Laser photochemical

Deposition of Thin Films. Laser photochemical deposition has been extensively studied, especially with respect to fabrication of microelectronic stmctures (see Integrated circuits). This procedure could be used in integrated circuit fabrication for the direct generation of patterns. Laser-aided chemical vapor deposition, which can be used to deposit layers of semiconductors, metals, and insulators, could define the circuit features. The deposits can have dimensions in the micrometer regime and they can be produced in specific patterns. Laser chemical vapor deposition can use either of two approaches. 

Despite extensive studies, laser photochemical deposition has not yet replaced the conventional processes for fabrication of integrated circuits, except in selected appHcations such as making and breaking of selected links for customization of circuits and in the repair of defects. The reason is that laser processing of an entire wafer has remained more expensive than the conventional processes. 

Laser molecular beam epitaxy, fabrication method for inorganic materials, 7 415t Laser photochemical vapor deposition (LPCVD), 19114-116 Laser pointers, 14 678 Laser-promoted dehydrohalogenation,... 

D. L. Farrens and Pill-Soon Song, Subnanosecond single photon timing measurements using a pulsed diode-laser, Photochem. Photobiol. 54, 313-317 (1991). 

Lanthanide triflates, for allylic tin reactions, 9, 354 Laser beam heating, in metal vapor synthesis, 1, 224 Laser methods, in mechanistic studies, 1, 248 Laser photochemical vapor deposition, with organometallic complexes, 1, 259... 

Reversible processes. Distillation, chemical exchange. Irreversible processes require a continuous supply of work and use energy inefficiently. Among irreversible processes, electrolysis and laser-photochemical methods are important. 

Letokhov, V.S. On selective laser photochemical reactions by means of photopredissociation of molecules. Chem. Phys. Lett. 1972, 15, 221. 

Laser-induced reaction has been widely used to stimulate gas-surface interaction. Lasers are also used to probe molecular dynamics in heterogeneous systems as well. In the applied area, the laser photochemical techniques are successfully applied to produce well defined microstructures and new materials for microelectronic devices (1). Enhanced adsorption and chemical reaction on surfaces can be achieved by a photoexcitation of gaseous molecules, adsorbed species as well as solid substrates. The modes of the excitation include vibrational and electronic states of the gaseous species and of the adsorbates surface complexes. Both a single and a multiple photon absorption may be involved in the excitation process. 

Langmuir-Blodgett film transfer was used to prepare composites of GdS nanoparticles on Au substrates by Samokhvalov etal. [20]. Gharge transfer was observed using laser photochemical techniques. X-ray photoelectron spectroscopy (XPS) methods were used to study oxidation states. Photochemical studies... 

THE APPLICATION OF A DYE-LASER PHOTOCHEMICAL RELAXATION TECHNIQUE TO THE STUDY OF METAL-LIGAND SUBSTITUTION REACTIONS IN AQUEOUS AND MICELLAR SOLUTIONS... 

DYE LASER PHOTOCHEMICAL RELAXATION OF METAL-LIGAND REACTIONS... 

Fitzmaurice, D.J. and Frei, H., Photoinduced oxygen transfer from NOj to ethylene in the vicinity of the NOj dissociation threshold. A laser photochemical study on reactant pairs isolated in soHd... 

Using these characteristics of lasers, photochemical reactions that cannot be conducted with conventional Hght sources can be brought about, and a multiphoton reaction is one of these processes. Multiphoton reactions can be classified in two categories (1) stepwise reactions through short-lived transient species (Path 1 in Scheme 1) and (2) reactions by concerted multiphoton absorptions (Path 2 in Scheme 1). In many cases. Path 1 predominates when the substrates are complex organic compounds. The transient species can be either long-lived excited states, such as triplet states, or chemical species, such as radicals, carbenes, nitrenes, and thermally unstable molecules. 

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