Impedance characteristics of carbon nitride films for humidity sensors

Carbon nitride films were deposited on silicon substrate for humidity sensors with meshed electrodes by reactive RF magnetron sputtering system with DC bias. The surface of carbon nitride films had a good uniformity with the grain size of about 30 nm. The EDS analysis revealed that the chemical formula of the carbon nitride film is C₂N when it was deposited with 50% N₂ ratio for 1 hr. The impedance of the sample having the total sensing area of 1.00 mm² gradually decreased from 120 kΩ to 2 kΩ in the relative humidity range of 5% to 95%. Hysteresis was about 4.2% of full scale. As the film thickness increased, impedance change ranges and each impedance values also increased. As far as the results are concerned, carbon nitride films have a several advantages for a new humidity sensing material.