Study On The Growth Mechanism And Photoelectric Application Of Vanadium Oxide

Vanadium oxide has attracted much attention due to its unique metal-insulating phase transition?MIT?characteristics,and has been widely used in the fields of photodetection,field effect transistors,thermal/optical switches.However,due to the thermodynamic instability of vanadium oxide during the growth process and up to thirteen competing vanadium oxide phases,the high-quality,single-phase vanadium oxide synthesis faces great challenges,especially for the synthesis of mixed valence vanadium oxides(such as V₆O₁₃)is facing huge challenges,and it has become a major problem that restricts the research of vanadium oxide properties and applications.The key to solving the above problems lies in mastering the evolution of mesophases during the growth of vanadium oxide,understanding its growth thermodynamics,and knowing the growth mechanism of vanadium oxide crystals.In this paper,the growth mechanism,characteristic modulation and application of vanadium oxide(VO₂ particles and V₆O₁₃crystals)were studied.1.Study on VO₂ particle growth mechanism and its phase transition regulation.First,a simple vapor deposition and annealing strategy was used to prepare a dispersed,pure phase and uniform VO₂ particle film.The evolution process of the V₂O₅precursor film to the VO₂ particle film was systematically studied by a kind of in-situ monitoring growth technology.The results show that the precursor film undergoes a synergistic process of solid state dewetting and pyrolysis during annealing to form dispersed VO₂ particles,and then undergoes a crystallization process to achieve the desired orientation.Through analysis,we propose a solid-state dewetting growth mechanism,and a phase diagram was used to explain the rule of VO₂ particle growth.Secondly,under the guidance of the growth mechanism and phase diagram,we control the thickness of the precursor film to prepare VO₂ particle films with controllable particle size,and determine the phase transition behavior of VO₂ particle films with different particle diameters by means of variable temperature Raman testing.The experiment found that the modulation of the phase transition behavior of VO₂particles can be achieved through the adjustment of the particle size.In the range of 220nm to 1.05?m,the MIT temperature and hysteresis decrease with the increase of the particle size.in which the average particle size is 1.16?m,and the excellent phase transition behavior of low phase transition temperature?41??and zero hysteresis is realized.Finally,with the support of characterization data such as XRD,Raman,XPS,and SEM,the modulation effect of particle size-related crystallinity,strain,and defects on the phase transition behavior of VO₂ particles was analyzed.The results show that at larger sizes,Stress dominates MIT behavior,and at smaller dimensions,surface tensile stress and surface defect effects become more prominent.2.Study on the growth kinetics and photodetection of V₆O₁₃ crystal.First,V₆O₁₃ layered crystals with high growth orientation?00l?were prepared by simple drop coating and annealing;which size is controllable and the maximum size can reach mm grade,which solves the difficult problem of producing high quality V₆O₁₃crystals in the laboratory at present.Secondly,with the support of real-time in-situ crystal growth technology,we intuitively and dynamically observed the growth process of V₆O₁₃ crystal and the evolution of mesophase.The results show that the melting and decomposition of V₂O₅starts as a synchronous process of V₆O₁₃ nucleation.The melting and endothermic process provided the main driving force for the rapid growth of V₆O₁₃ crystal along the melting/solid interface.At the same time,combined with the comprehensive thermal analysis,the growth thermodynamics quantitatively was analyzed.Here,we propose a new growth mechanism----Melting driven&pyrolysis growth?MDP?.Then,the as-prepared V₆O₁₃ crystals were prepared into suspended two-terminal photodetectors,the photoelectric properties of V₆O₁₃ were first investigated;the results showed that the optoelectronic devices based on V₆O₁₃ crystals exhibited excellent photoelectric properties such as high response speed?42 ms?,high response?10-100A/W?,and wide spectrum?0.4-8.8?m?.Finally,the photoresponse mechanism of the V6O13 photodetector device was investigated using a scanning photoelectric microscope test;photocurrent imaging data analysis indicates that V₆O₁₃ crystals exhibit excellent optoelectronic properties derived from the synergistic effect of the photoelectric?PV?effect and the bolometer?BOL?effect.