TPD and ITPD study of materials used as chemoresistive gas sensors

Temperature-programmed desorption (TPD) and a differential form of it, called intermittent temperature-programmed desorption (ITPD), turned out to be powerful characterising techniques for chemoresistive materials applied to gas sensing. We investigated samples of SnO2, TiO2 and solid solutions of them (TixSn1 − xO2). TPD and ITPD experiments were carried out in vacuum, with samples previously treated in pure O2 (100 Torr, 500 °C, 30 min). Amounts of desorbed O2 corresponded for all Ti-containing samples to less than 10% of a compact monolayer of ions O2−. Corresponding values of the apparent activation energy of desorption (Eapp) were calculated directly from the Arrhenius plots for each partial TPD and ranged from about 100 to 330 kJ mol− 1 (1.16 to 3.82 eV).