Development of a high spatial resolution mapping technique for pristine and modified carbon surfaces using Scanning Auger Microscopy

Author: Jade Taylor

Taylor, Jade, 2021 Development of a high spatial resolution mapping technique for pristine and modified carbon surfaces using Scanning Auger Microscopy, Flinders University, College of Science and Engineering

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An area of ever-increasing importance in science, particularly in nanotechnology, is the development of environmentally friendly technologies to replace current materials. Carbon-based devices are being investigated for a huge range of applications, ranging from electronic devices to biological implants to plasma facing materials in fusion reactors. The usefulness of carbon stems from the changes in its physical and electrical properties that occur when the bonding and structure of the material changes. These differences allow for devices entirely composed of carbon to be created through the use of structures of one hybridisation of carbon on top of, or even within, another hybridisation.

In order to create these devices it is necessary to control the hybridisation of the carbon present in each section, and to be able to characterise the presence of the hybridisation with spatial resolution. These two areas have been the focus of the work presented in this dissertation, with plasma utilised for the growth or modification of carbon species, and the development of a technique to characterise the hybridisation of carbon with high spatial resolution using Scanning Auger Microscopy.

Plasma modification of a surface can produce a wide range of results depending on the conditions applied. The Radio Frequency (RF) coupling power applied to ignite the plasma from the source gas, the length of time the surface is exposed to the plasma, and the composition of the source gas itself are variables that can be controlled to modify the surface to varying extents. This work has shown systematic studies of the oxygen and argon plasma modification of HOPG that produces surface oxides and hybridisation changes to varying degrees, allowing for the selection of treatment parameters that will produce the desired surface.

Similar systematic studies have been performed on the plasma deposition of diamond like carbon films. The pressure of the source gas, the RF-coupling power used to ignite the plasma, and the exposure time of the substrate to the plasma all have an effect on the thickness and growth rate of the film, however the elemental and hybridisation composition of films grown from methane gas are constant despite variation of these parameters.

Mapping of the hybridisation of carbon materials at the micro- and nano-scales has been successfully performed using the technique developed within this work. The development of this technique involved the creation of code within MATLAB to process data obtained using Scanning Auger Microscopy, as well as the optimisation of the parameters used to acquire the data to achieve the best quality spectra in a reasonable acquisition time. This technique was expanded to include hybridisation line scanning so that higher spatial resolution in one dimension could be achieved with a shorter acquisition time than would be required for a 2D map of the same resolution, and both of these techniques have shown the ability to accurately and reproducibly determine the hybridisation of a carbon material with spatial resolution.

The development of the capabilities to grow and modify carbon materials and characterise them with spatial resolution has been established using the facilities available at Flinders University, and has provided an important step in the development carbon-based devices which is the ability to accurately determine their structure, and therefore their properties, at the micro- and nano-scales.

Keywords: x-ray photoelectron spectroscopy, scanning auger microscopy, carbon, graphite, diamond, diamond-like carbon, hybridisation, map, hybridisation map, spatial resolution, plasma, plasma modification

Subject: Physics thesis

Thesis type: Doctor of Philosophy
Completed: 2021
School: College of Science and Engineering
Supervisor: Professor Sarah Harmer