Preparation, Doping Vario-property And Optoelectrical Device Study Of Vanadium Dioxide Film

Recently,with the development of digital industry and the popularization of smart devices,the semiconductor fabrication and very-large-scale integration circuit industry have developed rapidly,which push the silicon-based semiconductor technology to a new high.Nowadays,the feature size of chip has been reduced to 5nm,which is developed towards 3 nm.However,the reduced feature size not only challenges the physics limit,but also causes many parasitic issues,such as the short-channel effect,the drain induced barrier lowering effect,the weaker control of gate-to-channel,the larger leakage current and power consumption,which restrict the development of Moore's law.In order to solve these problems,on the one hand,researchers optimize or redesign the device structure and improve the fabrication process to alleviate and balance the contradiction.On the other hand,there are some new high-performance semiconductor materials have been selected to partially or completely replace the silicon-based semiconductor.Among them,oxide semiconductor materials with metal-insulator transition?MIT?,especially vanadium dioxide?VO₂?,have attracted a lot of interest.VO₂ is a typical strongly correlated electronic material with the abrupt variations in resistivity and infrared transmittance,whose critical temperature(T_MIT)is closest to the room temperature.VO₂ has the good compatibility with some applications,such as the electronic switche,storage device,smart window and photodetector.In view of this,our study focuses on the VO₂,and explores the film preparation process and the influence of element doping on the phase transition of VO₂.Meanwhile,the study also expands its application in the field of optoelectronics.Specific study contents include:?1?VO₂ films are successfully grown on the different substrates by pulse laser deposition and subsequent thermal-annealing.The crystal structure and metal-insulator transition of the prepared VO₂ film with the influence of the substrate are studied systematically.The electronic-controlled phase transition of the VO₂ film is further explored.The successful preparation of the high-quality VO₂ film is a difficulty,which is also the basis for further investigation of the property and application.The quality and physical characteristic of the thin film are closely related to the control of growth parameters and the selection of substrates.In this study,pulse laser deposition and thermal-annealing are performed to successfully grow the high-quality and pure VO₂films on the completely different substrates,which are?0001?Al₂O₃ and SiO₂/p⁺-Si.The metal-insulator transition temperatures of VO₂ films are all around 343 K,with3-4 orders of magnitude resistance change.It indicates that the substrate hardly affects the properties of the VO₂ film,and the deposition method is universal.Furthermore,based on the VO₂ two-terminal device,the study of the electronic-controlled phase transition shows that the effect of electric-field becomes more significant as the channel length is reduced.This study is beneficial to further understand the mechanism of electronic-driven phase transition.?2?The V_1-xW_xO₂?0.16?x?0.20?films are successfully prepared through the above-mentioned deposition method.The effects of heavy tungsten doping on the metal-insulator transition of VO₂ are systematically studied.The interband electronic transition and orbital structure variation under the heavy W doping are further analyzed.Vanadium dioxide?VO₂?with a metal-insulator transition?MIT?has been supposed as a candidate for optoelectronic devices.However,the MIT temperature(T_MIT)above room temperature limits its application scope.Here,high-quality V_1-xW_xO₂ films are prepared by pulsed laser deposition,thereby realizing the regulation of T_MIT.On the basis of temperature-dependent transmittance and Raman spectra,it is found that T_MITIT increases from 241 to 279 K,when increasing the doping concentration in the range of 0.16?x?0.20.The interband electronic transitions and orbital structures of V_1-xW_xO₂ films are investigated via fitting transmittance spectra.Moreover,with the aid of first-principles calculations,an effective orbital theory is proposed to explain the unique phenomenon.When the W doping concentration increases,the?^*and d_?orbitals shift toward the?orbital.Meanwhile,the energy gap between the?^*and d_?orbitals decreases at the insulator state.It indicates that the bandwidth is narrowed,which impedes MIT.In addition,the overlap of the?^*and d_?orbitals increases at the metal state,and more doping electrons occupy the?^*orbital induced by increasing W doping concentration.It manifests that the Mott insulating state becomes more stable,which further improves T_MIT.The present work provides a feasible approach to tune T_MIT via orbital variation and can be helpful in developing the potential VO₂-based optoelectronic devices.?3?GaSe/VO₂ van der Waals heterostructure is successfully prepared by the above-mentioned deposition method and mechanical exfoliation.The rectification and photoresponse properties of the device are systematically studied.The manipulation of the metal-insulator transition on its photoresponse performance is further explored.Van der Waals?vdW?heterostructures,integrated two-dimensional?2D?materials with variously functional materials,provide a distinctive platform for next-generation optoelectron ics with unique flexibility and high performance.However,exploring the vdW heterostructures combined with strongly correlated electronic materials is hitherto rare.Herein,a novel temperature sensitive photodetector based on the GaSe/VO₂ mixed-dimensional vdW heterostructure is discovered.Compared with previous devices,our photodetector exhibits excellently enhanced performance,with external quantum efficiency up to 109.6%and the highest responsivity(358.1 mA·W^-1)under a 405 nm laser.Interestingly,we show that the heterostructure overcomes the limitation of a single material under the interaction between VO₂ with GaSe,where photoresponse is highly sensitive to temperature and can be further shut at the critical value.The metal-insulator transition of VO₂,which controls the peculiar band-structure evolution across the heterointerface,is demonstrated to manipulate the photoresponse variation.This study enables us to elucidate the method of manipulating 2D materials by strongly correlated electronic materials,paving the way for developing the high-performance and special optoelectronic application.