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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.

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.

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Diamond-like semiconductors are interesting materials to study due to the wide variety of technologically useful properties that these materials possess. These normal valence compounds have structures that are based on that of diamond, either the cubic or hexagonal polymorph. Though there are a finite number of possible compounds, due to isovalent and isoelectronic principles, the total number of potential compounds is quite extensive. Quaternary diamond-like semiconductors provide a unique opportunity, because much of the previous research has focused on binary and ternary systems leaving quaternary systems, relatively unexplored. Additionally, quaternary diamond-like semiconductors possess a greater degree of compositional flexibility compared to binary and ternary materials, which could result in the ability to more carefully tune desired physical properties. <br>In order to prepare the new materials, Li2ZnGeS4, Li2ZnSnS4, Li2CdGeS4, Li2CdSnS4 and Ag2MnSnS4, several synthetic methods have been employed, including high-temperature solid-state synthesis, polychalcogenide flux synthesis and solid-state microwave synthesis. The solid-state microwave synthetic method was itself studied using a number of target systems such as the ternary diamond-like semiconductor, AgInSe2. Additionally, several intermetallic compounds, such as Ag3In, AuIn2 and Bi2Pd were prepared using this procedure. Solid-state microwave synthesis is not as well known as some of the other synthetic methods that were employed in this work possibly due to a lack of understanding of the method, training and equipment. Despite these problems, the method has the potential to save time, energy and cost due to the unique nature of microwave heating. In an attempt to gain a better understanding of this synthetic method and its capabilities, the solid-state microwave synthetic method was used to prepare diamond-like semiconductors and intermetallic compounds. / Bayer School of Natural and Environmental Sciences / Chemistry and Biochemistry / PhD / Dissertation

Diamond-like semiconductors (DLSs) are a class of semiconductor materials having structures similar to that of either cubic or hexagonal diamond. These normal valence compounds are of interest for their wide variety of technologically useful properties that can be tuned for specific applications. Until recently, DLS research has been focused on binary and ternary compositions due to their relative ease of synthesis. However, quaternary DLSs have gained considerable popularity due to their increased compositional flexibility and their potential as multifunctional materials. Despite their growing reputation, the vast number of possible combinations and conceivable solid solutions, DLSs remain fairly unexplored.<br>This work focuses on quaternary DLSs of the formula Ag2-II-IV-S4 in order to advance the knowledge of structure-property relationships for this entire class of materials. Toward this goal, a more complete understanding of the crystal structures of these materials is necessary. This task is often problematic due to the presence of isoelectronic, or nearly isoelectonic elements, that can complicate X-ray structure refinements. In this work, Ag2CdGeS4 is used as a case study to demonstrate that this problem can be resolved with careful consideration of bonding environments as well as the use of high-resolution X-ray sources. For the novel DLS Ag2ZnSiS4, the relationship between the structure and optical properties is probed with the combination of single crystal X-ray diffraction, optical diffuse reflectance spectroscopy and electronic structure calculations using the software package Wien2k. Finally, the current set of predictive tools employed to forcast diamond-like structures are reviewed, including the adherence of these guidelines to the novel compound Ag2FeSiS4 as well all over 60 ternary and quaternary diamond-like materials currently reported in the literature. Furthermore, the most common radii sets used for the prediction of bond distance and cell parameters in these materials are compared to the observed bond distances in quaternary diamond-like nonoxide materials. / Bayer School of Natural and Environmental Sciences / Chemistry and Biochemistry / PhD; / Dissertation;

Diamond-like carbon (DLC) film exhibits an extreme hardness, low friction coefficient, chemical stability, heat conductivity, high resistance, and high optical transparency. There properties lead to remarkable on industrial applications Diamond-like carbon films were deposited onto the silicon (100) and ITO glass substrates. Under the same deposition conditions, the characteristics of DLC films were evaluated by the variations of deposited parameters such as the applied voltage, deposition temperature the concentrations of electrolyte; acetic acid. The properties due to the different substrate were compared and discussed in detail. In experimental work, the properties of DLC film were conducted by various measurements. Scanning electron microscopy can make an insight into the surface morphology also to reveal the uniformity of the DLC films. For the I-t curves of DLC film growth, it can be used to study of the growth mechanism by correlation the surface morphology observed by Scanning electron microscopy (SEM). The transmission, refraction index and optical band gap of DLC film was measured by the N &K analyzer. Finally, the hydrogen content, composition and microstructure of DLC films were characterized by the FTIR and XPS analyze According to above results, DLC film using the electrolyte of acetic acid was more difficult to deposit on Silicon substrate because the very high activation energy and the high hydrogen ion existing in DI water firstly deposited on the surface of Si substrate. For FTIR measurement, The absorption wavenumber of various bonding observed were positioned at 610 cm-1,680 cm-1,1100 cm-1 and 3600 cm-1~3800 cm-1and to be cauterized as the bonding of Si-H¡BSi-O and O-H, respectively. The absorption peaks within the range from 2800 cm-1 to 3100 cm-1 were missing. Peaks observed were attributed to the bonding of Si-C¡B SP3 C-C¡B C-O¡BC-C¡BC=O and C=C and the CHn bonding was missing on the surface of substrate. The reaction mechanism of DLC deposition can be suggested from the results of measurements. As bias voltage applied, the acetic ion; CH3COO- were attracted by the Anode as the state of C¡]Anode¡^-OOCCH3, and then to give electron and form the CH3+ion»PCO2. The hydrogen ion and methyl ion were attracted by cathode. The competitive reaction was built between ions to deposited DLC films and/or to form Si-H. However, experimental results show that the last was preferred and for forming the DLC film was forbidden.

Diamond-like Carbon (DLC) film exhibits an extreme hardness, low friction coefficient, chemical stability, heat conductivity, and high resistance. Their properties lead to remarkable applications on industry. In the experiment, we use electrondeposition to deposit the DLC film on Si substrate. Different concentrations of electrolyte were used to deposit on the of silicon substrates with different roughness surface. KOH solution was used to etch and to get the different roughness on the surface of silicon substrates. the morphology of surface were observed by SEM and AFM. Composition and microstructure of the DLC film were characterized by the Raman spectroscopy and XPS, repectively. The optical properties of DLC film were investigated by the N&K analyzer. From the AFM results, the surface morphology observed by KOH etching on the surface of silicon substrates during etching time as 0¡B20¡B40¡B60 min, the surface roughness increased from 2.64 to 14.07 nm. Based on thevariation of surface roughness, the growth rate was observed more quicker than the non etch surface. Moreover, to deposit the DLC film on the alkalinity solution was better then acid solution. However, the ID/IG ratio and the sp2/sp3 ratio obtained from Raman and XPS increase with the roughness surface from 1.09 to 1.82 and 0.985 to 2.15, respectively. It is because that the microstructure of DLC film varies and exchange to graphitization. The mixed the ammonia water and ammonium acetate into acetic acid solution was used to deposit DLC film on Si surface, and film shows with lower ID/IG ratio. Additionally, as the amount of ammonium acetate was varied in the solution, the ID/IG ratio of the films observed as decrease from 1.2 to 0.93 with increasing amount of ammonium acetate 10g to 40g. It was due to the methyl radicals increase in the solution. Besides, we can find the optical band gap decreased with DLC films changing to graphitization.

In order to obtain diamond-like carbon (DLC) thin films with improved mechanical, tribological, thermal and corrosion properties for practical applications, the structure and properties of various DLC thin films including hydrogen-free DLC, hydrogenated DLC, and DLC-MoS2 composites synthesized under different conditions were investigated in this thesis. The research methodologies and the main results are summarized in following paragraphs. Hydrogen-free DLC thin films were synthesized by biased target ion beam deposition (BTIBD) method, while hydrogenated DLC thin films were deposited by ion beam deposition technique using a Kaufman-type ion source and an end-Hall ion source. DLC-MoS2 composite thin films were also synthesized using BTIBD technique in which MoS2 was produced by sputtering a MoS2 target while DLC was simultaneously deposited by ion beam deposition. The influence of processing parameters on the bonding structure, morphology and properties of the deposited films was investigated using atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, synchrotron based near edge X-ray absorption fine structure spectroscopy, X-ray diffraction, scanning electron microscopy, nanoindentation, ball-on-disk and corrosion testing. Finally, the influence of annealing temperature on the structure and properties of pure DLC and DLC-MoS2 composite films in ambient air and low pressure environments was studied. In the case of BTIBD method, hydrogen-free DLC thin films with exceptionally high smoothness and low friction coefficient were prepared by biased target sputtering of graphite target without additional ion bombardment either by negative bias of substrate or assisting ion source. For ion beam deposition technique with Kaufman ion source, the DLC thin films synthesized at ion energies of 300 eV showed the highest sp3 content and optimum properties. Regarding end-Hall ion source, the best properties achieved in DLC films synthesized at ion energies of 100 eV. Comparing with pure DLC and pure MoS2 films, the DLC-MoS2 films deposited at low biasing voltages showed better tribological properties including lower coefficient of friction and wear coefficient in ambient air environment. Also, comparing with pure DLC films, the DLC-MoS2 thin films showed a slower rate of graphitization and higher structure stability throughout the range of annealing temperatures, indicating a relatively higher thermal stability.

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