Schuurman, Joel2018-06-072018-06-072018http://hdl.handle.net/10092/15520http://dx.doi.org/10.26021/7582This research has investigated the surface modification and tunability of surface electrical properties of thin films of SnO2. SnO2 thin films were successfully modified with trifluoromethyl benzene diazonium tetrafluoroborate (CF3BD) and nitrobenzene diazonium tetrafluoroborate (NBD) modifiers via spontaneous self-assembly or electrochemical pathways and tridecafluorooctadecyl phosphonic acid (F13OPA), octadecylphosphonic acid (ODPA) and benzene pentafluoro phosphonic acid (PFBPA). The SnO2 substrates were mist chemical vapour deposition (CVD) and molecular beam epitaxy (MBE) grown, and were either un-doped or doped with Sb. Surfaces were characterised using both a laboratory based and Australian Synchrotron X-ray photoelectron spectroscopy (XPS) along with water contact angles (CA) and atomic force microscopy (AFM). Results from CA measurements revealed little change to surface wettability after modification but AFM measurements show an increase in the SnO2 surface roughness after modification. Furthermore, AFM in contact mode was used to scratch away a section of the modifying layer at the SnO2 surface allowing the layer thickness to be measured. The thickness was consistent with a multilayer for surfaces modified with aryl diazonium salts. XPS results revealed the presence of covalently bond aryl moieties and phosphonic acids at the SnO2 surface confirming successful surface modification by both class of modifiers. XPS was also used to measure changes to the low energy band edge of SnO2 surface after modification. From these spectra, changes in band bending were calculated. In most cases, no change or decrease in the downwards band bending for surfaces modified using aryl diazonium salts was observed and phosphonic acids gave an increase in downwards band bending. Further XPS analysis revealed that electrochemically initiated modification using CF3BD resulted in a higher surface concentration of modifiers than did spontaneous reaction. Additionally, the Sb dopant at SnO2 surfaces increased the apparent surface concentration of phosphonic acid modifiers over that at the un-doped surfaces. Doping also appeared to influence the grafting pathway for aryldiazonium ions and decreased the presence of azo links at modified surfaces.enAll Rights ReservedTheses / Dissertations