Preparation And Gas Sensing Properties Research Of Porous Silicon Based Metal Oxide Nanocomposites

As a kind of new micro-nano structure material, porous silicon (PS) has greatapplication potential in the field of gas sensors due to their special microstructure. Inthis paper, PS, ZnO nanostructures/PS and Cu2O nanofilms/PS were prepared andtheir gas sensing properties were studied.Orderly PS layer with the aperture about1.5microns was prepared byelectrochemical etching of a p-type monocrystalline silicon wafer with the resistivity10-15cmand <100> orientation in a double-tank cell. The results show that theetching time has a significant impact on the microstructure and gas sensing propertiesof PS. When the etching was over a certain time, the aperture of PS was saturated andthe etching proceeded to the depth. The gas sensing test results indicate that the PSshows a better gas-sensing property to NH3than that to NO2. The gas sensitivityincreases with the increasing of porosity and the response/recovery time increaseswith the increasing of the hole depth. The PS with a suitable etching time shows goodgas sensing properties to NH3with high sensitivity, fast response-recoverycharacteristic and excellent selectivity.ZnO nanostructures such as nanosheets and nanorods were successfullydeposited onto the PS substrate by electrochemical deposition. The microstructure andgas sensing properties of the ZnO nanostructures/PS composite were studied. The gassensing tests show that the working temperature of ZnO nanostructures/PS gassensors is room temperature. Due to the high specific surface area and specialmicrostructure, ZnO nanosheets/PS gas sensor shows good gas sensing properties toNO2with high sensitivity, fast response-recovery characteristic, excellent stability andselectivity. At room temperature, the gas sensor has a sensitivity of about5.8to1ppmNO2.Cu2O nanofilms were successfully deposited onto the PS substrate by electrochemical deposition. The microstructure and gas sensing properties of theCu2O nanofilms/PS composite were studied. The gas sensing tests show that theworking temperature of Cu2O nanofilms/PS gas sensors is about175℃. Due to thehigh specific surface area and special microstructure, the Cu2O nanofilms/PS gassensor with a suitable eletrodeposition time showed good gas sensing properties toNO2with high sensitivity, fast response-recovery characteristic, excellent stability andselectivity. At the working temperature, the gas sensor has a sensitivity of about4.5to1ppm NO2.