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 polymers laser infrared laser ablation pulsed-laser deposition polymer thin-films
Date of Defense	2008-08-07
Availability	unrestricted
Abstract Resonant 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.
Files	Filename       Size       Approximate Download Time (Hours:Minutes:Seconds)     28.8 Modem   56K Modem   ISDN (64 Kb)   ISDN (128 Kb)   Higher-speed Access    Thesis_final.pdf 4.37 Mb 00:20:12 00:10:23 00:09:05 00:04:32 00:00:23