Degree Type

Dissertation

Date of Award

2004

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

First Advisor

Palaniappa A. Molian

Abstract

Femtosecond pulsed laser (FPL) micromachining is a direct-writing technique in which an ultrashort pulse laser beam is focused to dimensions of a few microns inside or on the surface of the substrate and then moved around using a X-Y positioning table, thereby creating either features or patterns as required. It outperforms conventional micromachining technologies due to advantages such as precise resolution, minimal thermal or shock damage, and absence of discrimination among materials. 3C-SiC is a very important semiconductor in electronics and opto-electronics and more recently regarded as an optimal candidate for structural or coating applications in microelectromechanical systems (MEMS) used under harsh and high-temperature environments. However, it is a very difficult material to be machined or etched by mechanical or chemical methods.;In this work, fundamental studies on the interaction of femtosecond pulsed beam with 3C-SiC films were performed. The influence of laser parameters such as pulsed energy on the ablation and calculations of damage thresholds and ablation rates were determined. Based on these results, MEMS structures including micromotors, microturbine rotors, and lateral resonators were patterned with good quality and repeatability. Research demonstrates that FPL micromachining is capable of offering a unique solution to overcome the traditional barriers in SiC machining method, opening up opportunities for SiC materials to be used in industrial environment.;As a spinoff of femtosecond pulse micromachining, nanostructuring of 3C-SiC films on Si was observed. Nanoparticle surfaces were further studied in terms of formation conditions and characterizations of crystal structure and related properties. "Incubation" effects were identified and Coulomb explosion mechanism was proposed to be responsible for the generation of nanoparticles.;Results of research enhance our current understanding of ultrashort pulse-matter interactions and offer potential applications for SiC-MEMS.

DOI

https://doi.org/10.31274/rtd-180813-35

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu

Copyright Owner

Yuanyuan Dong

Language

en

Proquest ID

AAI3158327

File Format

application/pdf

File Size

145 pages

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