A capacitive humidity sensor based on ordered macroporous silicon with thin film surface coating

In this paper, we report a new approach for humidity sensing. The sensor is based on ordered macroporous silicon with a Ta2O5 thin film coating. The ordered macroporous silicon array has perfectly aligned pores and uniform pore size (4 μm). The 95 nm Ta2O5 thin film is uniformly deposited on the pore surface by atomic layer deposition (ALD), which acts as an adsorption enhancement layer. The sensor's capacitance is measured to RH changes. The sensor shows very high sensitivity and small hysteresis, especially at high RH levels. It also shows very good repeatability and long term stability.