Institutions
|
About Us
|
Help
|
Gaeilge
0
1000
Home
Browse
Advanced Search
Search History
Marked List
Statistics
A
A
A
Author(s)
Institution
Publication types
Funder
Year
Limited By:
Author = Lotty, Olan;
12 items found
Sort by
Title
Author
Item type
Date
Institution
Peer review status
Language
Order
Ascending
Descending
25
50
100
per page
Bibtex
CSV
EndNote
RefWorks
RIS
XML
Displaying Results 1 - 12 of 12 on page 1 of 1
Marked
Mark
Containing the catalysts: diameter controlled Ge nanowire growth
(2013)
Lotty, Olan; Biswas, Subhajit; Ghoshal, Tandra; Glynn, Colm; O'Dwyer, Colm; Petkov...
Containing the catalysts: diameter controlled Ge nanowire growth
(2013)
Lotty, Olan; Biswas, Subhajit; Ghoshal, Tandra; Glynn, Colm; O'Dwyer, Colm; Petkov, Nikolay; Morris, Michael A.; Holmes, Justin D.
Abstract:
Sub-20 nm diameter Ge nanowires with narrow size distributions were grown from Ag nanoparticle seeds in a supercritical fluid (SCF) growth process. The mean Ge nanowire diameter and size distribution was shown to be dependent upon Ag nanoparticle coalescence, using both spin-coating and a block copolymer (BCP) templating method for particle deposition. The introduction of a metal assisted etching (MAE) processing step in order to "sink" the Ag seeds into the growth substrate, prior to nanowire growth, was shown to dramatically decrease the mean nanowire diameter from 27.7 to 14.4 nm and to narrow the diameter distributions from 22.2 to 6.8 nm. Hence, our BCP-MAE approach is a viable route for controlling the diameters of semiconductor nanowires whilst also ensuring a narrow size distribution. The MAE step in the process was found to have no detrimental effect on the length or crystalline quality of the Ge nanowires synthesised.
http://hdl.handle.net/10468/2275
Marked
Mark
Detection of ultra-low protein concentrations with the simplest possible field effect transistor
(2019)
Georgiev, Yordan M.; Petkov, Nikolay; Yu, Ran; Nightingale, Adrian M.; Buitrago, Elizab...
Detection of ultra-low protein concentrations with the simplest possible field effect transistor
(2019)
Georgiev, Yordan M.; Petkov, Nikolay; Yu, Ran; Nightingale, Adrian M.; Buitrago, Elizabeth; Lotty, Olan; DeMello, John C.; Ionesco, Adrian M.; Holmes, Justin D.
Abstract:
Silicon nanowire (Si NW) sensors have attracted great attention due to their ability to provide fast, low-cost, label-free, real-time detection of chemical and biological species. Usually configured as field effect transistors (FETs), they have already demonstrated remarkable sensitivity with high selectivity (through appropriate functionalisation) towards a large number of analytes in both liquid and gas phases. Despite these excellent results, Si NW FET sensors have not yet been successfully employed to detect single molecules of either a chemical or biological target species. Here we show that sensors based on silicon junctionless nanowire transistors (JNTs), the simplest possible transistors, are capable of detecting the protein streptavidin at a concentration as low as 580 zM closely approaching the single molecule level. This ultrahigh detection sensitivity is due to the intrinsic advantages of junctionless devices over conventional FETs. Apart from their superior functionalit...
http://hdl.handle.net/10468/7934
Marked
Mark
Diameter-driven crossover in resistive behaviour of heavily doped self-seeded germanium nanowires
(2016)
Connaughton, Stephen; Koleśnik-Gray, Maria M.; Hobbs, Richard G.; Lotty, Olan; Holmes, ...
Diameter-driven crossover in resistive behaviour of heavily doped self-seeded germanium nanowires
(2016)
Connaughton, Stephen; Koleśnik-Gray, Maria M.; Hobbs, Richard G.; Lotty, Olan; Holmes, Justin D.; Krstić, Vojislav
Abstract:
The dependence of the resistivity with changing diameter of heavily-doped self-seeded germanium nanowires was studied for the diameter range 40 to 11 nm. The experimental data reveal an initial strong reduction of the resistivity with diameter decrease. At about 20 nm a region of slowly varying resistivity emerges with a peak feature around 14 nm. For diameters above 20 nm, nanowires were found to be describable by classical means. For smaller diameters a quantum-based approach was required where we employed the 1D Kubo–Greenwood framework and also revealed the dominant charge carriers to be heavy holes. For both regimes the theoretical results and experimental data agree qualitatively well assuming a spatial spreading of the free holes towards the nanowire centre upon diameter reduction.
http://hdl.handle.net/10468/3137
Marked
Mark
Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity
(2013)
McSweeney, William; Lotty, Olan; Mogili, N. V. V.; Glynn, Colm; Geaney, Hugh; Tanner, D...
Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity
(2013)
McSweeney, William; Lotty, Olan; Mogili, N. V. V.; Glynn, Colm; Geaney, Hugh; Tanner, David A.; Holmes, Justin D.; O'Dwyer, Colm
Abstract:
By using Si(100) with different dopant type (n++-type (As) or p-type (B)), we show how metal-assisted chemically etched (MACE) nanowires (NWs) can form with rough outer surfaces around a solid NW core for p-type NWs, and a unique, defined mesoporous structure for highly doped n-type NWs. We used high resolution electron microscopy techniques to define the characteristic roughening and mesoporous structure within the NWs and how such structures can form due to a judicious choice of carrier concentration and dopant type. The n-type NWs have a mesoporosity that is defined by equidistant pores in all directions, and the inter-pore distance is correlated to the effective depletion region width at the reduction potential of the catalyst at the silicon surface in a HF electrolyte. Clumping in n-type MACE Si NWs is also shown to be characteristic of mesoporous NWs when etched as high density NW layers, due to low rigidity (high porosity). Electrical transport investigations show that the et...
http://hdl.handle.net/10468/2408
Marked
Mark
Electrical characterization of high performance, liquid gated vertically stacked SiNW-based 3D FET biosensors
(2014)
Buitrago, Elizabeth; Badia, Monserrat Fernández-Bolaños; Georgiev, Yordan M.; Yu, Ran; ...
Electrical characterization of high performance, liquid gated vertically stacked SiNW-based 3D FET biosensors
(2014)
Buitrago, Elizabeth; Badia, Monserrat Fernández-Bolaños; Georgiev, Yordan M.; Yu, Ran; Lotty, Olan; Holmes, Justin D.; Nightingale, Adrian M.; Guerin, Höel M.; Ionescu, Adrian M.
Abstract:
A 3D vertically stacked silicon nanowire (SiNW) field effect transistor featuring a high density array of fully depleted channels gated by a backgate and one or two symmetrical platinum side-gates through a liquid has been electrically characterized for their implementation into a robust biosensing system. The structures have also been characterized electrically under vacuum when completely surrounded by a thick oxide layer. When fully suspended, the SiNWs may be surrounded by a conformal high-κ gate dielectric (HfO2) or silicon dioxide. The high density array of nanowires (up to 7 or 8 × 20 SiNWs in the vertical and horizontal direction, respectively) provides for high drive currents (1.3 mA/μm, normalized to an average NW diameter of 30 nm at VSG = 3 V, and Vd = 50 mV, for a standard structure with 7 × 10 NWs stacked) and high chances of biomolecule interaction and detection. The use of silicon on insulator substrates with a low doped device layer significantly reduces leakage cur...
http://hdl.handle.net/10468/2277
Marked
Mark
Fabrication and characterization of single-crystal metal-assisted chemically etched rough Si nanowires for lithium-ion battery anodes
(2011)
McSweeney, William; Lotty, Olan; Holmes, Justin D.; O'Dwyer, Colm
Fabrication and characterization of single-crystal metal-assisted chemically etched rough Si nanowires for lithium-ion battery anodes
(2011)
McSweeney, William; Lotty, Olan; Holmes, Justin D.; O'Dwyer, Colm
Abstract:
Silicon nanowires were fabricated by a metal assisted chemical (MAC) etching process and routes toward ohmic contacting of substrates for Li-ion battery anode application were developed. Si nanowire layers are comprised of wires that are single crystal with rough outer surfaces. The nanowires are epitaxial with the underlying Si(100) substrate, maintain equivalent doping density and crystal orientation, and are coated with a stoichiometric SiO2. Electrical backside contacting using an In-Ga eutectic allows low-resistance ohmic contacts to low-doped nanowire electrodes for electrochemical testing.
http://hdl.handle.net/10468/6295
Marked
Mark
Fully CMOS-compatible top-down fabrication of sub-50 nm silicon nanowire sensing devices
(2014)
Georgiev, Yordan M.; Petkov, Nikolay; McCarthy, Brendan; Yu, Ran; Djara, Vladimir; O...
Fully CMOS-compatible top-down fabrication of sub-50 nm silicon nanowire sensing devices
(2014)
Georgiev, Yordan M.; Petkov, Nikolay; McCarthy, Brendan; Yu, Ran; Djara, Vladimir; O'Connell, Dan; Lotty, Olan; Nightingale, Adrian M.; Thamsumet, Nuchutha; DeMello, John C.; Blake, Alan; Das, Samaresh; Holmes, Justin D.
Abstract:
This article reports the fabrication of sub-50 nm field effect transistor (FET)-type silicon (Si) nanowire (Si NW) chemical and biological sensing devices with a junctionless architecture, as well as on the initial characterisation of their electrical and sensing performance. The devices were fabricated using a fully complementary metal-oxide-semiconductor (CMOS)-compatible top-down process on silicon-on-insulator (SOI) wafers. The fabrication process was mainly based on high-resolution electron beam lithography (EBL) and reactive ion etching (RIE) but also included photolithography (mix-and-match lithography), thin film deposition by electron beam evaporation, lift-off, thermal annealing and wet etching. The sensing performance of a matrix of nanowire devices, i.e. containing 1, 3 and 20 NWs with lengths of 0.5, 1 and 10 μm was examined. Each element of the matrix also contained five devices with different NW widths: 10, 20, 30, and 50 nm and 5 μm (a Si belt reference device). Elec...
http://hdl.handle.net/10468/2274
Marked
Mark
Porous to non-porous transition in the morphology of metal assisted etched silicon nanowires
(2012)
Lotty, Olan; Petkov, Nikolay; Georgiev, Yordan M.; Holmes, Justin D.
Porous to non-porous transition in the morphology of metal assisted etched silicon nanowires
(2012)
Lotty, Olan; Petkov, Nikolay; Georgiev, Yordan M.; Holmes, Justin D.
Abstract:
A single step metal assisted etching (MAE) process, utilizing metal ion-containing HF solutions in the absence of an external oxidant, has been developed to generate heterostructured Si nanowires with controllable porous (isotropically etched) and non-porous (anisotropically etched) segments. Detailed characterisation of both the porous and non-porous sections of the Si nanowires was provided by transmission electron microscopy studies, enabling the mechanism of nanowire roughening to be ascertained. The versatility of the MAE method for producing heterostructured Si nanowires with varied and controllable textures is discussed in detail.
http://hdl.handle.net/10468/6705
Marked
Mark
Raman scattering spectroscopy of metal-assisted chemically etched rough nanowires
(2011)
Glynn, Colm; Lotty, Olan; McSweeney, William; Holmes, Justin D.; O'Dwyer, Colm
Raman scattering spectroscopy of metal-assisted chemically etched rough nanowires
(2011)
Glynn, Colm; Lotty, Olan; McSweeney, William; Holmes, Justin D.; O'Dwyer, Colm
Abstract:
Silicon nanowires were fabricated by a metal assisted chemical (MAC) etching process and routes toward ohmic contacting of substrates for Li-ion battery anode application were developed. Si nanowire layers are comprised of wires that are single crystal with rough outer surfaces. The nanowires are epitaxial with the underlying Si(100) substrate, maintain equivalent doping density and crystal orientation, and are coated with a stoichiometric SiO2. Electrical backside contacting using an In-Ga eutectic allows low-resistance ohmic contacts to low-doped nanowire electrodes for electrochemical testing.
http://hdl.handle.net/10468/6296
Marked
Mark
Self-seeded growth of germanium nanowires: coalescence and ostwald ripening
(2012)
Lotty, Olan; Hobbs, Richard; O'Regan, Colm; Hlina, Johann; Marschner, Christoph; O...
Self-seeded growth of germanium nanowires: coalescence and ostwald ripening
(2012)
Lotty, Olan; Hobbs, Richard; O'Regan, Colm; Hlina, Johann; Marschner, Christoph; O'Dwyer, Colm; Petkov, Nikolay; Holmes, Justin D.
Abstract:
We report the controlled self-seeded growth of highly crystalline Ge nanowires, in the absence of conventional metal seed catalysts, using a variety of oligosilylgermane precursors and mixtures of germane and silane compounds (Ge:Si ratios between 1:4 and 1:1). The nanowires produced were encased in an amorphous shell of material derived from the precursors, which acted to isolate the Ge seed particles from which the nanowires were nucleated. The mode diameter and size distribution of the nanowires were found to increase as the growth temperature and Ge content in the precursors increased. Specifically, a model was developed to describe the main stages of self-seeded Ge nanowire growth (nucleation, coalescence, and Ostwald ripening) from the oligosilylgermane precursors and, in conjunction with TEM analysis, a mechanism of growth was proposed.
http://hdl.handle.net/10468/6168
Marked
Mark
Semiconductor nanostructures for antireflection coatings, transparent contacts, junctionless thermoelectrics and Li-ion batteries
(2013)
Glynn, Colm; Osiak, Michal J.; McSweeney, William; Lotty, Olan; Jones, Kim; Geaney, Hug...
Semiconductor nanostructures for antireflection coatings, transparent contacts, junctionless thermoelectrics and Li-ion batteries
(2013)
Glynn, Colm; Osiak, Michal J.; McSweeney, William; Lotty, Olan; Jones, Kim; Geaney, Hugh; Quiroga-Gonzalez, Enrique; Holmes, Justin D.; O'Dwyer, Colm
Abstract:
Porous semiconductors structured top-down by electrochemical means, and from bottom-up growth of arrays and arrangements of nanoscale structures, are shown to be amenable to a range of useful thermal, optical, electrical and electrochemical properties. This paper summarises recent investigations of the electrochemical, electrical, optical, thermal and structural properties of porous semiconductors such as Si, In2O3, SnO2 and ITO, and dispersions, arrays and arrangements of nanoscale structures of each of these materials. We summarize the property-inspired application of such structurally engineered arrangements and morphologies of these materials for antireflection coatings, broadband absorbers, transparent contacts to LEDs that improve transmission, electrical contact and external quantum efficiency. Additionally the possibility of thermoelectric performance through structure-mediated variation in thermal resistance and phonon scattering without a p-n junction is shown through phon...
http://hdl.handle.net/10468/6136
Marked
Mark
The influence of carrier density and doping type on lithium insertion and extraction processes at silicon surfaces
(2014)
McSweeney, William; Lotty, Olan; Glynn, Colm; Geaney, Hugh; Holmes, Justin D.; O'D...
The influence of carrier density and doping type on lithium insertion and extraction processes at silicon surfaces
(2014)
McSweeney, William; Lotty, Olan; Glynn, Colm; Geaney, Hugh; Holmes, Justin D.; O'Dwyer, Colm
Abstract:
The Li+ insertion and extraction characteristics at n-type and p-type Si(100) electrodes with different carrier density and doping type are investigated by cyclic voltammetry and constant current measurements. The insertion and extraction potentials are demonstrated to vary with cycling and the occurrence of an activation effect is shown in n-type electrodes where the charge capacity and voltammetric currents are found to be much higher than p-type electrodes. A rate-dependent redox process influenced by the surface region electronic density, which influences the magnitude of cyclic voltammetry current is found at Si(100) surface regions during Li insertion and extraction. At p-type Si(100) surface regions, a thin, uniform film forms at lower currents, while also showing a consistently high (>70%) Coulombic efficiency for Li extraction. The p-type Si(100) surface region does not undergo crack formation after deintercalation and the amorphization was demonstrated using transmissio...
http://hdl.handle.net/10468/6115
Displaying Results 1 - 12 of 12 on page 1 of 1
Bibtex
CSV
EndNote
RefWorks
RIS
XML
Year
2019 (1)
2016 (1)
2014 (3)
2013 (3)
2012 (2)
2011 (2)
built by Enovation Solutions