Magnetron co-sputtering optimized aluminum-doped zinc oxide (AZO) film for high-response formaldehyde sensing

Highlights: • The aluminum-doped zinc oxide (AZO) film was prepared by magnetron co-sputtering technology. • Four AZO thin films formaldehyde sensor samples with different Al content were prepared. • The optimal operating temperature of the sensor was 240 °C. • The sensor can detect formaldehyde as low as 50 ppb. • The sensor shows excellent long-term stability and selectivity. -- Abstract: It is very important to conduct trace detection of the gas formaldehyde, a harmful gas of volatile organic compounds (VOCs) that threatens human health. In the present work, the aluminum-doped zinc oxide (AZO) films with different aluminum contents were prepared on silicon substrate by magnetron co-sputtering technology. The test results showed that when the sputtering power of ZnO was 150 W and the sputtering power of Al₂O₃ was 50 W, the AZO thin film sensor had the best response to formaldehyde at an operating temperature of 240 °C. The sensor had a good response to 100 ppb-3 ppm formaldehyde, and its response to 100 ppb formaldehyde at 240 °C was as high as 43%. The sensor could detect as low as 50 ppb to formaldehyde, and it also exhibited good repeatability, long-term stability, as well as good selectivity over other gases (hydrogen, carbon monoxide, ammonia, benzene, isoprene, nitrogen dioxide and acetone). Therefore, this AZO thin-film sensor is expected to be used in indoor formaldehyde monitoring.