Al-Assisted Photochemical Etching of a-SiC Thin Films for NH3 Sensor
A. Boukezzata, H. Menari, S. Kaci
Centre de Recherche en Technologie des Semi-conducteurs pour l'Energétique (CRTSE), Division Couches Minces Surfaces et Interfaces (CMSI), Algiers, Algeria
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In this work, we present the formation of porous amorphous silicon carbide (PASiC) fabricated on a thin amorphous silicon carbide (a-SiC) film. The film was deposited on p-type silicon substrate (a-SiC/Si(p)) by co-sputtering DC magnetron using a single crystal Si target rand deposited onto 86 sprigs of hot pressed polycrystalline 6H-SiC. The thickness of the elaborated a-SiC films was 0.2 μm. Due to its high electrical resistivity of a-SiC:H thin film (higher than 2 MΩ cm), and in order to facilitate the chemical etching, a thin metallic film of high purity aluminum (Al), was deposited under vacuum. The PASiC films were made by Al-assisted photochemical etching using HF/AgNO3 solution under UV illumination at λ=254 nm with different etching times. The results show that the sample surface is uniformly covered with pores. The diameter of pores varied between 150 and 700 nm. The optimum etching time corresponded to 30 s that exhibited a high PL intensity. The NH3 sensors were fabricated by evaporating coplanar interdigital gold (Au) electrodes on PASiC and the vapor sensing properties were tested. Finally, the sensing performances are attributed to the unique surface structure, morphology of the pore and its size, which provide an effective pathway for vapor adsorption and enlarge the sensing area of Au-PASiC.

topics: amorphous silicon carbide, porous SiC, metal-assisted, photochemical etching