Fabrication And Ultraviolet Detection Properties Of ZnO/ZnS Core/shell Nanowires

Due to the large specific surface area that massive materials does not have, ZnO nanowires have manycharacteristics which like surface effect, small size effect and macroscopic quantum tunnel effect and so on.These excellent performance make ZnO nanowires widely used in light-emitting diodes, field effecttransistor, chemical/gas sensor, photoelectric detector and flat panel display, etc.Although one-dimensional nano optoelectronic devices emerge many excellent properties in ultraviolet (UV) photoelectric devices, people conducted many research work about the performance ofone-dimensional UV detector based on semiconductor nanowires schottky barrier, and made significantprogress, but there are still some problems.First, The studies have found that the main factor influencing the optical detection was schottkybarrier, Schottky barrier height was controlled by surface states. However, due to the surface states of theZnO nanowires configuration is more complex, making its optical transport behavior lack of effectivecontrol, which allows the performance of the device show instability, and cannot repeat.Second, The shell of ZnO core-shell heterostructure nanowires can be passivation of the surface statesof ZnO, resulting in the photoelectric characteristics is different from the single system. But nanowiredevice based on single core-shell structure of photovoltaic transport characteristics and the process ofcharge separation and transport is still not very clear.Based on the above problems, in this paper, the Schottky barrier UV detector devices were fabricated by aligning single ZnO nanowire across paired Au electrodes using dielectrophoresis. Then we studied theeffects of adsorbed oxygen of nanowire surface on the Schottky Barrier (SB). In addition, we made the SBUV detectors by using ZnO/ZnS core-shell nanowire with type II band alignment structure. In the opticalexcitation condition, the electron and hole can well controlled in this structure, which can further improvethe performance of UV detector. On the basis, the ZnO nanowire Schottky barrier UV detector with highsensitivity and fast recovery time is developed.This paper main work includes the following aspects:In the second chapter, we synthesised the ZnO nanowire arrays along the c-axis, which weregrown on sapphire(11-20) crystal substrate by Au catalyst assisted vapor liquid solid (VLS) and have agood crystalline performance. Then, by using chemical bath deposition and elemental substitutionmethod, the ZnO/ZnS core-shell nanowire array with type II band alignment structure was synthesised.In the third chapter, firstly, the Schottky barrier UV detector devices were fabricated by aligningsingle ZnO nanowires across paired Au electrodes using dielectrophoresis. Then we studied thecurrent-voltage(I-V) curve characteristics and light current change with time of the ZnO nanowiresSchottky Barrier UV detector, after that discussed the effects of adsorbed oxygen of nanowire surface onthe Schottky Barrier at different atmosphere and studied the optical current mechanism and recoveryprocess in-depth. It is pointed out that the current tunneling mechanism is the key reason why nanowiresSchottky barrier UV detector has a short response time.After that, we used S element to replace the O element on the surface of ZnO nanowires by meansof elemental substitution, by which we fabricated the ZnO/ZnS core-shell nanowire Schottky Barrier UVdetector. Then we studied the current-voltage(I-V) curve characteristics and light current change with time of the ZnO/ZnS core-shell nanowires Schottky Barrier UV detector to discusse the optical currentmechanism and recovery process. On this basis, the ZnO nanowire Schottky barrier UV detector withhigh sensitivity and fast recovery time is developed.