Ethanol gas sensing performance of electrochemically anodized freestanding porous SiC

The thick layers of freestanding porous silicon carbide (PSiC) were synthesized by electrochemical etching of polycrystalline silicon carbide (3C-SiC) substrates. The obtained layers exhibit homogenous nanostructured morphology with average pore diameter of 9–14 nm, the surface area of 87 m2/g and the pore volume of 0.30 cm3/g. The visible photoluminescence peaks with maxima at 2.00; 2.71; 3.25 eV are related to defect surface centers and nanocrystals introduced by HF reaction with SiC. Raman's observations confirm that the PSiC structure maintains its crystallinity after dissolution process. The applicability of electrochemically formed freestanding PSiC for gas sensing was verified by impedance spectroscopy. The hodographs of total impedance and influence of ethanol adsorption/desorption on their shape were examined. The behavior of complex resistivity at adsorption/desorption of ethanol is interpreted in terms of the electronic states recharge on SiC surface.