Recently, one-dimensional (1D) nanostructure field-effect transistors (FETs) have attracted much attention because of their potential application in gas sensing. Micro/nanoscaled field-effect sensors combine the advantages of 1D nanostructures and the characteristic of field modulation. 1D nanostructures provide a large surface area-volume ratio, which is an outstanding advantage for gas sensors with high sensitivity and fast response. In addition; the nature of the single crystals is favorable for the studies of the response mechanism. On the other hand; one main merit of the field-effect sensors is to provide an extra gate electrode to realize the current modulation; so that the sensitivity can be dramatically enhanced by changing the conductivity when operating the sensors in the subthreshold regime.[1] We fabricated the room-temperature gas dielectric CuPc nanowire FET SO2 sensors with high sensitivity, low detection limit, fast response and complete recovery. The detect limitation is down to sub ppm levels (0.5 ppm) with the sensitivity of 119% and high resolution of 100 ppb. The sensitivity is as high as 764% in 20 ppm SO2. The response and recovery time in 0.5 ppm SO2 are only 3 and 8 min, respectively. The high performance of the sensor originates from the exposed conductive channel by using a gas dielectric.[2] We also fabricated a SnO2 nanobelt field effect transistor sensor, with the SnO2:Sb nanobelts serving as the source and drain electrodes. An anomalous feature of the device is that the threshold voltage shows the negative shift upon exposure to NO2. The comparative results from the other two types of devices, including SnO2 nanobelt with metal film electrodes and SnO2:Sb nanobelt with metal film electrodes, reveal that the interface between the SnO2:Sb nanobelt electrodes and the SnO2 nanobelt is responsible for the improved carrier injection efficiency and the negative shift in the threshold voltage. Such a response mechanism results in the detection limit for NO2 down to 10 ppb, with a sensitivity as high as 7.16×105% at room temperature.[3]
References [1] Zhao XL, Cai B, Tang QX, Tong YH, Liu YC, 2014. One-Dimensional Nanostructure Field-Effect Sensors for Gas Detection. Sensor 14: 13999-14020. [2] Shaymurat T, Tang QX, Tong YH, Dong L, Liu YC, 2013. Gas Dielectric Transistor of CuPc Single Crystalline Nanowire for SO 2 Detection Down to Sub-ppm Levels at Room Temperature. Adv. Mater. 25: 2269–2273. [3] Cai B, Zhao XL, Pei TF, Toninelli E, Tang QX, Tong YH, 2014. Conductive SnO2:Sb nanobelts as electrodes for detection of NO2 in ppb level with ultrahigh sensitivity. Appl. Phys. Lett. 104: 073112.