Papers by Author: N. Guermat

Abstract: Humidity sensitive layers elaborated from pure HMDSO and TEOS by PECVD technique have been studied. Humidity sensing properties including impedance relative humidity (RH) and current RH characteristics were investigated. TEOS films show higher sensitivity and excellent linearity over the explored range of humidity (20–95% RH). However, HMDSO films exhibits a small response and recovery of about 8 and 34 s for humidification and desiccation, respectively, in addition to very low hysteresis (2%). Structural analyses of sensitive layers were characterized by Fourier transform infrared spectroscopy (FTIR).

Abstract: Humidity sensors are widely used in industry production, process control, environment monitoring, medical and electrical applications. In this study, water molecule sensitive layers have been elaborated by plasma enhanced chemical vapor deposition PECVD technique, from a mixture of hexamethyldisiloxane (HMDSO) and oxygen (O2) in different proportions. The films were deposited on a comb-shape aluminum electrode evaporated on glass substrate. Electrical and structural characteristics of the elaborated humidity sensors were evaluated by humidity-impedance characteristics, infrared spectroscopy FTIR and ellipsometric analysis. Electrical analysis showed that the elaborated humidity sensor exhibited a detectable response to relative humidity ranging from 35 to 95%. However, increasing O2 concentration in the mixture during deposition, leads to a significant decrease of the sensor sensibility. A sensor elaborated with pure vapor of HMDSO exhibited a better sensibility. FTIR analysis revealed that increasing O2 concentration induces a decrease of methyl groups CH3 and the formation of Si-O groups leading to film densification. Besides, the values of the refractive index deduced from ellipsometric data indicated that the refractive index increases with increasing the O2% in the mixture. This observation may be considered as further evidence to film densification.