Type of Document Dissertation Author Johnson, Stephen Lee URN etd-08082008-140048 Title Resonant-infrared laser ablation of polymers: mechanisms and applications Degree PhD Department Physics Advisory Committee
Advisor Name Title Richard F. Haglund, Jr. Committee Chair Eva Harth Committee Member Kenneth Schriver Committee Member Ronald Schrimpf Committee Member Shane Hutson Committee Member Keywords
- laser ablation
- infrared laser ablation
- pulsed-laser deposition
- polymer thin-films
Date of Defense 2008-08-07 Availability unrestricted AbstractResonant infrared (RIR) laser ablation of two model polymer systems is studied.
A tunable free-electron laser (FEL) operating in the mid-infrared is used to resonantly excite vibrational modes of polystyrene and poly(ethylene glycol) to initiate
ablation. Time-resolved shadowgraph images, coupled with etch-depth measurements
and temperature-rise calculations indicate that ablation begins after a superheated
surface layer reaches a temperature of ~1000 C and undergoes spinodal decomposition. The majority of the ablated material is then expelled by way of recoil-induced ejection as the pressure of the expanding vapor plume compresses a laser-melted area. For the first time, a consistent argument is presented to describe RIR polymer
ablation from beginning to end.
Applications of RIR ablation are also emonstrated through thin-film growth of
electronic and optoelectronic polymers. Conductive coatings of a commercially available thiophene polymer are made through a vapor-phase growth process, and polymer light-emitting diodes (PLEDs) are made by laser-transfer of a poly(phenylene vinylene) light-emitting polymer in vacuum. The functionality of the deposited films indicates that the RIR laser ablation process does not entirely decompose the con-
jugation of the polymers. The mechanisms derived from ablation studies on model polymer systems are used to explain various observations relating to film quality and device performance.
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