In this work, we have elaborated and characterized polyaniline (PANI) thin films doped with sulfuric acid (H2SO4) using cyclic voltammetry (CV). The PANI has been electrodeposited onto hydrogenated amorphous silicon carbide (a-SiC:H) films, obtained by DC magnetron sputtering. The structural properties of PANI/Au/a-SiC:H hetero-structure were investigated by the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The electrochemical properties of PANI-based films were studied by the current (and/or capacity) voltage (I-V and C-V) characteristics and electrochemical impedance spectroscopy (EIS). The elaborated hetero-structure has been used for ammonia (NH3) vapor detection. The results showed that the synthesized PANI-H2SO4 thin film exhibited a nanofibrous texture with a good sensitivity to NH3 vapor. The response and recovery times were 14 and 6 s, respectively, and seem to be a good achievement for the detection of low NH3 concentrations.