Principal Component Analysis-Assisted Detection of Toxic Chemicals Using Atomic Layer Deposition-Grown Zinc Oxide Thin Films

In this study, a highly sensitive and selective gas sensor was developed for detecting hazardous analytes, including ethanol, acetone, hydrogen sulfide (H2S), and hydrogen cyanide (HCN). ZnO thin films were deposited as the sensing layer using atomic layer deposition (ALD), while Au interdigitated electrodes with 5 µm width and spacing were fabricated on SiO2/Si substrates via photolithography. The fabricated sensor exhibited a sensitive response to the target gases even at part-per-billion (ppb). However, it was observed that as the operating temperature decreases, the sensor signal's noise level increases. Additionally, the recovery time for the sensor to return to its baseline value after gas exposure was significantly affected by the operating temperature. The detection limits for ethanol, acetone, H2S, and HCN were 14.6, 35, 115, and 115 ppb, respectively, confirming the sensor's ability to detect all analytes at concentrations well below their threshold limit values. Principal Component Analysis (PCA) revealed well-separated clusters for each analyte, particularly for ethanol and acetone, suggesting that the sensor can effectively discriminate between these two gases. These results demonstrate the sensor’s excellent sensitivity and selectivity supporting its potential for real-time monitoring of toxic gases in environmental and industrial applications.