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Subject = Electron transport;
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Displaying Results 1 - 9 of 9 on page 1 of 1
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Computational modeling of defects in nanoscale device materials
(2014)
Greene-Diniz, Gabriel
Computational modeling of defects in nanoscale device materials
(2014)
Greene-Diniz, Gabriel
Abstract:
This PhD thesis concerns the computational modeling of the electronic and atomic structure of point defects in technologically relevant materials. Identifying the atomistic origin of defects observed in the electrical characteristics of electronic devices has been a long-term goal of first-principles methods. First principles simulations are performed in this thesis, consisting of density functional theory (DFT) supplemented with many body perturbation theory (MBPT) methods, of native defects in bulk and slab models of In0.53Ga0.47As. The latter consist of (100) - oriented surfaces passivated with A12O3. Our results indicate that the experimentally extracted midgap interface state density (Dit) peaks are not the result of defects directly at the semiconductor/oxide interface, but originate from defects in a more bulk-like chemical environment. This conclusion is reached by considering the energy of charge transition levels for defects at the interface as a function of distance from ...
http://hdl.handle.net/10468/2046
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Correlated electron transport across atomic and molecular tunnel junctions
(2018)
McDermott, Shane
Correlated electron transport across atomic and molecular tunnel junctions
(2018)
McDermott, Shane
Abstract:
As transistors continue to miniaturise the importance of describing electronics on an atomic scale increases. A molecular junction consists of a molecule connected to to metal electrodes via linker molecules and may be thought of as the prototype system for electronics on a few nanometre length scale. For charge transport calculations such systems are usually treated with a single particle approximation such as NEGF+DFT non-equilibrium Green’s function plus density functional theory. Typical single particle treatments are incomplete due to approximations made in the treatment of the electronic structure leading to discrepancies between theory and experiment by orders of magnitude, believed to be due to electron correlation. A solution to this is an accurate many body treatment of charge transport explicitly accounting for electron correlation. In this thesis the comparison of many body method MECS (Many Electron Correlated Scattering) to experiment and single particle methods, in pa...
http://hdl.handle.net/10468/6996
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Enantiomeric conformation controls rate and yield of photoinduced electron transfer in DNA sensitized by Ru(II) dipyridophenazine complexes
(2020)
Keane, Páraic M.; Poynton, Fergus E.; Hall, James P.; Quinn, Susan J.; et al.
Enantiomeric conformation controls rate and yield of photoinduced electron transfer in DNA sensitized by Ru(II) dipyridophenazine complexes
(2020)
Keane, Páraic M.; Poynton, Fergus E.; Hall, James P.; Quinn, Susan J.; et al.
Abstract:
Photosensitized oxidation of guanine is an important route to DNA damage. Ruthenium polypyridyls are very useful photosensitizers, as their reactivity and DNA-binding properties are readily tunable. Here we show a strong difference in the reactivity of the two enantiomers of [Ru(TAP)2(dppz)]2+, by using time-resolved visible and IR spectroscopy. This reveals that the photosensitized one-electron oxidation of guanine in three oligonucleotide sequences proceeds with similar rates and yields for bound Δ-[Ru(TAP)2(dppz)]2+, whereas those for the λ enantiomer are very sensitive to base sequence. It is proposed that these differences are due to preferences of each enantiomer for different binding sites in the duplex.
Irish Research Council
Science Foundation Ireland
University College Dublin
Royal Irish Academy/Royal Society exchange program
UK Biotechnology and Biological Sciences Research Council
http://hdl.handle.net/10197/11607
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Inosine Can Increase DNA′s Susceptibility to Photo‐oxidation by a RuII Complex due to Structural Change in the Minor Groove
(2020)
Keane, Páraic M.; Hall, James P.; Poynton, Fergus E.; Quinn, Susan J.; et al.
Inosine Can Increase DNA′s Susceptibility to Photo‐oxidation by a RuII Complex due to Structural Change in the Minor Groove
(2020)
Keane, Páraic M.; Hall, James P.; Poynton, Fergus E.; Quinn, Susan J.; et al.
Abstract:
Weinheim Key to the development of DNA-targeting phototherapeutic drugs is determining the interplay between the photoactivity of the drug and its binding preference for a target sequence. For the photo-oxidising lambda-[Ru(TAP)2(dppz)]2+ (Λ-1) (dppz=dipyridophenazine) complex bound to either d{T1C2G3G4C5G6C7C8G9A10}2 (G9) or d{TCGGCGCCIA}2 (I9), the X-ray crystal structures show the dppz intercalated at the terminal T1C2;G9A10 step or T1C2;I9A10 step. Thus substitution of the G9 nucleobase by inosine does not affect intercalation in the solid state although with I9 the dppz is more deeply inserted. In solution it is found that the extent of guanine photo-oxidation, and the rate of back electron-transfer, as determined by pico- and nanosecond time-resolved infrared and transient visible absorption spectroscopy, is enhanced in I9, despite it containing the less oxidisable inosine. This is attributed to the nature of the binding in the minor groove due to the absence of an NH2 group. ...
http://hdl.handle.net/10197/11614
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Properties of homo- and hetero-Schottky junctions from first principle calculations
(2018)
Greer, James C.; Blom, Anders; Ansari, Lida
Properties of homo- and hetero-Schottky junctions from first principle calculations
(2018)
Greer, James C.; Blom, Anders; Ansari, Lida
Abstract:
Electronic structure calculations for a homo-material semimetal (thick Sn)/semiconductor (thin Sn) heterodimensional junction and two conventional metal (Ag or Pt)/silicon hetero-material junctions are performed. Charge distributions and local density of states are examined to compare the physics of junctions formed by quantum confinement in a homo-material, heterodimensional semimetal junction with that of conventional Schottky hetero-material junctions. Relative contributions to the Schottky barrier heights are described in terms of the interface dipoles arising due to charge transfer at the interface and the effects of metal induced gap states extending into the semiconducting regions. Although the importance of these physical mechanisms vary for the three junctions, a single framework describing the junction energetics captures the behaviors of both the heterodimensional semimetal junction and the more conventional metal/semiconductor junctions.
http://hdl.handle.net/10468/9658
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Reduced workfunction intermetallic seed layers allow growth of porous n-GaN and low resistivity, ohmic electron transport
(2012)
Bilousov, Oleksandr V.; Carvajal, Joan J.; Drouin, Dominique; Mateos, Xavier; Diaz, Fra...
Reduced workfunction intermetallic seed layers allow growth of porous n-GaN and low resistivity, ohmic electron transport
(2012)
Bilousov, Oleksandr V.; Carvajal, Joan J.; Drouin, Dominique; Mateos, Xavier; Diaz, Francesc; Aguilo, Magdalena; O'Dwyer, Colm
Abstract:
Porous GaN crystals have been successfully grown and electrically contacted simultaneously on Pt- and Au-coated silicon substrates as porous crystals and as porous layers. By the direct reaction of metallic Ga and NH3 gas through chemical vapor deposition, intermetallic metal-Ga alloys form at the GaN–metal interface, allowing vapor–solid–solid seeding and subsequent growth of porous GaN. Current–voltage and capacitance–voltage measurements confirm that the intermetallic seed layers prevent interface oxidation and give a high-quality reduced workfunction contact that allows exceptionally low contact resistivities. Additionally, the simultaneous formation of a lower workfunction intermetallic permits ohmic electron transport to n-type GaN grown using high workfunction metals that best catalyze the formation of porous GaN layers and may be employed to seed and ohmically contact a range of III-N compounds and alloys for broadband absorption and emission.
http://hdl.handle.net/10468/6276
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Structural origins of conductance fluctuations in gold-thiolate molecular transport junctions
(2013)
RUNGGER, IVAN; SANVITO, STEFANO
Structural origins of conductance fluctuations in gold-thiolate molecular transport junctions
(2013)
RUNGGER, IVAN; SANVITO, STEFANO
Abstract:
We report detailed atomistic simulations combined with high-fidelity conductance calculations to probe the structural origins of conductance fluctuations in thermally evolving Aubenzene-1,4-dithiolate-Au junctions. We compare the behavior of structurally ideal junctions (electrodes with flat surfaces) to structurally realistic, experimentally representative junctions resulting from break junction simulations. The enhanced mobility of metal atoms in structurally realistic junctions results in significant changes to the magnitude and origin of the conductance fluctuations. Fluctuations are larger by a factor of 2-3 in realistic junctions compared to ideal junctions. Moreover, in junctions with highly deformed electrodes, the conductance fluctuations arise primarily from changes in the Au geometry, in contrast to results for junctions with non-deformed electrodes, where the conductance fluctuations are dominated by changes in the molecule geometry. These results provide important guida...
http://hdl.handle.net/2262/72988
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Supercritical-fluid synthesis of FeF2 and CoF2 Li-ion conversion materials
(2013)
Armstrong, Mark J.; Panneerselvam, Arunkumar; O'Regan, Colm; Morris, Michael A.; H...
Supercritical-fluid synthesis of FeF2 and CoF2 Li-ion conversion materials
(2013)
Armstrong, Mark J.; Panneerselvam, Arunkumar; O'Regan, Colm; Morris, Michael A.; Holmes, Justin D.
Abstract:
The synthesis of the Li-ion conversion candidates, FeF2 and CoF2, obtained from the single source organometallic precursors [Fe(tta)3] (tta = C8H4F3O2S), and [Co(hfac)2[middle dot]2H2O] (hfac = C5H1F6O2), respectively, via a novel supercritical fluid (SCF) method is presented. The nature of the synthesis led to highly-crystalline FeF2 and CoF2 powders requiring no additional thermal treatment. The as-obtained powders were investigated for use as potential positive Li-ion conversion electrodes by means of chronopotentiometric measurements. The FeF2 cells displayed high initial capacities following electrochemical conversion (up to [similar]1100 mA h g-1 at a potential of 1.0 V vs. Li/Li+), with appreciable cyclic behaviour over 25 discharge-charge cycles. The deposition of a [similar]5 nm layer of amorphous carbon onto the surface of the active material following SCF treatment, likely facilitated adequate electron transport through an otherwise poorly conducting FeF2 phase. Similarly...
http://hdl.handle.net/10468/2278
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Two-dimensional Schrodinger Scattering and Electron Transport in Graphene
(2014)
Blackledge, Jonathan; Rebow, Marek
Two-dimensional Schrodinger Scattering and Electron Transport in Graphene
(2014)
Blackledge, Jonathan; Rebow, Marek
Abstract:
Two-deimentional Born scatterin for the non-relativistic case is considered, the purpose being to investigate transport properties in mono-layer Graphene subject to an applied parallel electrical field. Solutions for the Probability Density Current (PDC) are obtained in the Fresnel zone which provides a model for simulating the PDC subject to membrane crumpling. In this context a Random Fractal Defect Model is considered which is used to assess the effect of (Fractal) crumpling on the PDC.
https://arrow.dit.ie/engscheleart2/108
Displaying Results 1 - 9 of 9 on page 1 of 1
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Dublin Institute of Technology (1)
Trinity College Dublin (1)
University College Cork (5)
University College Dublin (2)
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Doctoral thesis (2)
Journal article (7)
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Peer-reviewed (4)
Non-peer-reviewed (2)
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2020 (2)
2018 (2)
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2013 (2)
2012 (1)
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