Mist chemical vapour deposition of tin oxide thin films and nanostructures
| dc.contributor.author | Scott, Jonty | |
| dc.date.accessioned | 2020-03-30T00:56:33Z | |
| dc.date.available | 2020-03-30T00:56:33Z | |
| dc.date.issued | 2019 | en |
| dc.description.abstract | High quality thin films and novel square nanotubes of SnO2 were produced by the straightforward technique of mist chemical vapour deposition (Mist-CVD). Mist-CVD is a non-vacuum, solution-based process that involves the gas-assisted transport of ultrasonically-generated aerosols, which for SnO2 deposition, were from a simple aqueous Sn precursor solution. This bodes well for Mist-CVD growth of SnO2 as an environmentally friendly and cost effective alternative for current industrial production processes. This thesis displays results from the optimisation of deposition parameters and characterization of the SnO2 thin films and nanotubes produced by Mist-CVD. Through optimization of the parameters involved with the deposition, the highest quality, Mist-CVD deposited, SnO2 thin film was produced. X-ray diffraction measurements confirmed the rutile phase of SnO2, while also suggesting an epitaxial relationship with the substrate. In comparison to other atmospheric-based techniques, the Mist-CVD produced SnO2 films were amongst the smoothest and most optically, however the films were too insulating for practical use as a transparent conductive oxide. To increase the conductivity of Mist-CVD grown SnO2 thin films, their electrical properties were tuned through the addition of a precursor in the growth solution containing Sb, a typical n-type donor in SnO2. The films could be varied from insulating to semi-metallic via the Sb doping, with a remarkable maximum mobility of 48.1 ± 0.1 cm2V-1s-1. Secondary ion mass spectrometry and Hall effect measurements revealed that almost all the Sb atoms forming shallow substitutional donors on the Sn-site, each providing a single charge carrier to the conduction band. While x-ray diffraction, and UV-vis transmission measurements showed that the crystal structure, and optical transparency of the films did not deteriorate with the inclusion of the Sb ions, An exciting new growth mode of SnO2 materials was discovered through the formation of novel crystalline square nanotubes. This thesis exhibits the first pristine SnO2 nanotubes, with controllable orientation due to the epitaxial relationship with the substrate, successful doping and the first investigations on the hydroxylated surface termination of the (110) surfaces. The formation of these structures was strictly dependent on the addition of an e-beam evaporated Au thin film on the surface of the substrate, which de-wet into nanoparticles when heated, prior to the Mist-CVD deposition. Transmission electron microscopy measurements found the nanotubes were single crystal rutile SnO2, which grew in the (001) orientation, with the side surfaces being the (110) termination. The tube length and wall thickness were both found to be uniquely dependent on the deposition time and Sn precursor concentration, respectively. Furthermore, the tube formation was sensitive to changes in the substrate temperature, and Au nanoparticle size and distribution. For the first time, the hydroxyl termination on the (110) surface of these SnO2 nanotubes was probed using x-ray photoelectron spectroscopy, and both their removal, and a possible O- state, was observed after annealing in vacuum. These structures were also confirmed to be doped by measuring a current between two contacts bridged by a singular nanotube. This nanotube was grown with the addition of a Sb precursor, and a rough calculation of its resistivity matched that measured for the grown thin films with similar doping concentrations. Their confirmed conductivity opens a wide range of potential applications and experiments, making them an exciting and important discovery for this field. | en |
| dc.identifier.uri | https://hdl.handle.net/10092/100065 | |
| dc.identifier.uri | http://dx.doi.org/10.26021/8794 | |
| dc.language | English | |
| dc.language.iso | en | |
| dc.publisher | University of Canterbury | en |
| dc.rights | All Rights Reserved | en |
| dc.rights.uri | https://canterbury.libguides.com/rights/theses | en |
| dc.title | Mist chemical vapour deposition of tin oxide thin films and nanostructures | en |
| dc.type | Theses / Dissertations | en |
| thesis.degree.discipline | Physics | |
| thesis.degree.grantor | University of Canterbury | en |
| thesis.degree.level | Doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |
| uc.bibnumber | 2833451 | |
| uc.college | Faculty of Science | en |