Temperature programmed desorption of F-doped SnO2 films deposited by inverted pyrosol technique

Fluorine-doped tin dioxide (FTO) films were deposited on silicon wafers by inverted pyrosol technique using solutions with different doping concentration (F/Sn=0.0,0.1,0.75 and 2.50). The physical and electrical properties of the deposited films were analyzed by SEM, XRF, resistivity measurement by four-point-probe method and Hall coefficient measurement by van der Pauw method. The electrical properties showed that the FTO film deposited using the solution with F/Sn=0.75 gave a lowest resistivity of 3.2*10 ohm cm. The FTO films were analyzed by temperature programmed desorption (TPD). Evolved gases from the heated specimens were detected using a quadruple mass analyzer for mass fragments m/z, 1(H), 2(H2 ), 12(C), 14(N), 15(CH3 ), 16(O), 17(OH or NH3 ), 18(H2O or NH4 ), 19(F), 20(HF), 28(CO or N2 ), 32(O2 ), 37(NH4F), 44(CO2 ), 120(Sn), 136(SnO) and 152(SnO2 ). The majority of evolved gases from all FTO films were water vapor, carbon monoxide and carbon dioxide. Fluorine (m/z 19) was detected only in doped films and its intensity was very strong for highly-doped films at temperature above 400 deg C.