold, the antiwetting pressures increase over the wetting pressures, which eventually results to a slippery state, while vacuum enhances the wetting pressures, thus, rendering the droplet sticky. This pressure-induced switching method is very flexible and can be applied even after decay of the hydrophobic character of the porous medium, does not entail the use of a superhydrophobic or hierarchical surface, and can be applied for actuation and valving in microfluidics. © 2013 AIP Publishing LLC.

Ellinas K.,Institute of Microelectronics, Greece | Tserepi A.,Institute of Microelectronics, Greece | Gogolides E.,Institute of Microelectronics, Greece
Langmuir | Year: 2011

Ordered, hierarchical (triple-scale), superhydrophobic, oleophobic, superoleophobic, and amphiphilic surfaces on poly(methyl methacrylate) PMMA polymer substrates are fabricated using polystyrene (PS) microparticle colloidal lithography, followed by oxygen plasma etching-nanotexturing (for amphiphilic surfaces) and optional subsequent fluorocarbon plasma deposition (for amphiphobic surfaces). The PS colloidal microparticles were assembled by spin-coating. After etching/nanotexturing, the PMMA plates are amphiphilic and exhibit hierarchical (triple-scale) roughness with microscale ordered columns, and dual-scale (hundred nano/ten nano meter) nanoscale texture on the particles (top of the column) and on the etched PMMA surface. The spacing, diameter, height, and reentrant profile of the microcolumns are controlled with the etching process. Following the design requirements for superamphiphobic surfaces, we demonstrate enhancement of both hydrophobicity and oleophobicity as a result of hierarchical (triple-scale) and re-entrant topography. After fluorocarbon film deposition, we demonstrate superhydrophobic surfaces (contact angle for water 168°, compared to 110° for a flat surface), as well as superoleophobic surfaces (153° for diiodomethane, compared to 80° for a flat surface). © 2011 American Chemical Society.

Vasilopoulou M.,Institute of Microelectronics, Greece | Davazoglou D.,Institute of Microelectronics, Greece
Materials Science in Semiconductor Processing | Year: 2013

The purpose of this work is to give an account of the benefits gained by the use of hot-wire vapor deposited tungsten and molybdenum oxide thin films for carrier injection/transport in organic optoelectronic devices. The manuscript is divided in five parts: after a general introduction in organic (opto-) electronic devices, a brief theoretical introduction is done in the physics of transition metal oxides, with emphasis to tungsten and molybdenum, of organic semiconductors and of the semiconductor/metal contacts. Then the experimental method of hot-wire vapor deposition of tungsten and molybdenum oxide is described. Results, dealing mainly with the electronic structure and the microstructure of hot-wire tungsten and molybdenum oxide films are reported next. In particular, it is reported how the stoichiometry and the doping of these oxides with hydrogen alters their electronic structure. Then the benefits gained by using these hot-wire deposited oxide films for injecting/transport of carriers in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs) are reported and discussed in conjunction with the electronic structure of oxide films. Finally, it is concluded that the hot-wire vapor deposition of W and Mo oxide films is a simple, versatile and inexpensive technique allowing for the precise compositional control of the deposited layers, therefore their electronic structure. The use of such layers to modify the interfaces organic semiconductor/electrodes of OLEDs and OSCs causes significant improvements of the performance of these devices and improves spectacularly their stability in ambient air. © 2013 Elsevier Ltd.

Tsougeni K.,Institute of Microelectronics, Greece | Papageorgiou D.,Institute of Microelectronics, Greece | Tserepi A.,Institute of Microelectronics, Greece | Gogolides E.,Institute of Microelectronics, Greece
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2010

We demonstrate a mass-production-amenable technology for fabrication, surface modification and multifunction integration in polymeric microfluidic devices, namely direct lithography on the polymeric substrate followed by polymer plasma etching, and selective plasma deposition. We apply the plasma processing technology to fabricate polymeric microfluidics in poly(methyl methacrylate) (PMMA) and poly(ether ether ketone) (PEEK). First, deep anisotropic O 2 plasma etching is utilized to pattern the polymer via an in situ, highly etch-resistant, thin, Si-containing photoresist, or via a thick organic photoresist. Absolute control of surface roughness (from smooth to very rough), and the production of stable-in-time (slowly ageing) superhydrophilic microchannels are demonstrated. Second, we demonstrate the spontaneous capillary pumping through such rough, superhydrophilic plasma-etched microchannels in contrast to smooth ones, even 5 weeks after fabrication. Third, by using C 4F 8 fluorocarbon plasma deposition through a stencil mask, we produce superhydrophobic patches inside the microchannels, and use them as passive valves. Our approach proposes "smart" multifunctional microfluidics fabricated by a plasma technology toolbox. © 2010 The Royal Society of Chemistry.

Hourdakis E.,Institute of Microelectronics, Greece | Nassiopoulou A.G.,Institute of Microelectronics, Greece
Microelectronic Engineering | Year: 2012

We report on the fabrication and electrical characterization of MIM capacitors using barrier type anodic alumina dielectric between Al electrodes. Its fabrication is based on CMOS compatible room temperature processing using electrochemistry which is a simple and cost effective process. The obtained capacitors exhibit large capacitance density (above 7 fF/μm2) and very small leakage current for a voltage range between -2 V and 2 V (below the background noise of our measurement system). The electrical characteristics of the capacitor are directly compared to those attained previously by the authors using porous anodic alumina instead of the barrier type one. It is shown that there is a significant improvement in both the value of the capacitance density and the value of the non-linearity coefficient α. © 2011 Elsevier B.V. All rights reserved.

Hourdakis E.,Institute of Microelectronics, Greece | Nassiopoulou A.G.,Institute of Microelectronics, Greece
IEEE Transactions on Electron Devices | Year: 2010

We report on the fabrication and electrical characterization of MIM capacitors using as dielectric a thin porous anodic alumina layer between two Al films. The Al2O3/Al stack is grown electrochemically by partly anodizing an Al film on Si, while a top Al film is then deposited on the aluminum oxide and patterned in order to define the capacitor area. The obtained MIM capacitors exhibit at the same time large capacitance density (above ∼5 fF/μm2), low leakage current density (below ∼10-9 A/cm2 at 2 V), and good thermal stability of operation, demonstrated by an α coefficient that changes by less than 10% for temperature changes of the order of 100 K. The temperature stability is further demonstrated by the low leakage current density (below ∼7 × 10-9 A/cm 2) even at temperatures as high as 420 K. © 2006 IEEE.

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