Study On The Gas Sensors Based On Porous Silicon And Tungsten Oxide Nano Hierarchical Structure Composites

Nitrogen dioxide plays a major role in the formation of acid rain,ozone,and photochemical pollution even at very low concentrations,which is harmful to human health.Therefore,the development of high sensitivity,excellent response-recovery performance of the NO₂ gas sensor is of great significance.The WO₃ hierarchical structures can provide more active surface and interface,which is beneficial to carrier transport,so as to improve the gas-sensing performance.Porous silicon has been extensively studied for its gas-sensing properties at RT and being easily compatible with integrated circuits.Therefore,the preparation technology of WO₃ hierarchical composite with PS was studied,as well as the gas-sensing properties and mechanism.The thorn-sphere-like WO₃ made up by 1D nanorods has been synthesized through hydrothermal method on the Au-modified PS substrates with seed-layer induction.The results of XRD,EDS,FESEM and TEM showed that the crystal structure and morphological evolution of WO₃ on Au-modified PS are dependent on the Au-sputtering time and hydrothermal reaction time.The samples with the best morphology exhibited high sensitivity and excellent response to ppb-level NO₂ at RT.WO₃ hollow nanospheres prepared by template method were spin-coated on the PS surface to form the PS/WO₃ composite gas sensor.Aging time has a great influence on the formation of WO₃ hollow nanospheres.The sensitivity of the synthesized PS/WO₃ hollow nanospheres composite gas sensors to 1 ppm NO₂ is 12,with good selectivity and response-recovery characteristic.The hydrothermal method was used to prepare WO₃ nanorods/graphene composites,the composites formed by the spin-coating method combined with PS had excellent response to NO₂ gas at RT.It was found that the pH value of the hydrothermal solution affected the morphology of WO₃/graphene composites and the optimum preparation was obtained through comparing the preparation parameters.In this study,the preparation techniques and the gas-sensing response mechanisms of the above three topics were studied in the paper,which laid a foundation for the study of hierarchical structure and heterostructure gas sensor.