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Title page for ETD etd-08082008-140048

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
  • laser ablation
  • polymers
  • laser
  • infrared laser ablation
  • pulsed-laser deposition
  • polymer thin-films
Date of Defense 2008-08-07
Availability unrestricted
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.

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