Identifier

etd-11122004-093614

Degree

Doctor of Philosophy (PhD)

Department

Engineering Science (Interdepartmental Program)

Document Type

Dissertation

Abstract

Metal-containing, hydrogenated carbon films (Me-a-C:H) is a special class of nanocomposite films of particular interest since they can be multifunctional through the synergistic interaction of their individual components. Thus, nanocomposite thin films possess high potential in a wide field of engineering applications, especially in small scale devices. A series of multifunctional nanocomposite Co-a-C:H thin films have been synthesized by a hybrid chemical vapor deposition (CVD) and physical vapor deposition (PVD) process to uncover the relationship between synthesis, microstructure and properties. The effects of deposition parameters on the microstructural evolution and properties have been systematically studied. The results showed that the microstructure can be controlled through proper adjustment of the processing parameters, to produce Co in the shape of: nano particles, elongated particles, wormlike columns, self-assembled multilayers, self-assembled nano columns embedded in an amorphous a-C:H matrix. Self-assembly of Co nano columns in a-C:H is discovered. As-deposited Co-a-C:H thin films are composed of defect rich ε-Co encapsulated in a-C:H matrix. Regarding the properties, raising C content (reducing Co content) in the films improves their hardness and corrosion resistance and decreases friction and wear rate. All the Co-a-C:H films exhibit a low surface roughness. Nano columnar Co-a-C:H films show size-dependent magnetic behavior, such as superparamagnetic and perpendicular magnetism. Annealing studies reveal that the phase transitions of Co in Co-a-C:H film follow the sequence of Co-a-C:H film → (300 °C) ε-Co + δ ′–Co2C → (343 °C) hcp-Co + δ ′–Co2C → (407 °C) hcp-Co + graphite → (459 °C) fcc-Co + graphite. A mechanism and a zone diagram are presented to describe the microstructural evolution of Co-a-C:H films. Knowledge gained from this research allows the design and synthesis of nanocomposite Co-a-C:H films and other multifunctional systems of interest for new applications in the field of nanotechnology.

Date

2004

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Efstathios I. Meletis

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