No description available.

Diamond is a unique material with excellent properties. As a result of the development within the area of CVD synthesis, doping and surface functionalization, diamond has become a strong candidate for use in electrochemical, electronic and biomedical applications. In this thesis, theoretical calculations have been used with the purpose to investigate various properties of the diamond surfaces. The effect of doping elements (N and B) on the stability of different surface terminations with X (where X = H, OH, Oontop or Obridge) has been investigated for a diamond (100) surface. As a result, the adsorption energy for all termination types was shown to decrease from the situation with a non-doped diamond surface, to the scenario with a N- (or B-doped) diamond thin film.. This result was found to correlate well with the changes of the calculated Csurface-X bond lengths. Furthermore, the spin density has been calculated and used to show the local distribution of the unpaired electron, which is the consequence of the introduction of dopants into the diamond slab. As a result, the spin density was found to be localized in the vicinity to the dopants for H- (or OH-) terminated diamond (100) surfaces. On the other hand, a delocalised spin density over the Oadsorbate and Csurface layer for Oontop- and Obridge-terminated surfaces, has also been observed. Moreover, the results of the pDOS calculations indicate the electron donating ability of N, and the hole donating ability of B. The Fermi level was shifted towards the lower conduction band edge for N-doped diamond, and towards the upper edge of the valence band edge for B-doped diamond. Hence, N-doped diamond will render n-type conductivity, and B-doped diamond will show p-type conductivity. In addition, an interesting observation was made for Oontop –terminated diamond surfaces. Localized electron conductivity, involving only this type of termination situation,, was also observed for N- (or B-) doped and completely  Oontop-terminated diamond surfaces. With the purpose of applying diamond substrates in the formation of epitaxial graphene, the annealing process of an ideal diamond (111) surface has also been simulated in the present work. It was thereby shown that high temperatures (over 2000 K) will be required for the epitaxial formation of graphene ontop of the diamond (111) surface. However, in the presence of hydrogen radicals (by saturating the radical sites in the system), the required temperature was observed to decrease to 1000 K. In addition to these MD simulations, by using an interlayer iron ontop of the diamond (111) surface, the adhesion energies between the graphene and the Fe//diamond slab, as well as the adhesion energy between the graphene//Fe layer and the diamond (111) surface, have been calculated. Thereby, the interaction between the graphene and Fe layer was obtained to be very weak, and of an electrostatic type. On the other hand, the interaction between the Fe interlayer and the diamond substrate was calculated as a moderately strong covalent bond. Moreover, the changes in these interactions, correlating to the changes in the pDOS spectra of graphene, Fe and diamond, gave a tendency of one-dimensional quantum size effect, depending on the thickness of Fe interlayer.

No description available.

No description available.

Diamond-like carbon (DLC) thin films were produced by pulsed laser deposition (PLD) on silicon, fused silica, and silicon nitride substrates. The films produced were either undoped, made using a pure graphite target, or doped, using multi-component targets made from a combination of graphite and silicon, silicon nitride, titanium dioxide, or silicon monoxide. These films were evaluated for their potential use in biomedical applications, including coatings for artificial joints, heart stents, and bronchoscopes. The films were characterized by Raman spectroscopy, atomic force microscopy, ball-on-flat tribometry, contact angle measurements, and spectrophotometry. Film thickness was determined by optical profilometry. Film adhesion was checked by soaking the films in simulated body fluid (SBF) and monitoring the quality of the film surface at varying time intervals using an optical microscope. DLC coatings were produced with a root mean square surface roughness of less than 1 nm and a 0.08 lubricated coefficient of friction. Contact angles of water on the undoped films varied with deposition conditions, ranging from 65 to 88 degrees. Contact angles as low as 25 degrees were achieved by incorporating silicon monoxide dopant. DLC coatings were produced on fused silica having high transparency and showing no delamination after forty-three weeks of immersion in SBF. These results indicate that these films have potential as biomedical coatings.

The northern Churchill Province is an intensely explored, yet poorly researched target area for diamonds. I examined the mantle sources and residence history of diamonds from Aviat, located on the Melville Peninsula. Aviat diamonds display a δ13C range extending far below the average mantle value of -5‰ indicating eclogitic sources must be present. Crustal protoliths, carrying the organic matter implied by strongly 13C depleted diamond compositions, likely were supplied via subduction. The main population of diamonds around -5‰ may be either eclogitic or peridotitic. The CL patterns and variation of δ13C values within diamonds indicate that at least two diamond growth events, interrupted by periods of resorption, occurred at Aviat. Nitrogen and δ13C are decoupled indicating that multiple fluid sources contributed to diamond formation at Aviat. Mantle residence temperatures for most Aviat diamonds range from ~1050-1150⁰C, indicating a range of source depths.

This thesis presents theoretical and experimental study of properties of amorphous diamond-like carbon (DLC) coatings synthesised using discharge plasma methods. There were two objectives in this study. The first objective was to investigate the formation mechanism of hydrogenated DLC films (a-C:H) in an open hydrocarbon plasma source. The inductively coupled plasma (ICP) reactor was used to synthesise the films and the formation of sp2 and sp3 hybridised phases and the combination of these phases in the ICP plasma environment was studied. It was found that for a-C:H films with narrow distribution of the sp3 content the mechanical properties are determined by the degree of disorder of the sp2 fraction. The relationship between the sp3 content in fabricated films and hardness and Young's modulus was established. Raman and multi-wavelength (Vis – UV range) Raman spectroscopy was primarily used together with other suitable analytical methods to examine a-C:H films and it was found that films fabricated at higher ion energies displayed higher degree of clustering and bonding disorder than films produced at lower ion energies. All as fabricated a-C:H films were also found contain basic π-conjugated polymer inclusions as of trans-polyacetylene. The Raman results also reveal that the magnitude of Rayleigh scattered light is related to the relative density of the films, a feature that can be useful for monitoring film growth in-situ. The use of X-ray photoelectron spectroscopy (XPS) as a suitable method for measuring the sp3 content of the bulk DLC was also established. The second objective was to develop a fabrication technique that would allow fabrication of DLC films using graphite target sputtering with a single focused ion beam source and producing films with medium-high sp3 content. This research was motivated by the industrial partner of the project Laserdyne Pty Ltd that required a simple DLC deposition apparatus to be integrated into a standard, stand alone, optical thin film deposition chamber. Such technique was developed on the basis of a conventional ion beam target sputtering. In our experiments hydrogen-free DLC films with medium sp3 content were produced using a single, Kaufmann type ion source operated at low energies. The fabrication technique, denoted a reactive ion beam sputter deposition (RIBSD), was based on sputtering a graphite target at low incident angles and positioning the substrate at the grazing angles to the incoming ions, thus the incident ions (Ar and Xe ions were used) were simultaneously bombarding the target and the growing film. The effect of angle of incidence of an ion beam to the target and to the substrate in creating the sp3 content in DLC was investigated. It was found that the infringement bombardment of the substrate was not favourable for DLC growth as it essentially provided for a secondary re-sputtering process. Quality DLC films with approximately 40 % of the sp3 content were fabricated at the optimal angle of the ion flux to the target of 30º and to the substrate of 0º (parallel to the ion bema axis). The increased ion energy contributed to structural changes in DLC from predominantly sp2 graphitic like bonding to tetrahedral sp3 bonding arrangement.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 4 uppsatser.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references (leaves 89-99). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 97-102). Also available on the Internet.