SUPPRESSION OF GRAIN-GROWTH IN SOL-GEL-DERIVED TIN DIOXIDE ULTRATHIN FILMS

Tin dioxide thin films of various thicknesses up to 150 nm were prepar ed on quartz glass substrates from a sol solution of SnO2 (particle si ze 3 nm) by a spin-coating method and subjected to calcination at diff erent temperatures up to 800 degrees C for 30 min, The grain size of S nO2 was found to be far smaller than those obtained from the SnO2 sol- derived powder under the same calcination conditions, The suppression of grain growth of SnO2 was more conspicuous as the film thickness dec reased so that in the thinnest film (20 nm thick) the SnO2 grain size remained as small as 6 nm after calcination at 800 degrees C, It is su ggested that the SnO2 grains in the ultrathin film deposited on the su bstrate are restrained from moving and coalescing with each other, res ulting in the suppression of grain growth.