Nanoscale electronic properties of conjugated polymers and nanocrystals

O'Brien, Garret

Nanoscale electronic properties of conjugated polymers and nanocrystals

dc.check.embargoformat	Not applicable	en
dc.check.info	No embargo required	en
dc.check.opt-out	Not applicable	en
dc.check.reason	No embargo required	en
dc.check.type	No Embargo Required
dc.contributor.advisor	Quinn, Aidan J.	en
dc.contributor.advisor	Redmond, Gareth	en
dc.contributor.author	O'Brien, Garret
dc.date.accessioned	2013-09-03T08:47:04Z
dc.date.available	2013-09-03T08:47:04Z
dc.date.issued	2006
dc.date.submitted	2006
dc.description.abstract	The objective of this thesis is the exploration and characterisation of the nanoscale electronic properties of conjugated polymers and nanocrystals. In Chapter 2, the first application of conducting-probe atomic force microscopy (CP-AFM)-based displacement-voltage (z-V) spectroscopy to local measurement of electronic properties of conjugated polymer thin films is reported. Charge injection thresholds along with corresponding single particle gap and exciton binding energies are determined for a poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] thin film. By performing measurements across a grid of locations on the film, a series of exciton binding energy distributions are identified. The variation in measured exciton binding energies is in contrast to the smoothness of the film suggesting that the variation may be attributable to differences in the nano-environment of the polymer molecules within the film at each measurement location. In Chapter 3, the CP-AFM-based z-V spectroscopy method is extended for the first time to local, room temperature measurements of the Coulomb blockade voltage thresholds arising from sequential single electron charging of 28 kDa Au nanocrystal arrays. The fluid-like properties of the nanocrystal arrays enable reproducible formation of nanoscale probe-array-substrate junctions, allowing the influence of background charge on the electronic properties of the array to be identified. CP-AFM also allows complementary topography and phase data to be acquired before and after spectroscopy measurements, enabling comparison of local array morphology with local measurements of the Coulomb blockade thresholds. In Chapter 4, melt-assisted template wetting is applied for the first time to massively parallel fabrication of poly-(3-hexylthiophene) nanowires. The structural characteristics of the wires are first presented. Two-terminal electrical measurements of individual nanowires, utilising a CP-AFM tip as the source electrode, are then used to obtain the intrinsic nanowire resistivity and the total nanowire-electrode contact resistance subsequently allowing single nanowire hole mobility and mean nanowire-electrode barrier height values to be estimated. In Chapter 5, solution-assisted template wetting is used for fabrication of fluorene-dithiophene co-polymer nanowires. The structural characteristics of these wires are also presented. Two-terminal electrical measurements of individual nanowires indicate barrier formation at the nanowire-electrode interfaces and measured resistivity values suggest doping of the nanowires, possibly due to air exposure. The first report of single conjugated polymer nanowires as ultra-miniature photodetectors is presented, with single wire devices yielding external quantum efficiencies ~ 0.1 % and responsivities ~ 0.4 mA/W under monochromatic illumination.	en
dc.description.status	Not peer reviewed	en
dc.description.version	Accepted Version
dc.format.mimetype	application/pdf	en
dc.identifier.citation	O'Brien, G. 2006. Nanoscale electronic properties of conjugated polymers and nanocrystals. PhD Thesis, University College Cork.	en
dc.identifier.uri	https://hdl.handle.net/10468/1232
dc.language.iso	en	en
dc.publisher	University College Cork	en
dc.rights	© 2006, Garret O'Brien	en
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/3.0/	en
dc.subject	Nanoscale electronic properties	en
dc.subject	Scanning probe microscopy	en
dc.subject.lcsh	Nanocrystals	en
dc.subject.lcsh	Conjugated polymers	en
dc.subject.lcsh	Electronic structure	en
dc.subject.lcsh	Atomic force microscopy	en
dc.thesis.opt-out	false
dc.title	Nanoscale electronic properties of conjugated polymers and nanocrystals	en
dc.type	Doctoral thesis	en
dc.type.qualificationlevel	Doctoral	en
dc.type.qualificationname	PhD (Science)	en
ucc.workflow.supervisor	cora@ucc.ie