Polymer films pulsed laser deposition

The pulsed laser deposition (PLD) technique is widely used for inorganic materials but is beconting increasingly employed for the preparation of thin films of polymers... 

J. Talton, G. Hochhaus, J. Fitz-Gerald, and R. Singh. Pulsed laser deposited polymer films onto pulmonary dry powders for improved drug delivery. MRS 1998 Fall Meeting, Boston, 1998, p. 597. 

During the last decade, processing of polymers has become an important field of applied and fundamental research [48]. One of the most important fields is laser ablation involving various techniques and applications. Laser ablation is used as an analytical tool for MALDI (matrix-assisted laser de-sorption/ionization) [28, 29] and LIBS (laser-induced breakdown spectroscopy) [49] or as a preparative tool for PLD (pulsed laser deposition) of inorganic materials [37] and of synthetic polymer films [50, 51]. Another application is surface modification of polymers [52] if low fluences are applied, the polymer surface can be either chemically modified to improve adhesion... 

Since its discovery, laser polymer processing has become an important field of applied and fundamental research. The research can be separated into two fields, the investigation of the ablation mechanism and its modeling and the application of laser ablation to produce novel materials. Laser ablation is used as an analytical tool in matrix-assisted laser desorption/ionization (MALDI) [12,13] and laser-induced breakdown spectroscopy (LIBS) [14] or as preparative tool for pulsed laser deposition (PLD) of synthetic polymers [15,16] and of inorganic films [17,18],... 

Phillips HM, Li Y, Bi X, Zhang B (1996) Reactive pulsed laser deposition and laser induced crystallization of SnO transparent conducting thin films. Appl Phys A 63 347-351 Pique A, Auyeung RCY, Stepnowsk JL, Weir DW, Arnold CB, McGiU RA, Chrisey DB (2003) Laser processing of polymer thin films for chemical sensor applications. Surf Coat Technol 163-164 293-299 Randhaw H (1991) Review of plasma-assisted deposition processes. Thin Solid Films 196 329-349 Risti M, Ivanda M, Popovi S, Musi S (2002) Dependence of nanocrystaUine SnO particle size on synthesis route. J Non-Crystal Solids 303 270-280... 

Examples for the second group are polymers as fuel in the micro laser plasma thruster (JJ.LPT), PLD of polymers, matrix-assisted pulsed laser evaporation (MAPLE), which is a deposition technique that can be used to deposit highly uniform thin films [26], or laser-induced forward transfer (LIFT) [27-29], which can be used to produce microstructures by transferring an irradiated area of a target film to an acceptor substrate. The polymer can be the transferred material, or just functions as driving force in the transfer. 

While the growth of conductive polymer layers onto bulk high-Tc ceramic pellets can be accomplished readily, the use of thin films of YBa2Cu307- s is preferred for the construction of polymer/superconductor bilayer structures. Consequently, thin films of YBa2Cu707 is (—200-5(X)0 A in thickness) were deposited onto singlecrystal MgO(KX)) substrates using the pulsed laser ablation method [291, and these films were used to create polymer/superconductor bilayer structures. The result-... 

Figure 10-12. Lcfi hand side Slruclure of a PPV microcavily. A thin film of ihe conjugated polymer is deposited on top of a highly reflective distributed Bragg refieclor (DBR). The second mirror is then fabricated by evaporation of a silver layer. Right hand side Emission spectra of the microcavily at excitation cnetgics or 0.0S pJ (dashed line) and l. l pJ (solid line), respectively. Laser pulses ol duration 200-300 ps and a wavelength of 355 nm were used for optical excitation (according to Ref. [39]).

Principles and Characteristics Laser ablation is conceptually very simple, but mechanistically complicated. The process involves coupling of the photon energy of a laser pulse (typically about 20-30 ns wide, with an energy of 1-10 Jcm ) into the surface of a solid, resulting in evaporation and ejection of various species from the surface (the so-called plume ) within 10 to 10 s. The first experiments were carried out in 1962 [32]. When focused to a small area, a laser beam provides enormous power densities and electromagnetic fields. The plume , presumably a plasma, is accompanied by shock waves and electrical breakdown. The ejected material may eventually be deposited as a thin film. It is possible, by suitable selection of laser power and focus, to ablate a range of plastic materials in a controlled manner. For some matrices the polymer melts and diffuses away from the centre of the ablation site, leading to the forma-... 

Studies have shown that adhesion of metals to PTFE improved when it was irradiated by x-ray or electron beam prior to deposition. ] Evaporated nickel adhered better to the x-ray irradiated PTFE surface than the unaffected surface. The increased adhesion was attributed to the possible formation ofNi-C bonds to bind the nickel to the polymer chain. Another studyb24] reported enhanced adhesion of copper films on polytetrafluoroethylene that had been irradiated with a pulsed ultraviolet excimer laser prior to deposition. 

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