Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/29571
Title: DIAMOND-LIKE CARBON (DLC) NANOCOMPOSITE: GROWTH MECHANISM AND MATERIAL PROPERTIES
Authors: FOONG YUAN MEI
Keywords: Diamond-like carbon (DLC) nancomposite, pulsed laser deposition, growth mechanism, material properties
Issue Date: 4-Jan-2011
Source: FOONG YUAN MEI (2011-01-04). DIAMOND-LIKE CARBON (DLC) NANOCOMPOSITE: GROWTH MECHANISM AND MATERIAL PROPERTIES. ScholarBank@NUS Repository.
Abstract: Diamond-like carbon (DLC) nanocomposite has been subjected to intense research efforts due to its superior and diversifiable properties. Although numerous studies have been performed to characterize the material properties of DLC, limited information is available on the growth mechanism of DLC nanocomposite. The primary objective of this work was to establish an understanding on the material properties and growth mechanism of DLC nanocomposite. To achieve this objective, a model based on the interaction of laser and DLC composite system that revealed the role of dopant in altering growth mechanism of DLC nanocomposite was explored. Based on the model, the presence of dopant was found to increase the energy absorbed by the composite system. With the energy absorbed from the interaction with laser, TRIM simulations showed that the formation of SiC can be enhanced while the excess energy can released as heat to graphitize sp<sup>3</sup> bonding and promote surface evolution when energetic ions impinged on substrate during deposition. By incorporating different dopants such as Er, Cu, Er<sub>2</sub>O<sub>3</sub> and ZnO and into DLC, the material properties of different DLC nanocomposite systems were examined. The presence of Er and Er<sub>2</sub>O<sub>3</sub> at low doping concentration was found to improve the adhesion property of DLC through the SiC formation. On the other hand, deposition using Zn/C and ZnO/C targets formed ZnO/DLC films but only ZnO/C targets yielded films with ~377 nm emission peak and improved mechanical properties. The absence of photoluminescence peak in Zn/C targets grown ZnO/DLC could be attributed to the reduced amount, yet more defective ZnO formed. By incorporating Cu into DLC, the electrical resistivity were found to decrease by orders of magnitude, and could serve as potential candidate for low cost field emitter when coated on Si nanocones. In addition, Er, Cu, Er<sub>2</sub>O<sub>3</sub>, Zn and ZnO dopants showed similar effects in reducing sp<sup>3</sup> content, increasing the adhesion strength, SiC bonding and surface roughness of DLC. As the presence of dopants in different nanocomposite systems showed similar effects in altering the surface and microstructure properties, the study was extended to examine material parameters that influenced the growth mechanism of DLC nanocomposites. By considering the role of dopants, interaction of laser and composite target and application of Saha¿s equation in the growth of DLC nanocomposite, the presence of dopants with reduced first ionization potential (<i>U</i>) and coefficient of extinction (<i>k</i>) was found to increase the energy absorbed and heat dissipation during deposition. As TRIM simulations showed that excess energy will be released as heat upon the impingement of ions on substrate, the heat may allow the metal ions to diffuse and bond with other ions to form nanoclusters, and graphitized the sp<sup>3</sup> bonding. By estimating the energy per ion using model based on <i>U</i> and <i>k</i>, the changes in microstructures and surface property on DLC doped with different metals predicted were in good agreement with experimental results. Hence, by identifying the material parameters of dopants that influenced the changes of microstructures and surface properties of DLC, this work may contribute to the prediction on properties changes in DLC nanocomposite.
URI: http://scholarbank.nus.edu.sg/handle/10635/29571
Appears in Collections:Ph.D Theses (Open)

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