References of "Nguyen, Ngoc Duy"
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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 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)

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 detailStudy of the energy distribution of the interface trap density in a GeSn MOS structure by numerical simulation of the electrical characteristics
Baert, Bruno ULg; Schmeits, Marcel ULg; Nguyen, Ngoc Duy ULg

in Applied Surface Science (2014), 291

Using a custom-made numerical simulation tool, we performed a systematic study of the energy distribution of the interface trap density in a GeSn MOS structure and of their effect on the electrical ... [more ▼]

Using a custom-made numerical simulation tool, we performed a systematic study of the energy distribution of the interface trap density in a GeSn MOS structure and of their effect on the electrical characteristics such as C–V and impedance spectra. Interface traps with various densities of states and energies in the bandgap have been investigated and the application of the conductance method was assessed. Based on a theoretical analysis, we obtained, as key results, direct connections between microscopic parameters of the structures and experimentally accessible features of the simulated macroscopic quantities. A straightforward relationship between the interface state density and the peaks in the conductance response is also highlighted. The dependence of the peak characteristics on the trap states was identified, as well as the effects of traps extending over large energy ranges in the bandgap. [less ▲]

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See detailStability of templated and nanoparticles dye-sensitized solar cells : photovoltaic and electrochemical investigation of degradation mechanisms at the photoelectrode interface
Dewalque, Jennifer ULg; Nguyen, Ngoc Duy ULg; Colson, Pierre ULg et al

in Electrochimica Acta (2014), 115(1), 478-486

A key issue in the commercialization of dye-sensitized solar cells is to maintain high efficiency and long lifetime. As reported in the literature, dye-sensitized solar cells are stable under visible ... [more ▼]

A key issue in the commercialization of dye-sensitized solar cells is to maintain high efficiency and long lifetime. As reported in the literature, dye-sensitized solar cells are stable under visible light soaking but thermal stress and UV exposure lead to efficiency degradation. However, all the stability studies published so far have been performed on cells whose TiO2 electrodes were prepared by tape casting or screen printing of nanoparticle pastes/inks. The present study concerns cells based on highly porous templated TiO2 electrodes, whose larger surface area could enhance the negative effects of thermal stress, light soaking and UV exposure. The long-term stability of these cells is compared with a classical nanoparticle-based cell using current-voltage measurements (I-V curves) and electrochemical impedance spectroscopy. Due to their higher active interface, templated cells are more sensitive than nanoparticle cells to UV illumination, although this can be easily solved in both cases by the use of a UV filter. The templated cells are as stable as the nanoparticle cells under visible light soaking (UV filtered). However, we showed that templated cells are more stable under thermal stress. Moreover, as evidenced by electrochemical impedance spectroscopy, templated cells show lower transfer resistance, as well as lower recombination resistance compared to nanoparticle cells. The crystallite connectivity promoted by the templating route seems to favor the electron transfers inside the porous layer. Using templated films in dye-sensitized solar cells is therefore really promising because higher conversion efficiencies are reached without promoting cell degradation. [less ▲]

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See detailNumerical simulation of the electrical characteristics of CIGS/CdS/ZnO solar cell heterostructures
Amand, Julien ULg; Nguyen, Ngoc Duy ULg

Poster (2013, December 03)

The electrical characteristics of CIGS-based solar cell heterostructure have been simulated by numerically solving the basic semiconductor equations by means of a finite differences method based on a ... [more ▼]

The electrical characteristics of CIGS-based solar cell heterostructure have been simulated by numerically solving the basic semiconductor equations by means of a finite differences method based on a Scharfetter-Gummel discretization scheme. The electric potential, electric field, carrier concentrations, current densities and recombination rates are obtained as function of the space coordinate and the bias voltage. Starting with the analysis of a single absorber layer structure sandwiched between two metal electrodes, we subsequently studied the properties of the CIGS/ZnO pn heterojunction and the influence of the buffer layer thickness in the CIGS/CdS/ZnO on the cell electrical response. A special focus was also given to the influence of grain boundaries in the bulk of CIGS depending on the defects nature and concentration. Electrical measurements including admittance spectroscopy were performed on samples for comparison to be further lead. Motivations This research is part of the project IQuaReS (Innovative in-line Quality control for Renewable Solar solutions) that aims to develop an in-line quality control tool for manufactured CIGS-based solar cells, based on electrical and optoelectrical, preferably non-invasive measurement methods. Exploratory simulations aim to isolate signature patterns that could be sought in experimental measurements . [less ▲]

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See detailNumerical simulation of the electrical characteristics of CIGS/CdS/ZnO solar cell heterostructures
Amand, Julien ULg; Nguyen, Ngoc Duy ULg

Poster (2013, September 17)

The electrical characteristics of CIGS-based solar cell heterostructure have been simulated by numerically solving the basic semiconductor equations by means of a finite differences method based on a ... [more ▼]

The electrical characteristics of CIGS-based solar cell heterostructure have been simulated by numerically solving the basic semiconductor equations by means of a finite differences method based on a Scharfetter-Gummel discretization scheme. The electric potential, electric field, carrier concentrations, current densities and recombination rates are obtained as function of the space coordinate and the bias voltage. Starting with the analysis of a single absorber layer structure sandwiched between two metal electrodes, we subsequently studied the properties of the CIGS/ZnO pn heterojunction and the influence of the buffer layer thickness in the CIGS/CdS/ZnO on the cell electrical response. A special focus was also given to the influence of grain boundaries in the bulk of CIGS depending on the defects nature and concentration. [less ▲]

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See detailSilver nanowire network : physical properties and effects of thermal treatments
Lagrange, Mélanie; Langley, Daniel ULg; Giusti, Gael et al

Conference (2013, September 16)

Detailed reference viewed: 29 (1 ULg)
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See detailTheoretical and experimental investigation of the GeSn bandgap
Shimura, Yosuke; Wang, Wei; Gencarelli, Federica et al

Conference (2013, September)

Detailed reference viewed: 36 (0 ULg)
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See detailElectrical Activity of Threading Dislocations and Defect Complexes in GeSn Epitaxial Layers
Gupta, Somya; Simoen, Eddy; Asano, Takanori et al

Conference (2013, June 04)

Detailed reference viewed: 101 (15 ULg)
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See detailBandgap Measurement by Spectroscopic Ellipsometry for Strained Ge1-xSnx
Shimura, Yosuke; Wang, Wei; Nieddu, Thomas ULg et al

Conference (2013, June 04)

Detailed reference viewed: 105 (3 ULg)
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See detailComposition and Thickness Dependence of GeSn Growth by Chemical Vapor Deposition
Wang, Wei; Shimura, Yosuke; Nieddu, Thomas ULg et al

Conference (2013, June 04)

Detailed reference viewed: 68 (1 ULg)
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See detailStudy of interface trap density in a GeSn MOS structure by numerical simulation of the electrical characteristics
Baert, Bruno ULg; Schmeits, Marcel ULg; Nguyen, Ngoc Duy ULg

Conference (2013, May)

The semiconducting alloy germanium tin (GeSn) is expected to play an important role in the development of high mobility channel materials for next generation CMOS and optoelectronic devices. The two most ... [more ▼]

The semiconducting alloy germanium tin (GeSn) is expected to play an important role in the development of high mobility channel materials for next generation CMOS and optoelectronic devices. The two most interesting features of this material, which is compatible with mainstream Si technology, are its tunable direct band-gap and the possibility to induce strain due to the lattice mismatch with Ge and Si, thereby increasing the holes and electrons mobilities. It has been shown that the interface trap density can be under- or overestimated in Ge-channel MOSFETs when applying conventional measurement techniques such as the conductance method. As this effect is common in low band-gap materials, we expect that it also occurs for GeSn. Following our previous work on metal/GeSn/Ge structures, we have therefore applied our home-built numerical simulation software to a metal/oxide/GeSn MOS structure in order to investigate the result of the presence of such interface states. We discuss possible effects of the interface trap density, interface trap energy and temperature on the electrical characteristics. Successive simulations of both the steady-state and ac small-signal regimes give access to measurable quantities such as the admittance spectrum and the C-V curves. A physical interpretation can be attributed to their variations and an overall comparison can be made with results obtained from equivalent electrical circuit analysis. [less ▲]

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See detailLong term stability of TiO2 templated multilayer films used as high efficiency photoelectrode in liquid DSSCs
Dewalque, Jennifer ULg; Nguyen, Ngoc Duy ULg; Henrist, Catherine ULg et al

Poster (2013, March)

To our knowledge, the stability results reported in the literature only concern cells made from classical doctor-bladed or screen-printed nanoparticles films. This study focuses on the comparison of the ... [more ▼]

To our knowledge, the stability results reported in the literature only concern cells made from classical doctor-bladed or screen-printed nanoparticles films. This study focuses on the comparison of the long-term stability of these cells with DSSCs working with templated mesoporous films. Indeed, the increased surface area of templated films could lead to a faster degradation of the resulting cells. In accordance with IEC:1646:1996 standard tests, light soaking test at 45°C has been applied to determine the cells stability under prolonged illumination. Moreover, thermal stress in the dark has been applied. Unfortunately, due to the sealing material heat resistance, thermal stress test was only performed at 45°C. [less ▲]

Detailed reference viewed: 109 (31 ULg)
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See detailCollection Efficiency and Design Requirements for Metallic Nanowire Networks in Solar Cells
Langley, Daniel ULg; Giusti, Gael; Nguyen, Ngoc Duy ULg et al

Poster (2013)

In using TCMs based on metallic nanowires it is important to determine the effect of nanowire geometry and spatial arrangement on the resulting network. To this end we have extensively simulated the ... [more ▼]

In using TCMs based on metallic nanowires it is important to determine the effect of nanowire geometry and spatial arrangement on the resulting network. To this end we have extensively simulated the effect of wire length and device size on the percolation properties of the network produced. We have performed Monte Carlo simulations of 2D conductive stick networks including for the first time stick lengths approximating nanowires which are produced experimentally. Each simulation is performed based on an average stick length but the actual lengths of the nanowires in the simulation are randomly generated with a normal distribution around the defined average length. The effects of density and length distribution on the percolation threshold are also explored. The results of such simulations are also employed to determine an elementary representative volume, which can be directly applied to a device design by allowing the determination of the nanowire density required to produce a conductive network associated with a characteristic length, such as diffusion length or pixel size. We also extend this work to the specific application of metallic nanowire networks as front electrodes in dye sensitized solar cells (DSSC), allowing a calculation of the collection efficiency as a function of network density. These calculations were based on the diffusion length of electrons generated within a DSSC and a spatial mapping of the collection efficiency function on the solar cell surface. [less ▲]

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See detailImpedance Spectroscopy of GeSn-based Heterostructures
Baert, Bruno ULg; Nakatsuka, Osamu; Zaima, Shigeaki et al

in ECS Transactions (2013), 50(9), 481-490

In this work, we investigated the electrical characteristics of p-GeSn/p-Ge and p-GeSn/n-Ge structures obtained by simulation of the basic semiconductor equations. We developed a numerical formalism based ... [more ▼]

In this work, we investigated the electrical characteristics of p-GeSn/p-Ge and p-GeSn/n-Ge structures obtained by simulation of the basic semiconductor equations. We developed a numerical formalism based on a drift-diffusion model including a trap level and applied it to typical GeSn-based heterostructures by focusing on the electrical response under small-signal alternating current regime. The results demonstrate that our method provides an access to both microscopic and macroscopic properties, and thereon, to a physical interpretation of the electrical characteristics of GeSn-based structures by linking measurable quantities to micro-scale variations in the structures. [less ▲]

Detailed reference viewed: 111 (39 ULg)
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See detailElectrical investigation of TCMs: role of structural defects and external stress
Langley, Daniel ULg; Giusti, Gael; Consonni, Vincent et al

Conference (2012, October 24)

Detailed reference viewed: 19 (5 ULg)