Degree Granting Department
Ashok Kumar, Ph.D.
Chemical vapor deposition, Cutting tools, WC-Co, Biosensor, Nanowires
In this thesis, a systematic study has been carried out on the synthesis, characterization and applications of microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) thin films deposited by the chemical vapor deposition (CVD) method. Firstly, an overview of diamond films synthesized from carbon-containing gas plasmas is presented. A parameter study was performed to grow diamond thin films. The transition from micro- to nanocrystallinity of diamond grains was achieved by controlling the Ar/Hydrogen gas ratio. The nanocrystallinity is the result of a new growth mechanism which involves the insertion of carbon dimmer into carbon-carbon and carbon-hydrogen bonds. Secondly, characterization of diamond films has been carried out by different techniques including electron microscopy, near edge X-ray absorption fine structure (NEXAFS), nanoindentation, and Raman spectroscopy.
Unique properties of NCD, compared to those of MCD grown by conventional hydrogen rich plasma, have been observed and investigated. Thirdly, various applications of diamond films are discussed: a). Well-adhered MCD coatings have been deposited on WC-Co substrates with proper surface pretreatment. A diffusion barrier Cr/CrN/Cr was deposited on the cemented carbide substrate and the substrate was short peened with 150 micron friable diamond powders to achieve higher nucleation density and stronger adhesion strength; b). A nitrogen doped NCD based biosensor was fabricated for glucose sensing. Carboxyl functional group and conducting polymer (polyaniline) have been utilized respectively to electrochemically functionalize the diamond surface. A linear response to glucose concentration has been obtained from the electrode with good sensitivity and stability; c). A novel approach to synthesize NCD wires has been developed for the first time.
The NCD coating was successfully coated on Si nanowires (SiNWs) to form NCD wire with diameter around a few microns. This study opens a whole new area for applications based on diamond wires such as neural transmission electrodes, field emission emitters, and electrochemical electrodes with improved properties
Scholar Commons Citation
Xu, Zhenqing, "Synthesis, characterization, and applications of CVD micro- and nanocrystalline diamond thin films" (2007). Graduate Theses and Dissertations.