DEPOSITION OF TRANSPARENT CONDUCTIVITY OF FLUORINE-DOPED SnO2 THIN FILMS BY SPRAY PYROLYSIS METHOD
SnO2 and SnO2:F thin films were successfully deposited on a glass wafer substrate by spray pyrolysis method using SnCl2.5H2O and NH4F as precursors. The effect of deposition temperature and fluorine concentration on the crystal phase formation of SnO2 was investigated by XRD. The results showed that the films were crystallized in the form of SnO2 with a tetragonal structure at deposition temperature above 400 oC. No XRD peaks related to SnO2 were found on the films that deposited at a temperature lower than 350 oC. The sheet resistance of the SnO2 films was increased with the increase in the deposition temperature. The crystalline structure of the SnO2 films did not change in the presence of fluorine impurities while their sheet resistance was significantly decreased. The minimum sheet resistance was 3.7 (Ω\□) corresponding to the samples deposited with the fluorine concentration of 20 wt%. SEM images also showed the crystal shape of SnO2 in which crystal size decreases with an increase in fluorine concentration. Both SnO2 and SnO2:F exhibited good transparent properties in visible light. The bandgap of the SnO2 films was about 3.90 eV and was slightly expanded when the concentration of fluorine was increased.