ZnO and AlZnOx freestanding cantilevers toward the detection of volatile organic compounds with high selectivity and sensitivity

Abstract Nanoscale, self-actuating cantilevers are promising low-power gas sensors, but the development of different cantilever materials with optimized designs is needed to improve performance and reliability. Here we show the fabrication of cantilevers from nanoscale zinc oxide and aluminum zinc oxide thin films. Atmospheric-pressure spatial atomic layer deposition is used to deposit the oxide layers, and the microfabrication process is revised to overcome cantilever stiction, oxide cracking, and top-electrode damage during reactive ion etching. Optimizing the top electrode thickness mitigates unwanted cantilever bending and enhances the quality factor fivefold. The zinc oxide cantilever demonstrates high sensitivity to humidity (22,261 ppm/%RH) making it ideal for precise moisture detection, while the aluminum zinc oxide cantilever exhibits selectivity toward volatile organic compounds (maximum 0.1621 Hz/ppm to ethanol), with a much lower sensitivity to humidity (2,892 ppm/%RH). This suggests that humidity interference can be mitigated by fabricating arrays with both types of cantilever. Their distinct response patterns would enable selective identification of volatile organic compounds while rejecting interference from humidity.