A Chemical Method for Deposition of Thin Film of

Thin film formation of chalcogenides of Pb 2+ by chemical deposition is a very well known process (1,2,3). But similar methods of deposition of thin films of Bismuth chalcoge-aides have not yet been reported. This brief communication describes a chemical method for the deposition of Bi2S 3 thin films. 10-30 x 106 ohm-cm. The temperature variation of resistivity shows that activation energy of electrical conduction is 1.3 eV. The material has n-type conduction. The optical band gap of the film is found to be 1.&7 eV shown in the figure (2) and it has feeble photo conductivity. Thio-urea is used for slow release of S 2- ion and pH is maintained at 8. To keep Bi3+ ion in solution at pH 8, triethanolamine complex of Bi3+ is used. One gm of bismuth nitrate (Bi(NO~)~,SH20) is triturated with i0 ml triathanolam~n'e and then 50 ml water is added to it. The resulting solution is continuously stirred till a nearly clear solution is obtained, which is then filtered. A 20 ml of the Bi 3+ solution is taken in a glass beaker. 30 ml ofl(M~hiourea solution and 1 ml of 17 (N) NHhOH are added to it and the volume is made upto lOO ml with water. The substrate (glass or ceramic) is thoroughly cleaned and immersed in the solution. The container is placed into an oil bath at lOO-llO ~ temperature for AOminutes and then it is kept at room temperature for about A hours. Uniform films of Bi2S 3 are obtained on the glass substrates. They are then taken out, washed with water and dried in air. The Bi2S 3 films are about 0.05- O.1 microns thick. NHhOH is added to slow down the formation c. ~ Bi2S 3 and to increase its adherence on the glass substrate