Humidity sensing properties of carbon nanowall films synthesized by CCP-PECVD

Abstract

Carbon nanowall (CNW) films were synthesized by capacitively coupled plasma-enhanced chemical vapor deposition and evaluated as active layers for resistive humidity sensing. SEM observations confirmed the formation of vertically oriented CNW sheets, while Raman analysis showed typical defect-related and graphitic carbon bands, confirming the formation of a petal-like carbon nanowall network. Humidity-sensing performance was studied over a relative humidity range of 10–100% at 27, 50, and 75 °C. The fabricated sensors exhibited repeatable electrical responses over short cycling tests and a clear temperature dependence. At 27 °C, the sensor showed the highest sensitivity, reaching 2.27% at 100% RH, with response and recovery times of 87 and 97 s, respectively. Increasing the operating temperature reduced the sensitivity to 0.49% at 50 °C and 0.22% at 75 °C, which can be attributed to enhanced desorption of water molecules from the CNW surface. These findings indicate that transferred CNW films can be considered as simple and inexpensive platforms for humidity monitoring.