Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersi...Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersive spectroscopy（EDS）, and x-ray diffraction（XRD）. The NO_2-sensing performances in terms of sensor response, response/recovery times and repeatability at room temperature were optimized by varying the heat treatment temperature of WO_3 nanorods. The optimized NO_2sensor（400-℃-annealed WO_3 nanorods） showed an ultra-high sensor response of 3.2 and short response time of 1 s to 5-ppm NO_2. In addition, the 400-℃-annealed sample exhibited more stable repeatability.Furthermore, dynamic responses measurements of annealed samples showed that all the annealed WO_3 nanorods sensors presented p-type behaviors. We suppose the p-type behavior of the WO_3 nanorods sensor to be that an inversion layer is formed in the space charge layer when the sensor is exposed to NO_2 at room temperature.Therefore, the 400-℃-annealed WO_3 nanorods sensor is one of the most energy conservation candidates to detect NO_2 at room temperature.展开更多
We prepared macro-porous silicon（MPS） by electrochemical corrosion in a double-tank cell on the surface of single-crystalline P-type silicon.Then,nano-WO_3 films were deposited on MPS layers by DC facing target reac...We prepared macro-porous silicon（MPS） by electrochemical corrosion in a double-tank cell on the surface of single-crystalline P-type silicon.Then,nano-WO_3 films were deposited on MPS layers by DC facing target reactive magnetron sputtering.The morphologies of the MPS and WO_3/MPS samples were investigated by using a field emission scanning electron microscope.The crystallization of WO_3 and the valence of the W in the WO_3/MPS sample were characterized by X-ray diffraction and X-ray photoelectron spectroscopy,respectively. The gas sensing properties of MPS and WO_3/MPS gas sensors were thoroughly measured at room temperature. It can be concluded that：the WO_3/MPS gas sensor shows the gas sensing properties of a P-type semiconductor gas sensor.The WO_3/MPS gas sensor exhibits good recovery characteristics and repeatability to 1 ppm NO_2.The addition of WO_3 can enhance the sensitivity of MPS to NO_2.The long-term stability of a WO_3/MPS gas sensor is better than that of an MPS gas sensor.The sensitivity of the WO_3/MPS gas sensor to NO_2 is higher than that to NH_3 and C_2H_5OH.The selectivity of the MPS to NO_2 is modified by deposited nano-WO_3 film.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60771019,61271070,and 61274074)the Tianjin Key Research Program of Application Foundation and Advanced Technology,China(Grant No.11JCZDJC15300)
文摘Hexagonal WO_3 nanorods were synthesized through a facile hydrothermal method. The nanorods properties were investigated by scanning electron microscope（SEM）, transmission electron microscope（TEM）, energy dispersive spectroscopy（EDS）, and x-ray diffraction（XRD）. The NO_2-sensing performances in terms of sensor response, response/recovery times and repeatability at room temperature were optimized by varying the heat treatment temperature of WO_3 nanorods. The optimized NO_2sensor（400-℃-annealed WO_3 nanorods） showed an ultra-high sensor response of 3.2 and short response time of 1 s to 5-ppm NO_2. In addition, the 400-℃-annealed sample exhibited more stable repeatability.Furthermore, dynamic responses measurements of annealed samples showed that all the annealed WO_3 nanorods sensors presented p-type behaviors. We suppose the p-type behavior of the WO_3 nanorods sensor to be that an inversion layer is formed in the space charge layer when the sensor is exposed to NO_2 at room temperature.Therefore, the 400-℃-annealed WO_3 nanorods sensor is one of the most energy conservation candidates to detect NO_2 at room temperature.
基金Project supported by the National Natural Science Foundation of China(No.60771019)the Tianjin Key Research Program of Application Foundation and Advanced Technology,China(No.11JCZDJC15300)
文摘We prepared macro-porous silicon（MPS） by electrochemical corrosion in a double-tank cell on the surface of single-crystalline P-type silicon.Then,nano-WO_3 films were deposited on MPS layers by DC facing target reactive magnetron sputtering.The morphologies of the MPS and WO_3/MPS samples were investigated by using a field emission scanning electron microscope.The crystallization of WO_3 and the valence of the W in the WO_3/MPS sample were characterized by X-ray diffraction and X-ray photoelectron spectroscopy,respectively. The gas sensing properties of MPS and WO_3/MPS gas sensors were thoroughly measured at room temperature. It can be concluded that：the WO_3/MPS gas sensor shows the gas sensing properties of a P-type semiconductor gas sensor.The WO_3/MPS gas sensor exhibits good recovery characteristics and repeatability to 1 ppm NO_2.The addition of WO_3 can enhance the sensitivity of MPS to NO_2.The long-term stability of a WO_3/MPS gas sensor is better than that of an MPS gas sensor.The sensitivity of the WO_3/MPS gas sensor to NO_2 is higher than that to NH_3 and C_2H_5OH.The selectivity of the MPS to NO_2 is modified by deposited nano-WO_3 film.
