Construction And Performance Tuning Of SnO₂ Nanofiber Photodetectors

With the development of science and technology,photodetectors which can detect a specified electromagnetic wave have been widely applied in national defense,military,aerospace,environmental detection,biomedical,optical communication and chemical analysis.One-dimensional metal-oxides(1D-MO)nanostructure has been regarded as one of the most promising channel candidates for high-performance photodetectors due to their outstanding electronic properties,low-cost and environmental stability.Compared with In2O3 and Zn O nanofibers,SnO₂ nanofibers are more suitable as the channel materials for photodetectors due to the advantages of high carrier concentration,high photosensitivity,large reserve,low cost and stability.However,1D pure SnO₂ nanofibers photodetectors still suffers from the disadvantages of high operating voltage and dark current,high energy consumption,slow response/recovery speed,narrow spectral response range and so on.Therefore,it is significant to improve the performance of SnO₂ nanofibers photodetectors.In this thesis,the performance of photodetectors were largely improved by doping and fabricating heterojunction,and the detailed works are as follows.1D SnZnO nanofibers with different Sn:Zn mole ratio were synthesized by doping the element of Zn into SnO₂ NFs.When the mole ratio of Sn:Zn equals to 8:2(Sn8Zn2Ox),the Sn8Zn2 Ox nanofibers transistor exhibits the optimal electrical performance,with a positive threshold voltage(VTH)due to relatively low carrier concentration,and a high Ion/Ioff of5.87×106.Meanwhile,the corresponding Sn8Zn2 Ox nanofibers photodetector exhibits low dark current(9.6×10-12 A)under the gate voltage of 0 V,a high photosensitivity(5.2×104),high responsiveness 3.4 A W-1,and high detectivity 2.73×1017 Jones under 280 nm irradiation.After continuous 500 s testing under 280 nm irradiation and dark,the current maintains stable(80%).Additionally,it is found that the Sn8Zn2 Ox nanofibers phototransistors have good memory characteristics and stability.After 3 repeated test of optical writing and electrical erasure process ⁹0% photocurrent was maintained.The results provide the possibility of Sn₈Zn₂O_x nanofibers for the preparation of biomimetic memory devices.Secondly,in order to reduce the operating voltage of the photodetector,improve the response/recovery speed,and broaden the optical response range of 1D SnO₂ photodetector,we fabricated the SnO₂ nanotubes(NTs)/perovskite heterojunction photodetector on FTO glass substrate.Due to the Schottky junctions between SnO₂ NTs and FTO with different work functions,the operating voltage of the device was as low as 0.42 V.In addition,combined with the advantages of low defect and fast response of perovskite,heterojunction photodetector exhibits a fast response/recovery time of 0.075/0.04 s,wide spectral response range of 220-800 nm and a high photosensitivity of 2×103.The outstanding performance is mainly attributed to the formation of type-? heterojunctions between SnO₂ NTs and perovskite,which are able to facilitate the separation of photogenerated carriers.All the results indicate that the rational design of 1D-MO/perovskite heterostructure is a facile and efficient way to achieve highperformance photodetectors.