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Title: Investigation of the optical and mechanical properties of III-V semiconductor nanowires
Author: Bradley, John
ISNI:       0000 0004 6421 8850
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2017
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This thesis concerns the theoretical and experimental study of three applications of III-V semiconductor nanowires. First, a detailed overview of the catalyst-free bottom-up growth of GaAs and InP nanowire arrays is presented. Control of nanowire radial and axial growth is demonstrated through tailoring of growth conditions and pre-growth fabrication methods. The limits of the catalyst-free growth technique are then investigated, leading to the establishment of an approach which allows for nanowire cross-section morphology to be precisely controlled. GaAs/InGaAs nanowire axial heterostructures are grown with elongated cross-section, resulting in the emission of strongly linearly polarised light from the nanowire top-facet. This represents the first demonstration of emission polarisation control in bottom-up semiconductor nanowires and provides a promising route for realisation of position-controlled linearly polarised single photon sources for quantum information applications. Control of nanowire morphology is also leveraged to enable investigation of the mechanical properties of catalyst-free GaAs nanowires with different cross-section aspect ratios. Bottom-up semiconductor nanowires show great promise as ultrasensitive nanomechanical resonators owing to their high structural quality and small motional mass. A slight random asymmetry in the hexagonal cross-section of regular nanowires which commonly arises as a result of small differences in the growth rates of the nanowire side facets, however, means that the direction of motion of the non-degenerate nanowire flexural modes cannot be determined \emph{a priori}. It is demonstrated that the ability to manipulate nanowire cross-section morphology allows for deterministic control of the direction of nanowire motion at the growth stage. Finally, a nanocavity design comprising an InP nanowire placed in a partially-etched GaAs photonic crystal slot waveguide is developed. Optimisation of the cavity design is performed using a combination of frequency-domain and FDTD simulations. After fabrication of photonic crystal slot waveguide devices using a top-down etching process, experimental realisation of the nanocavity design is achieved through nanomanipulation of individual nanowires deposited on the photonic crystal device substrate using an atomic force microscopy system. Such a cavity design provides potential for creation of high quality position-controlled nanowire photon sources integrated in GaAs photonic circuitry.
Supervisor: Wilson, Luke Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available