I joined the APRG in 2009 as a Ph.D. student. During the course of my Ph.D. studies I spent 12 months with the Condensed Matter Physics group under Prof. Jacek Furdyna at the University of Notre Dame, USA. My thesis, which was submitted in 2013, was titled Self-Assembled Arrays of Magnetic Nanostructures on Morphologically Patterned Semiconductor Substrates and is available here (PDF, 56MB).
My undergraduate degree in Theoretical Physics (first class honours, 79%) was also taken at Trinity College Dublin
I am currently working on a potential spin-out project based on power electronics and electrical monitoring. We have assembled a team with a great deal of experience and hope to have novel devices entering the market in the next 12-18 months.
Magnetic Nanowire arrays on Step-bunched Silicon
As part of my Ph.D. I fabricated self-assembled arrays of magnetic nanowires on step-bunched vicinal Si (111) templates. The first step involved an exploration of the step-bunching mechanism of vicinal Si, which results in a 'staircase' type morphology on the Si surface, consisting of flat (111) terraces and bunches of atomic steps.
The magnetic nanowires were then fabricated using a glancing angle deposition technique known as ATLAS (Atomic Terrace Low Angle Shadowing) which has been pioneered by this group. The technique was shown to be applicable to a range of different materials, with great control over parameters including wire thickness, separation and periodicity.
A large range of magnetic measurments were carried out on the resulting nanowire arrays, including temperature dependence, FMR, First Order Reversal Curves (FORCs) and Henkel Analysis. Phenomena investigated include shape anisotropy, magnetisation reversal mechanisms, interwire interactions, the presence of superparamagnetic particles and the effect of oxide capping layers.
Vertical GaAs nanowires were grown using the Vapour Liquid Solid (VLS) mechanism on GaAs (111) substrates during my time at the University of Notre Dame. For the first time in that group we tried to make ordered arrays of GaAs nanowires by using EBL defined Au nanodots as seed particles for nanowire growth, with good success.
A series of detailed examinations of the growth process under different conditions were carried out. Nanowires were grown under As2 and As4 fluxes, in Ga-limited and As-limited conditions, with patterned templates and unpatterned, and with a variety of values for separation and diameter of the catalyst nanodots.
In addition, some nanowire arrays were coated with a layer of Fe, and the effect of the unusual geometry on the resulting magnetic anisotropies of the system were examined using FMR.