Electrochemical synthesis and the gas-sensing properties of the Cu2O nanofilms/porous silicon hybrid structure

A novel composite of Cu2O nanofilms/porous silicon hybrid structure has been successfully synthesized using porous silicon as growth substrate by electrochemical synthesis. Orderly porous silicon (PS) substrate with the aperture about 1.5 μm and hole depth about 10 μm was prepared by electrochemical etching of a p-type monocrystalline silicon wafer in a double-tank cell. The Cu2O nanofilms have been grown onto PS substrates by electrochemical deposition with different electrodeposition time. The obtained Cu2O nanofilms/PS products were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscope (TEM). The gas-sensing properties of Cu2O nanofilms/PS composites to NO2 were studied by the gas-sensing test system. The result indicates that the electrodeposition time has a significant impact on the microstructure and gas-sensing properties of Cu2O nanofilms/PS composites. Due to the high specific surface area and special microstructure, the Cu2O nanofilms/PS gas sensor with the eletrodeposition time of 30 min showed good gas-sensing properties to NO2 with a high gas response, fast response-recovery characteristic, excellent repeatability and good selectivity at a working temperature of 175 °C. At the working temperature, the gas sensor has a gas response of about 4.5-1 ppm NO2. The related gas-sensing mechanism will be discussed.