Capacitive humidity sensor based on amorphous carbon film/n-Si heterojunctions

Amorphous carbon (a-C) films were deposited on n-silicon by direct current magnetron sputtering at room temperature (RI) and the corresponding microstructures were characterized The RT capacitive humidity sensing properties of the a-C film/n-Si (C/Si) heteroonctions were studied by a standard two-probe method The result shows that the capacitance of the heterojunct ions increases with decreasing frequency. because the adsorbed water molecules can become mole polarized at lower frequencies. It was also shown that with the relative humidity (RH) changing from 11% to 95%, a capacitive response of over 200% was achieved at 1 kHz. and the capacitive response is highly linear with RH for the given frequencies. The increase in capacitance of the C/Si Junction with increasing relative humidity can be attributed to the increase in the amount of physisorbed water having a dipole moment The study shows that the C/Si junctions have potential application as humidity gas sensors. (C) 2010 Elsevier B.V. All rights reserved