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Study On The Synthesis And Photoluminescence Property Of Necklace-Like SiC/SiO2 Heterojunctions Via A Molten Salt Mediated Method

Posted on:2018-10-27Degree:MasterType:Thesis
Country:ChinaCandidate:W LiFull Text:PDF
GTID:2321330515973383Subject:Materials science
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Silicon carbide?SiC?,as the third generation of semiconductors,exhibits not only wide band gap,high electrical breakdown voltage,and high electron saturation rate,but also remarkable physical and chemical properties,for instance,high mechanical strength,excellent thermal stability,good oxidation resistance,and corrosion resistance.Therefore,it could be served as electronic devices in high power integrated circuit,as well as in harsh working environment.Besides,the formation of one-dimensional structure could contribute to the electrical performance,optical performance and mechanical properties of SiC materials.Nevertheless,the morphology,structure,productivity and performance of products are limited to the synthetic methods and processes.Just in order to improve this sort of adverse relationship,in this work,carbon burial process?without protective gas?was adopted to large scale synthesis necklace-like Si C/SiO2 heterojunctions at a relative lower temperature,and the influences of raw materials,molten salts,and process parameters on the morphology and structure of as-synthesized products were fully investigated.Meawhile,based on these results,the photoluminescence property of necklace-like SiC/SiO2 heterojunctions was characterized in detail.Additionally,the growth mechanism was studied.The main conclusions are summarized as follows:Necklace-like SiC/SiO2 heterojunctions were largely synthesized with Si,SiO2,and graphite when the mass ratio of NaCl to NaF is 3:1 and the silicon source to molten salt is 1:1.Meanwile,the productivity tends to reduce along with the increase of both ratios.Additionally,the productivity and crystallization degree of the ?-SiC reflects a downward trend along with the reduction of molten salt quantity.Necklace-like SiC/SiO2 heterojunctions were largely synthesized via molten salt mediated vapor reaction technique at 1200°C.The length and diameter of SiC is about hundreds of micrometers and 300500 nm,respectively,and the diameter of the spherical particles is 13 ?m.Meanwhile,the diameter of the spherical particles the thickness of amorphous shell decrease along with the increase of temperature?12001400°C?and holding time?23 h?.The as-synthesized SiC/SiO2 heterojunctions are composed of ?-SiC chains and amorphous SiO2 beans.Besides,the ?-SiC tends to grow along the [111] crystal orientation,and the formation of shell-core structure could contribute to the optical performance of SiC materials.Necklace-like SiC/SiO2 heterojunctions also exhibite a strong PL emission in the range of 350600 nm and peaks at around 400415 nm,which display a significant blue-violet photoluminescence properties.Moreover,the luminescence frequency of the heterojunctions is inclined to decline along with the reduction of molten salt,and the intensity is apt to raise in pace with the reduction of amorphous shell thickness.The growth mechanism of the as-synthesized SiC/SiO2 core-shell chains is most likely controlled by vapor–solid mechanism and Marangon convection at first stage,while the formation of SiO2 beans can be mainly attributed to the Rayleigh instability and surface tension in the second stage.
Keywords/Search Tags:SiC/SiO2 heterojunctions, Molten salt method, Chemical vapor deposition, Photoluminescence property
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