| ZnO with wurtzite structure is a kind of direct wide-band gap n-type semiconductor material.It's forbidden band width is 3.37 eV at room temperature and the exciton binding energy is as much as 60 me V.These unique properties make it a star semiconductor material.Due to the large specific surface area,high surface activity and excellent photoelectric characteristics,one dimensional ZnO nanowires have been widely studied.Among them,ZnO nanowire schottky barrier devices demonstrated excellent performance in the UV detection,gas sensor and et al.Lots of research indicated that oxygen adsorbed on the nanowire surface play a important role in the barrier modulation.But,in the schottky barrier formed between noble metals such as Au & Pt and ZnO nanowires,both the work function difference of metal-semiconductor and adsorbed oxygen dominates electrical transport properties of barrier.However,this hindered the further Research of the mechanism of schottky barrier controlled by adsorbed oxygen and developing control methods of adsorbed oxygen.Therefore,in this paper,using low work function metal Ag as metal electrode,we prepared ZnO nanowires with good performance,constructed single-nanowire schottky devices,and developed a new method to modulate the Schottky barrier(SB)by applying bias and UV irradiation at the same time.On this basis,we developed a new type of the Schottky device,which can be used as a “AND gate” in digital logic circuit.Finally,the working mechanism of the device is explained.In the first chapter,we firstly introduced the related knowledge of nanomaterials simply,and secondly,we emphasized the research progress of one-dimensional ZnO nanodevices and the modulation methods of schottky barrier.On this account,we proposed the topic,research purpose and main content of this paper.In the second chapter,we successfully prepared the ZnO nanowires on the Silicon substrate through chemical vapor deposition method(CVD).Then,the morphology,crystallinity and crystal structure of ZnO nanowires were characterized by SEM,XRD and HRTEM.The results showed that these nanowires had high yield and good crystallinity,followed the vapor-liquid-solid(V-L-S)growth mechanism.At the same time,a method of preparing one-dimensional nanodevices were explored by using nanoscale Ag ink as electrodes and assisted by three-dimensional movable platform and microscope.The method is simple,efficient and cheap.A series of electrical and photoelectric properties of the devices fabricated by this new method had been tested.The results showed that the devices had good reliability.In the third chapter,we developed a new type of resistive switching devices under the dual modulation of ultraviolet light and applied bias,which can be used as the “AND” gate in digital circuit.Then,the current-voltage loop and the resistive switch retention characteristics of the device were tested under different UV light irradiation intensity and in the different atmosphere.According to the test results,our devices' working mechanism can be explained by the microscopic desorption mechanism.That is to say,only when the combined action of both the optics and electronics,the absorbed oxygen would be desorbed.Based on the new type of resistance switch device,we developed two new types of devices:bidirectional controlled rectifier diode and logic gate circuit with electric and Light common control.The former,the diode direction of rectification can be controlled through the polarity of voltage.The later,we can input the two different types of signals: optical signal and electrical signal,to perform the logical "and" gate operations. |
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