Ammonia (NH3) sensors based on carbon/silicon (C/Si) heterojunctions are demonstrated at room temperature (RT). Upon exposure to NH3 molecules (0.2 ml l−1) at RT, the interface capacitance of C/Si junction increases dramatically, to about 230%. The results show that C/Si junctions have high NH3 gas sensitivity, rapid response and high recovery speed at RT. This phenomenon can be attributed to the change of the potential barrier width of the junction, which is caused by the adsorption of NH3 gas molecules. The C/Si junctions can greatly amplify the detection sensitivity of the nano-sized carbon so that the C/Si junctions act as excellent RT gas sensors.
