Influence of the heating rate on the microstructure and on macroscopic properties of sol-gel SnO2:Sb coatings

Sol-gel dip-coated films of transparent conducting antimony-doped tin oxide (SnO2:Sb) have been heat treated with heating rates varying from 0.2 to 4300 Ws using either a furnace or cw CO2 laser irradiation. The final sintering temperature of 540 degrees C was maintained for up to 15 min. The sheet resistance of the coatings decreases with increasing heating rate. A decrease of the sheet resistance with the sintering time at constant temperature can be observed for low heating rates but the final values are higher than those obtained with higher heating rates. It is assumed that the densification of the coatings is determined by a competition between the nucleation at low temperatures and the growth of the crystallites at high temperatures. The microstructure of the coatings has been investigated by high resolution TEM cross-sections, X-ray diffraction, and Rutherford back scattering (RBS) and has been correlated to the resulting electrical properties measured by 4 point technique. Different mechanisms of heating arise with the furnace and the cw CO2 laser.