The grafting of organic molecules onto semiconducting substrates modifies their surface properties and can be used toprepare materials with potential applications such as capacitors, sensors, anti-corrosive coatings, batteries and actuator.The present work reports the electrochemical grafting of polyaniline doped with sulfuric acid (H2SO4), onto a thinhydrogenated amorphous silicon carbide (a-SiC:H) films, via cyclic voltammetry method. The confirmation of PANI was doneby FT-IR which displayed the principal characteristic peaks attributed to the different functional groups. Scanning electronmicroscopy (SEM) was used to evaluate the surface modification. The electrochemical properties of PANI samples were studiedby CV and electrochemical impedance spectroscopy tests. The structure has been tested for ammoniac (NH3) vapor detection.