SAW Temperature and Humidity Assembled Sensor Based on AlScN Piezoelectric Thin Film

Abstract

This article proposes a temperature-humidity assembled sensor based on AlScN surface acoustic wave (SAW) technology for simultaneous monitoring of temperature and humidity. The assembled sensor includes two SAW resonators with frequencies of 475 and 493.675 MHz. The AlScN thin film serves as the piezoelectric film for the temperature and humidity sensor. Graphene oxide (GO) is used as the humidity-sensitive film in the sensor. The humidity sensor can detect a frequency shift of 587.5 kHz within the range of 20%–90% RH, with sensitivities of 4.75 kHz/%RH at low humidity (20%–50% RH), 9.33 kHz/%RH at medium humidity (50%–80% RH), and 16.3 kHz/%RH at high humidity levels (80%–90% RH). The assembled sensor demonstrates excellent stability and repeatability, with a response time and recovery time of 8.5 and 6 s, respectively. The temperature and humidity sensors have a similar temperature coefficient of frequency (TCF). The sensor measures ambient temperature using the temperature sensor and employs a decoupling algorithm to mitigate the impact of temperature on the humidity sensor, improving its accuracy.