TIN DIOXIDE-BASED TRANSPARENT SEMICONDUCTING-FILMS DEPOSITED BY THE DIP-COATING TECHNIQUE

Undoped and F-doped transparent semiconducting films with tin dioxide as the active material have been prepared by a dipcoating technique. T he film is formed in situ by the hydrolysis of stannous chloride which takes place when a substrate is withdrawn vertically from a methanol solution of SnCl2.2H(2)O and heat treated at a high temperature. F-dop ing is achieved by adding NH4F to the starting solution. The maximum f ilm thickness obtainable per dipping cycle is about 0.58 mu m, but can be increased by multiple dipping. The films appear to be a mixed phas e consisting of crystalline tin oxide over an amorphous background, pr obably of Sn (OH)CI. The him produced by a single dipping consists of a small number of isolated SnO2 crystallites. But as the film thicknes s is increased these crystallites increase in number and finally merge into a continuous layer. A typical value of resistivity for F-doped f ilms produced by this method is 2.4 x 10(-2) Omega cm. with an average transmission of similar to 85% at a thickness of 2.96 mu m. (C) 1998 Elsevier Science S.A.