References of "Nguyen, Ngoc Duy"
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See detailMagnetic flux penetration in Nb superconducting films with lithographically defined micro-indentations
Brisbois, Jérémy ULg; Adami, Obaïd-Allah ULg; Avila Osses, Jonathan ULg et al

in Physical Review B (2016)

We present a thorough investigation by magneto-optical imaging of the magnetic flux penetration in Nb thin films with lithographically defined border indentations. We demonstrate that discontinuity lines ... [more ▼]

We present a thorough investigation by magneto-optical imaging of the magnetic flux penetration in Nb thin films with lithographically defined border indentations. We demonstrate that discontinuity lines (d-lines), caused by the abrupt bending of current streamlines around the indentations, depart from the expected parabolic trend close to the defect and depend on the shape and size of the indentation as well as on the temperature. These findings are backed up and compared with theoretical results obtained by numerical simulations and analytical calculations highlighting the key role played by demagnetization effects and the creep exponent n. In addition, we show that the presence of nearby indentations and submicrometer random roughness of the sample border can severely modify the flux front topology and dynamics. Strikingly, in contrast to what has been repeatedly predicted in the literature, we do not observe that indentations act as nucleation spots for flux avalanches, but they instead help to release the flux pressure and avoid thermomagnetic instabilities. [less ▲]

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See detailAnalysis of the time-dependent electrical current in reverse-biased p-GeSn/n-Ge mesa diodes
Baert, Bruno ULg; Gupta, Somya; Gencarelli, Federica et al

Poster (2015, September)

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See detailMagnesium-doped Cuprous Oxide (Mg:Cu2O) thin films as a transparent p-type semiconductor oxide
Avelas Resende, João ULg; Nguyen, Ngoc Duy ULg; Deschanvres, Jean-Luc et al

Poster (2015, September)

Oxide electronics is an important emerging area, notably for the development of transparent thin film transistors (TFTs) and other complex electronic circuits. The successful application of n-type oxides ... [more ▼]

Oxide electronics is an important emerging area, notably for the development of transparent thin film transistors (TFTs) and other complex electronic circuits. The successful application of n-type oxides to TFTs has motivated the interest in p-type oxide based semiconductors, also to be applied to TFTs or to complementary metal-oxide semiconductor (CMOS) technology. However, until now there is a lack of p-type oxide semiconductors with performance similar to that of n-type oxide. Among the different metallic oxides, Cu (I)-based oxides exhibit one of the lowest ionic character. These compounds are therefore one of the most promising candidates as p-type transparent semiconductors.Nevertheless, the band gap of 2,17eV is modest for transparent electronics applications, since the transmittance of Cu2O films is low on the visible part of the light spectrum. The incorporation of cations with large radii than Cu has been proposed as a way to achieve a higher band gap, by diminishing of three-dimensional Cu-Cu interactions, only possible with larger cations than Cu+. Therefore, cation doped Cu2O thin films were grown by metal-organic chemical vapor deposition (MOCVD). The three doping elements studied (Sr2+, Sn2+ and La3+) were selected having in account theoretical predictions for the band structure and the deposition conditions of Cu2O. The study focus on thin films growth optimization combined with electronic transport analysis and optical transmittance measurements. [less ▲]

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See detailElectrical characterization of p-GeSn/n-Ge diodes with interface traps under dc and ac regimes
Baert, Bruno ULg; Gupta, Somya; Gencarelli, Federica et al

in Solid-State Electronics (2015), 110

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See detailReverse current transient behavior of pGeSn/nGe diodes
Baert, Bruno ULg; Gupta, Somya; Gencarelli, Federica et al

Conference (2015)

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See detailCombining mesoporosity and Ti-doping in hematite films for water splitting
Toussaint, Caroline ULg; Tran, Hoang Son ULg; Colson, Pierre ULg et al

in Journal of Physical Chemistry C (2015), 119(4), 1642-1650

(Graph Presented). In this study, we report the synthesis of Ti-doped mesoporous hematite films by soft-templating for application as photoanodes in the photoelectrolysis of water (water splitting ... [more ▼]

(Graph Presented). In this study, we report the synthesis of Ti-doped mesoporous hematite films by soft-templating for application as photoanodes in the photoelectrolysis of water (water splitting). Because the activation of the dopant requires a heat treatment at high temperature (≥800°C), it usually results in the collapse of the mesostructure. We have overcome this obstacle by using a temporary SiO2 scaffold to hinder crystallite growth and thereby maintain the mesoporosity. The beneficial effect of the activated dopant has been confirmed by comparing the photocurrent of doped and undoped films treated at different temperatures. The role of the mesostructure was investigated by comparing dense, collapsed, and mesoporous films heated at different temperatures and characterized under front and back illumination. It turns out that the preservation of the mesotructure enables a better penetration of the electrolyte into the film and therefore reduces the distance that the photogenerated holes have to travel to reach the electrolyte. As a result, we found that mesoporous films with dopant activation at 850°C perform better than comparable dense and collapsed films. [less ▲]

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See detailElectrical modelling of interface traps in GeSn MOS structures
Baert, Bruno ULg; Cerica, Delphine ULg; Schmeits, Marcel ULg et al

Conference (2014, November 13)

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See detailClassical analogy for the deflection of flux avalanches by a metallic layer
Brisbois, Jérémy ULg; Vanderheyden, Benoît ULg; Colauto, Fabiano et al

in New Journal of Physics (2014), 16(10), 103003

Sudden avalanches of magnetic flux bursting into a superconducting sample undergo deflections of their trajectories when encountering a conductive layer deposited on top of the superconductor. Remarkably ... [more ▼]

Sudden avalanches of magnetic flux bursting into a superconducting sample undergo deflections of their trajectories when encountering a conductive layer deposited on top of the superconductor. Remarkably, in some cases the flux is totally excluded from the area covered by the conductive layer. We present a simple classical model that accounts for this behaviour and considers a magnetic monopole approaching a semi-infinite conductive plane. This model suggests that magnetic braking is an important mechanism responsible for avalanche deflection. [less ▲]

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See detailImpact of traps on the electrical characteristics of GeSn/Ge diodes
Baert, Bruno ULg; Gupta, Somya; Gencarelli, Federica et al

Poster (2014, September 15)

Germanium-tin alloys are currently receiving a lot of attention as materials for high performance MOSFET devices. Much interest is focused on the direct band gap for Sn concentrations above 8-10% and the ... [more ▼]

Germanium-tin alloys are currently receiving a lot of attention as materials for high performance MOSFET devices. Much interest is focused on the direct band gap for Sn concentrations above 8-10% and the achievement of high mobility values, which can be further increased by the strain due to the lattice mismatch with Ge or Si. GeSn is therefore expected to play a key role in the development of either source and drain stressors for Ge p-MOSFETs or for GeSn channel MOSFETs. However, despite recent tremendous progress in the growth of such materials, the impact of defects at the interface between Ge and GeSn has not been completely characterized. As the processing of diodes contains many of the steps necessary to the fabrication of MOSFET devices, we have investigated the effect of traps on the electrical characteristics of p-GeSn/n-Ge diodes, made from GeSn layers grown by CVD on Ge and in-situ doped with Boron. Using temperature-dependent current-voltage (I-V) and capacitance- voltage (C-V) measurements, we have calculated the ideality factor of the diodes, the activation energy of the reverse saturation current and the carrier concentration of the Ge substrate. In this work, based on the comparison with results obtained from numerical simulations, we discuss these characteristics in view of assessing the extent to which electronic trap states in these heterostructures affect their electrical properties. [less ▲]

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See detailElectrical characterization of pGeSn/nGe diodes
Baert, Bruno ULg; Gupta, Somya; Gencarelli, Federica et al

Conference (2014, June 03)

I-V characteristics of pGeSn/nGe diodes have been measured and show very good properties. Simulations of the same structure are able to reproduce most of the observed behavior and point to the ... [more ▼]

I-V characteristics of pGeSn/nGe diodes have been measured and show very good properties. Simulations of the same structure are able to reproduce most of the observed behavior and point to the predominating influence of parameters such as the band gap energy of the GeSn layer. C-V characteristics showing little frequency dependence have also been measured, and their analysis for the determination of the carrier concentration is confirmed by simulations. More investigations, including the effect of temperature and other defects at the interface or in the bulk of either layers are still required in order to explain some of the observed behaviors, notably the reverse saturation current. [less ▲]

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See detailMetallic nanowire networks: effects of thermal annealing on electrical resistance
Langley, Daniel ULg; Lagrange, Mélanie; Giusti, Gael et al

in Nanoscale (2014), 6

Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing ... [more ▼]

Metallic nanowire networks have huge potential in devices requiring transparent electrodes. This article describes how the electrical resistance of metal nanowire networks evolve under thermal annealing. Understanding the behavior of such films is crucial for the optimization of transparent electrodes which find many applications. An in-depth investigation of silver nanowire networks under different annealing conditions provides a case study demonstrating that several mechanisms, namely local sintering and desorption of organic residues, are responsible for the reduction of the systems electrical resistance. Optimization of the annealing led to specimens with transmittance of 90% (at 550 nm) and sheet resistance of 9.5 Ω sq−1. Quantized steps in resistance were observed and a model is proposed which provides good agreement with the experimental results. In terms of thermal behavior, we demonstrate that there is a maximum thermal budget that these electrodes can tolerate due to spheroidization of the nanowires. This budget is determined by two main factors: the thermal loading and the wire diameter. This result enables the fabrication and optimization of transparent metal nanowire electrodes for solar cells, organic electronics and flexible displays. [less ▲]

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See detailTransparent electrodes composed of silver nanowire networks: physical properties and potential applications
Langley, Daniel ULg; Lagrange, Mélanie; Munoz-Rojas, David et al

Conference (2014)

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See detailTransparent electrodes composed of silver nanowire networks for photovoltaic applications
Langley, Daniel ULg; Lagrange, Mélanie; Munoz-Rojas, David et al

Conference (2014)

Research is increasingly being dedicated towards replacing rare earth elements in Transparent Conductive Materials (TCMs). In this work we present the investigation of silver nanowire (AgNW) networks as ... [more ▼]

Research is increasingly being dedicated towards replacing rare earth elements in Transparent Conductive Materials (TCMs). In this work we present the investigation of silver nanowire (AgNW) networks as transparent electrodes for solar cell applications. Metallic nanowire networks can be deposited via low cost deposition techniques and exhibit very interesting electrical, optical and mechanical properties. Experimental and simulation approaches aim at improving their physical properties. Indeed, we show that a thermal annealing can drastically improve transport properties of the nearly transparent networks. We also explore the optimization of the network density. These percolating networks exhibit excellent properties (i.e. sheet resistances (Rs) of about 10 Ω/sq and optical transparency of approximately 90%) compatible with solar applications requirements. This makes them very appropriate for future uses in low cost, large area and flexible solar and display technologies. A comprehensive understanding of the main physical properties of this promising nanostructured network and its integration with solar cells will then be presented [less ▲]

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See detailInnovative Electrodes for Dye Sensitized Solar Cells
Langley, Daniel ULg; Giusti, Gael; Zhang, Shanting et al

Conference (2014)

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See detailInterplay between defects in metallic nanowire networks and their physical properties: a modeling and experimental approach
Lagrange, Mélanie; Langley, Daniel ULg; Munos-Rojas et al

Conference (2014)

The use of random metallic nanowire networks as transparent conductive materials (TCMs) is increasing rapidly. These materials can be used in flexible/stretchable electronics, flexible displays, touch ... [more ▼]

The use of random metallic nanowire networks as transparent conductive materials (TCMs) is increasing rapidly. These materials can be used in flexible/stretchable electronics, flexible displays, touch screens, photovoltaics or as transparent heaters. Metallic nanowire networks can be deposited by using low-cost and scalable deposition techniques and exhibit very interesting electrical, optical, thermal and mechanical properties. In addition to usual material defects (such as grain-boundaries) any deviation from a “perfect” infinite network (i.e. nanowire length distributions, finite device size or nanowire curvature for instance) play a prominent role in the physical properties of the resulting percolating network. Using Monte Carlo simulations, and based on experimental available wires the effects of these defects are explored. Experimental work is focused on the influence of nanowire density as well as defects within the nanostructured network such as the inhomogeneity of the network, the grain-boundary along a nanowire, the morphological nanowire instabilities… The influence of these defects on the physical properties of this promising nanostructured network will be presented [less ▲]

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See detailMetallic nanowire networks for energy applications: experimental and modelling approaches
Langley, Daniel ULg; Lagrange, Mélanie; Munoz-Rojas, David et al

Conference (2014)

Research is increasingly being dedicated towards finding emerging materials aiming at playing a prominent role in energy issues. Transparent electrodes are a key component of devices such as solar cells ... [more ▼]

Research is increasingly being dedicated towards finding emerging materials aiming at playing a prominent role in energy issues. Transparent electrodes are a key component of devices such as solar cells or efficient lighting (such as OLED). Among emerging transparent conductive materials, metallic nanowire networks appear to be a very promising solution. This work aims at designing and optimizing metallic nanowire networks based on both experimental and modelling approaches. The influence on the networks physical properties of several key parameters such as the metal/alloy used, thermal annealing, network density, device size, etc. are explored. These percolating networks exhibit excellent properties (sheet resistances and optical transparency of about 10 Ω/ sq and 90%, respectively) fulfilling the requirements for solar or efficient opto-electronic applications. This makes them very appropriate for future uses involving large area and flexible photovoltaics or efficient lighting display technologies. A comprehensive understanding of the design and main physical properties of these promising nanostructured networks will be presented [less ▲]

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See detailThermal properties of silver nanowire networks
Sorel, Sophie; Lagrange, Mélanie; Langley, Daniel ULg et al

Conference (2014)

Silver nanowire (AgNW) networks have recently been the focus of intense research due to their potential use as transparent electrodes in solar cells, flat panel displays or transparent heaters. Metallic ... [more ▼]

Silver nanowire (AgNW) networks have recently been the focus of intense research due to their potential use as transparent electrodes in solar cells, flat panel displays or transparent heaters. Metallic nanowire networks can be deposited using low-cost and scalable deposition techniques on flexible substrates. For improving the transport properties (thermal and electrical) and optical transmittance in the visible range, an optimum nanowire density should be considered. In the present contribution we investigate the thermal behaviour of AgNW networks based on two aspects. The first one shows that a thermal annealing can drastically improve transport properties. The second approach investigates the physical properties of the network when used to generate heat. Experimental observation shows that AgNW networks exhibit the properties of a very efficient transparent heater, making them appropriate for future uses compatible with large area and flexible display technology. A comprehensive understanding of the thermal properties of this promising transparent nanostructured network will be presented. [less ▲]

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See detailHighly Diffuse Fluorine-doped SnO2 Thin Films for Photovoltaic Applications
Giusti, Gael; Consonni, Vincent; Langley, Daniel ULg et al

Conference (2014)

In the last decades, polycrystalline fluorine-doped SnO2 (FTO) thin films have received increasing interest due to their promising application in a wide variety of devices such as gas sensors, coatings ... [more ▼]

In the last decades, polycrystalline fluorine-doped SnO2 (FTO) thin films have received increasing interest due to their promising application in a wide variety of devices such as gas sensors, coatings and electrodes for solar cells. FTO thin films exhibit good electro-optical properties and other important physical properties such as a high work function, good thermal stability… FTO thin films have already been shown to act as an efficient transparent electrode in solar cells. In this work, FTO thin films were grown by ultrasonic spray pyrolysis on glass and flexible polymer substrates. The structural, electronic and optical properties of these FTO layers were thoroughly investigated. Our work focuses on a better understanding of their electro-optical properties, in terms for instance of electron scattering. We show that FTO layers (when combined with ZnO nanoparticles) exhibit haze factor as high as 60%, whilst maintaining very good electro-optical properties. The integration into solar cells is also presented. [less ▲]

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See detailPhysical properties of silver nanowire networks: effects of percolation and thermal annealing
Langley, Daniel ULg; Lagrange, Mélanie; Giusti, Gael et al

Conference (2014)

Silver nanowire networks have recently been a heavily researched subject due to their potential use as transparent electrodes in solar cells or flat panel displays. Currently, the most commonly used ... [more ▼]

Silver nanowire networks have recently been a heavily researched subject due to their potential use as transparent electrodes in solar cells or flat panel displays. Currently, the most commonly used material for such applications (Tin-doped Indium oxide) suffers from two major drawbacks: indium scarcity and brittleness. However, metallic nanowire networks can be deposited by low cost deposition techniques and exhibit simultaneously very promising optical, electrical and electro-mechanical properties. To enhance these properties, nanowire density should be considered. For a given nanowire aspect ratio, lower nanowire densities result in higher optical transparency but demonstrate lower electrical conductivity. As the density of nanowires is increased the relationship is reversed, resulting in high electrical conductivity but low optical transparency. Numerical Montecarlo simulations on stick percolation shed light on the percolative nature of these 2D networks. Relations between simulation and experimental observations are discussed. We also show that thermal annealing can efficiently improve the electrical properties without significantly changing the optical response2. However, above a certain temperature threshold, morphological instabilities occur and induce a cancelling out of the beneficial effects. The physical mechanisms involved in thermal annealing of Ag nanowire networks are addressed as well as their effects on electro-optical properties. Finally the potential integration of Ag nanowire networks into devices is evaluated. [less ▲]

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