Conclusions
We have fabricated cerium oxide thin films using electron-beam evaporation and subsequently annealing them at 500 ◦C. The films were found to be amorphous and highly porous. The films were investigated for application as CO gas sensors. They were found to be highly sensitive to CO, and their response magnitude strongly depends on bias voltage, gas concentration, and operating temperature. The lower detection limit was 500 ppm, and the optimum operating temperature was around 390 ◦C. The senor responded in 45 s and recovered back in 25 s.