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UBC Theses and Dissertations

Dimensional modification of vertically aligned carbon nanotubes using miniaturized arc and glow discharges Sarwar, Mirza Saquib us


There has been a significant rise in interest in carbon nanotube (CNT) structures to be implemented in micro electro mechanical systems (MEMS) devices owing to the appealing characteristics possessed by CNTs. Electrical discharges may be used to modify and machine CNT forests generating a myriad of applications from the treated structures. High current density arc discharge may be used to machine the CNT forest and generate micro structures while low current density glow discharge may be used to treat the CNT surface and change its characteristics for relevant applications. Techniques for fabricating CNT based MEMS are being developed for some time owing to the escalating demand, and have seen substantial progress over the years. The goal is to develop a technique that can provide precise machining with high throughput, and being economically feasible at the same time. This process employs an array of Cu electrodes microfabricated through an advanced UV-LIGA process enabled with a new photoresist system in combination with electroplating, providing a low-cost path to constructing high-density arrays of µEDM electrodes for high-throughput parallel processing. The fabricated arrays of 85-µm-tall electrodes are utilized to demonstrate and characterize planar dry µEDM for post-growth patterning of CNT forests in air. Die sinking and scanning processes are tested to show pattern transfers with a 4 µm tolerance and an average surface roughness of 230 nm. An elemental analysis suggests that contamination of the electrode material on the produced patterns is minimal. Key characteristics in the use of planar electrodes for batch processing of CNT forests are revealed through experimental analysis and discussed in detail. The results suggest that the investigated process is a promising approach toward offering a cost-effective manufacturing technology for future products functionalized with custom-designed microstrucutres of CNT forests. In addition to selectively manipulating the height of the CNT iii forest to generate desired structures for MEMS devices, research is conducted to modify the diameter of the nanotubes locally by means of glow discharge to attain further characteristic enhancements derived from such modified CNTs. Literature exists where CNTs have been treated by plasma (mostly for functionalization), but local treatment is a novel approach. The outcome of the research has given rise to results similar to literature where the diameter is decreased by rupturing of outer walls of MWCNT. In addition, extension of the research has resulted in coalesced structures that are reported for the first time. Further extension of the research to radio frequency discharge has been proposed and designed. It is postulated that such local configuration of characteristic parameters of CNT forest surface can have a number of applications in MEMS, electronics, and other possible fields.

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