Unexpected and enhanced electrostatic adsorption capacity of oxygen vacancy-rich cobalt-doped In2O3 for high-sensitive MEMS toluene sensor

Abstract

Benefiting from the enhanced electrostatic adsorption derived from surface oxygen vacancy, the reported MEMS based hollow-porous Co-In 2 O 3 gas sensor exhibits excellent selectivity and response, and toluene detection limits as low as 100 ppb at the lowest temperature so far. • The hollow-porous Co-doped In 2 O 3 microspheres with abundant electrostatic adsorption sites were synthesized by ultrasonic spray pyrolysis. • The MEMS toluene sensor reported in this work with the characteristic of low power consumption. • The Co-In 2 O 3 gas sensor exhibits high sensitivity and superior selectivity to ppb level of toluene at relatively lower temperature. • Demonstrating the impact of electrostatic adsorption on charge carrier transport and toluene sensing performance by DFT calculation. Semiconductor metal oxide (SMO) gas sensor has been widely researched in artificial olfactory for monitoring gases and odor. However, realizing the characteristics of low detection limit, immunity from interference capacity and low operating temperature still remains challenge. Herein, the synthesis of hollow-porous cobalt-doped In 2 O 3 sensing material with abundant surface oxygen vacancy (SOV) via one-pot and in-situ doping approach is reported. With their rich active sites, the Co-In 2 O 3 exhibits unexpected and high electrostatic adsorption of toluene at 175 °C, which obviously inducing the charge carrier transport. Accordingly, the final Microelectro Mechanical Systems (MEMS) based Co-In 2 O 3 gas sensor exhibits excellent selectivity and response, and toluene detection limits as low as 100 ppb at the lowest temperature so far. Density functional theory (DFT) calculations elucidated that the enhanced electrostatic adsorption is ascribed to the toluene preferentially bound to O 3c atom site (bridging oxygen atom near SOV) on Co-In_b-D 4 (110) surface, which will induce charge carrier accumulation layer and cause temperature-dependent abnormal pseudo p-type response. This work points out that the electrostatic adsorption derived from SOV could obviously modulate SMO sensing properties, and further supplements the defect engineering.