Effect of Bi doping on structural, morphological, optical and ethanol vapor response properties of SnO2 nanoparticles

The gas sensing behavior of thick films of Bi doped SnO2 has been investigated towards ethanol vapor. The screen printing technique was used to prepare the thick films. The films were sintered at 650 °C for 2 h. The structural, surface morphological, optical and gas sensing properties of undoped and Bi doped SnO2 thick films have been studied. X-ray diffraction and Raman spectroscopy confirmed that the films consisted exclusively of tetragonal tin oxide, without any impurity phases. FE-SEM studies revealed the formation of highly porous microstructure with grain size in few tens of nanometers. From the optical studies, the band gap was found to be decreased with bismuth doping (3.96 eV for undoped, 3.83 eV, 3.71 eV and 3.6 eV for 1 mol%, 2 mol% and 3 mol% Bi, respectively). The 3 mol % Bi doped SnO2 thick films exhibited the highest sensitivity to 100 ppm of ethanol vapor at 300 °C. The effect of microstructure on sensitivity, response time and recovery time of the sensor was studied and discussed.