Catalyst-Free Growth Of A Zn₂GeO₄ Nanowire Network For Solar-Blind Deep UV Detection

Solar-blind deep-ultraviolet?DUV?photodetectors have attracted wide attention because of their extensive military and civil applications.The ternary oxide Zn₂GeO₄ is an ideal material with a wide bandgap?E_g=4.69 eV?.In this work,DUV photodetectors based on a ternary Zn₂GeO₄ nanowire?NW?network were fabricated on SiO₂/Si substrates.Reactive ion etching of the SiO₂/Si wafer was used to synthesize the NW network to avoid contamination of the Au catalyst during synthesis of the Zn₂GeO₄ NW network via high-temperature chemical vapor deposition.Based on this method,we studied the photoelectric performance of the synthesized Zn₂GeO₄ NW network,and proposed two methods to improve its photoelectric performance.The contents of the paper are as follows:1.The research background,significance and development status of the subject are introduced.It mainly summarizes the crystal structure and application of Zn₂GeO₄nanomaterials and the related knowledge of DUV detector,and gives a brief description of the work content of this paper.After that,the performance indicators of the UV photodetector are introduced in detail,which provides a reference for the following performance analysis of Zn₂GeO₄ NW network DUV photodetector.2.Several common synthetic methods of Zn₂GeO₄ NWs are introduced,and the classification,characteristics and growth mechanism of vapor deposition are emphatically introduced in this paper.Then,the application,principle and instrument parameters of several Zn₂GeO₄ NW characterization methods are introduced in detail,which lays a foundation for the later experimental part.3.The experimental process of preparing Zn₂GeO₄ NW network was introduced in detail and some samples were prepared according to this method.Characterization shows that the absorption peaks of Zn₂GeO₄ NW are located at 235 nm,the absorption band edge is 257 nm,and the corresponding bandgap is 4.91 eV.Under the excitation of 310 nm He-Cd laser,two emission peaks are generated,397 nm and 515 nm.4.The Zn₂GeO₄ NW network was fabricated into a DUV photodetector and tested by a semiconductor analyzer.The detection cut-off wavelength of Zn₂GeO₄ NW network photodetector is 253 nm,the external quantum efficiency is 46.5%,the responsivity is9.5×10^-2 A·W^-1 and the signal-to-noise ratio is 46 dB at 254 nm.The response time is 600 ms and the recovery time is 250 ms.Then the transmission mechanism of Zn₂GeO₄ NW photodetector was analyzed.5.The performance of Zn₂GeO₄ NW DUV photodetector was improved by surface O₂plasma treatment and surface Al nanoparticle modification.It is found that surface O₂ plasma treatment can only enhance the photocurrent of the photodetector in a short time,while Al nanoparticle modification can greatly increase the photocurrent and reduce the dark current without affecting the response speed.The internal transmission mechanism of these two methods is also analyzed.In summary,the morphology of Zn₂GeO₄ NW network prepared without catalyst and the photoelectric properties of deep ultraviolet devices were studied by theoretical analysis and experimental measurements.At the same time,two methods to improve the photoelectric properties of devices are also provided,which provide important references for the preparation of nanomaterials and the research of deep ultraviolet photodetectors.