Thin film technology laser ablation

Preparation of catalyst libraries for the discovery phase can be broadly divided into two categories (1) solution-based methods, and (2) thin-film deposition/based methods. The solution-based methods include those that utilize (1) multi-tasking robotic workstations [14-16] (2) inkjet printhead technology [17], and (3) microjet technology [18]. The thin-film deposition-based methods employ electron beam and thermal evtqroration, sputtering, pulsed laser ablation, and chemical vapor deposition (see [60] in [13] for a list of references). A detailed discussion of how these have been applied is provided elsewhere [13]. Web sites provide links to various aspects of combinatorial chemistry (www.combichem.net and www.5z.com). Here, the hardware aspects are lightly sketched. 

New developments relating to the manufacture of thin film transistors (TFT) are being reported from Japan where the Tokyo Institute of Technology has developed a flexible, transparent device on a PETP substrate. This TFT comprises an amorphous oxide semiconductor, which serves as the active layer, and which is made from indium, gallium and zinc oxide deposited by laser ablation to a thickness of 30-60 nm. The TFT, with its transparent electrodes and circuitry, is manufactured in a vacuum at a temperature of 150 "C or less. Because of this low processing temperature it is possible to use low cost PET film, with a thickness of 200 pm, as a substrate thereby enabling transistors to be manufactured at a relatively low cost. 

A. Morimoto, T. Shimizu, Laser ablation, in D.A. Glocker, S. Ismat Shah (Eds.) Handbook of Thin Film Process Technology, vol. 1, Taylor Francis, 2002, Sec A1.5. 

Chan et al. (2005), have realised micro fuel cells through an approach that combines thin film materials with MEMS (micro-electro-mechanical system) technology. The membrane electrode assembly was embedded in a polymeric substrate (PMMA) which was micromachined through laser ablation to form gas flow channels. The micro gas channels were sputtered with gold to serve as current collectors. This cell utilized the water generated by the reaction for the humidification of dry reactants (H2 and O2). The peak power density achieved was 315 mW cm (901 mA cm" at 0.35 V) for the H2-O2 system with 20 ml min" O2 supply and H2 at 10 psi in dead ended mode of operation. A Y shaped microfluidic channel is depicted in Fig. 21. 

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