Browsing by Author "Lioudakis, Emmanouil E."
Now showing items 1-20 of 31
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Determination of critical points on silicon nanofilms: Surface and quantum confinement effects
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Nassiopoulou, Androula Galiouna (2008)In this work, we present a comprehensive study of the optical properties of nanocrystalline silicon films with thickness varied from 5 to 30 nm. Spectroscopic ellipsometry is employed to determine the dielectric functions ...
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Direct observation of excitons in polymer/carbon nanotube composites at room temperature: The influence of nanotube concentration
Lioudakis, Emmanouil E.; Kanari, C.; Othonos, Andreas S.; Alexandrou, Ioannis (2008)In this work, we have employed spectroscopic ellipsometry technique to study the optical properties of polymer/carbon nanotube (CN) composites as a function of nanotube concentration. Using a two-layer structural model ...
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Article
Ellipsometric analysis of ion-implanted polycrystalline silicon films before and after annealing
Lioudakis, Emmanouil E.; Nassiopoulou, Androula Galiouna; Othonos, Andreas S. (2006)A study of arsenic ion-implanted polycrystalline silicon films before and after annealing at various temperatures has been performed using spectroscopic ellipsometry in the ultraviolet to the visible spectral region. Using ...
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Ellipsometry on optically thin palladium films on silicon-based substrate: Effects of low concentration of hydrogen
Lioudakis, Emmanouil E.; Othonos, Andreas S. (2005)Optically thin palladium films evaporated on silicon substrates are investigated following exposure to low concentrations of hydrogen gas in nitrogen using spectroscopic ellipsometry. Changes in the parameters tan Ψ and Δ ...
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Article
Femtosecond carrier dynamics in implanted and highly annealed polycrystalline silicon
Lioudakis, Emmanouil E.; Nassiopoulou, Androula Galiouna; Othonos, Andreas S. (2006)We have studied the ultrafast optical response of highly implanted and highly annealed polycrystalline silicon films using 400 nm ultrashort amplified pulses with fluence ranging between 8 mJ cm-2 to 56 mJ cm -2. Transient ...
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Article
Femtosecond carrier dynamics of Inx Ga1-x N thin films grown on GaN (0001): Effect of carrier-defect scattering
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Iliopoulos, Eleftherios; Tsagaraki, K.; Georgakilas, A. (2007)Ultrafast carrier dynamics in ultrathin Inx Ga1-x N ternary alloys were investigated in detail, using femtosecond transient differential optical absorption measurements. Measurements were performed with probing wavelengths ...
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Article
Femtosecond dynamics in single wall carbon nanotube/poly(3-hexylthiophene) composites
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Alexandrou, Ioannis (2008)Femtosecond transient absorption measurements on single wall carbon nanotube/poly(3-hexylthiophene) composites are used to investigate the relaxation dynamics of this blended material. The influence of the addition of ...
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Femtosecond time-resolved study in InxGa1-xN (0001) ultrathin epilayers: Effects of high indium mole fraction and thickness of the films
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Dimakis, Emmanouil; Georgakilas, A. (2006)In view of promising full-solar-spectrum photovoltaic systems based on Inx Ga1-x N ternary alloys, femtosecond time-resolved study in ultrathin epilayers was employed in order to extract the fundamental properties of ...
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Influence of grain size on ultrafast carrier dynamics in thin nanocrystalline silicon films
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Nassiopoulou, Androula Galiouna; Lioutas, Ch B.; Frangis, N. (2007)The ultrafast carrier dynamics in thin nanocrystalline silicon films (10 and 20 nm thick) on quartz over a broad spectral range using optical pumping at a moderate fluence of 2.5 mJ cm2 were studied. The films were composed ...
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Article
Monitoring charge exchange in P3HT-nanotube composites using optical and electrical characterisation
Alexandrou, Ioannis; Lioudakis, Emmanouil E.; Delaportas, Dimitrios; Zhao, C. Z.; Othonos, Andreas S. (2009)Charge exchange at the bulk heterojunctions of composites made by mixing single wall nanotubes (SWNTs) and polymers show potential for use in optoelectronic devices such as solar cells and optical sensors. The density/total ...
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Optical and structural properties of implanted Si wafers: the effects of implantation energy and subsequent isochronal annealing temperature
Lioudakis, Emmanouil E.; Christofides, Constantinos; Othonos, Andreas S. (2006)We have studied the influence of implantation energy and subsequent isochronal annealing temperature on the optical and structural properties of implanted Si wafers employing a multiwavelength spectroscopic ellipsometer. ...
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Article
Optical properties of conjugated poly(3-hexylthiophene)/ [6,6] -phenyl C61 -butyric acid methyl ester composites
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Alexandrou, Ioannis; Hayashi, Y. (2007)In this work, we present the evolution of optical constants as a function of [6,6] -phenyl C61 -butyric acid methyl ester (PCBM) concentration for conjugated poly(3-hexylthiophene)/ [6,6] -phenyl C61 -butyric acid methyl ...
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Optical properties of polyelectrolyte quantum dot multilayer films prepared using the layer by layer self-assembly method
Lioudakis, Emmanouil E.; Koupanou, E.; Kanari, C.; Leontidis, Epameinondas; Othonos, Andreas S. (2008)In this work, we have used spectroscopic ellipsometry to study the optical properties of polyelectrolyte-PbS quantum dot (QD) multilayer films prepared using the layer by layer self-assembly method. The optical results ...
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Conference Object
Optical response of II-VI ZnSe nanowires
Ruda, H. E.; Philipose, U.; Saxena, A.; De Souza, C.; Nair, S.; Salfi, J.; Shik, A.; Othonos, Andreas S.; Lioudakis, Emmanouil E.; Tsokkou, Demetra; Zhong, L.; Fernandes, C. (2010)II-VI nanowires offer a unique combination of properties for developing blue/UV optoelectronic devices. Key to realizing this potential is managing the nanowire growth process to ensure appropriate properties are realized. ...
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Article
Prism-based ultrafast pulse-shaping apparatus
Lioudakis, Emmanouil E.; Adamou, Katerina; Othonos, Andreas S. (2005)We report on a computer-controlled pulse-shaper setup with high-efficiency throughput, based on dispersive prisms, as an alternative to the conventional grating ultrafast pulse-shaping apparatus. A detailed description of ...
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Article
Probing carrier dynamics in implanted and annealed polycrystalline silicon thin films using white light
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Nassiopoulou, Androula Galiouna (2006)Polycrystalline silicon thin film samples implanted and annealed at various temperatures have been studied using ultrafast laser pulse excitation. Nondegenerate pump-probe technique has been utilized to investigate carrier ...
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Article
Quantum confinement and interface structure of Si nanocrystals of sizes 3-5 nm embedded in a-SiO2
Lioudakis, Emmanouil E.; Othonos, Andreas S.; Hadjisavvas, G. C.; Kelires, P. C.; Nassiopoulou, Androula Galiouna (2007)Spectroscopic ellipsometry and Monte Carlo simulations are employed to answer the fundamental question whether the energy gaps of Si nanocrystals with sizes in the range of 3-5 nm, which are embedded in amorphous silica, ...
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Article
The role of surface vibrations and quantum confinement effect to the optical properties of very thin nanocrystalline silicon films
Lioudakis, Emmanouil E.; Antoniou, Antreas; Othonos, Andreas S.; Christofides, Constantinos; Nassiopoulou, Androula Galiouna; Lioutas, Ch B.; Frangis, N. (2007)We report on a spectroscopic study of very thin nanocrystalline silicon films varying between 5 and 30 nm. The role of quantum confinement effect and surface passivation of nanograins in optical properties are examined in ...
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Article
Study of the annealing kinetic effect and implantation energy on phosphorus-implanted silicon wafers using spectroscopic ellipsometry
Lioudakis, Emmanouil E.; Christofides, Constantinos; Othonos, Andreas S. (2006)In this work, we have studied the changes in the optical properties on crystalline silicon implanted wafers (1 × 1013-1 × 1016 P+/cm2) using an extensive ellipsometric analysis. The effects of implantation energy (20-180 ...
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Article
Surface-related states in oxidized silicon nanocrystals enhance carrier relaxation and inhibit auger recombination
Othonos, Andreas S.; Lioudakis, Emmanouil E.; Nassiopoulou, Androula Galiouna (2008)We have studied ultrafast carrier dynamics in oxidized silicon nanocrystals (NCs) and the role that surface-related states play in the various relaxation mechanisms over a broad range of photon excitation energy corresponding ...