LASER FIRING OF TRANSPARENT CONDUCTING SNO2 SOL-GEL COATINGS

Sb doped sol-gel SnO2 films were prepared from 0.5 M alcoholic solutio n of SnCl2(OAc)(2) doped with 5 mol% SbCl3 and deposited via a dip coa ting process on fused silica substrates. The coatings have been fired by CO2 laser irradiation by means of a 700 W cw CO2 laser using a fast scan mode in which the laser beam is scanned by a high speed rotating polygon scanner (omega(max) = 8800 rpm) in one direction and the samp le is moved perpendicularly at a speed up to 250 mm/s. Areas can be de nsified at a typical rate of approximate to 12 cm(2)/s. The properties of the coatings have been measured by several methods: their sheet re sistance, R-square has been measured using a four-probe technique, the structure of the coatings has been determined by X-ray diffraction at grazing incidence, their thickness by a surface profiler and their mo rphology by transmission electron microscopy. The thickness of the coa tings, the crystallite size and the sheet resistance are determined by thermal driven processes. The coatings are made of dense aggregates o f spherical shaped crystallites. The smallest resistivity obtained for a 100 nm thick coating is rho = 6 x 10(-3) Omega cm a value that is t hree times lower than that obtained with conventionally heat treated s amples. (C) 1997 Elsevier Science B.V.