Research On The Preparation Process Of Silicon Nanowires

Silicon nanowire,which is different from other low dimensional nanomaterials,has unique optical,electrical and field emission properties,making it play a special role in photovoltaic devices,field emission devices and electron transport.In addition,silicon nanowire also has the semiconductor properties of silicon materials,which can be compatible with the existing semiconductor technology,and further demonstrates the advantage that other nanomaterials can't achieve.Silicon nanowire is widely used in solar cells and sensors.At present,although silicon nanowire has made great progress in research,there are still many urgent problems to be solved from the actual industrial large-scale production and application.For example,the preparation process of silicon nanowire is immature and can not achieve mass production.At the same time,the cost of preparation is always high,and it is difficult to realize industrial production.Therefore,it is of great significance to select suitable silicon sources and study the preparation technology of silicon nanowire in detail,so as to achieve the industrial application of silicon nanowire.In this paper,the silicon nanowire is grown by a cheap silicon tetrafluoride?SiF₄?gas as a silicon source,which is the by-product of phosphorus chemical industry.On the one hand,it improves the economic benefit of the phosphorus chemical industry.On the other hand,it provides a new way for the preparation of silicon nanowire.This paper mainly consists three parts:in the first part,the synthesis of silicon nanowire is preliminarily explored by using the gas-liquid-solid growth mechanism?VLS?,atmospheric pressure chemical vapor deposition?CVD?,and silicon tetrachloride?SiCl₄?as silicon source.The results show that the silicon source grown on silicon nanowire comes from the gaseous silicon source provided by experiments.The importance of annealing treatment in the preparation of silicon nanowire is confirmed.In the second part,based on the above experiments,we study the process of growing silicon nanowire with SiF₄ gas,which purity is 99.9%?abbreviation 3N?.In this part,fluorosilic acid?H₂SiF₆?was used as the precursor to obtain the SiF₄ gas,which was used as silicon source.The route of the synthesis of silicon nanowire was studied in detail.The effects of annealing time,gas flow rate,reaction temperature and reaction time for the growth of silicon nanowire were investigated.The results show that the annealing time mainly affects the number and size of the alloy droplets.The carrier gas flow mainly affects the retention time of the silicon source on the alloy droplets and the concentration of the silicon source.The reaction temperature could not be less than 1000?.The diameter and yield of the silicon nanowire will increase,when the reaction time increases.In the third part,silicon nanowire was grown with SiF₄ gas to further confirm the growth mechanism of silicon nanowire under this system.SiF₄ gas purity is 99.999%?abbreviation 5N?.The results show that a part of the SiF₄ molecules first react with the silicon on the substrate to produce SiF₂ in the formation of silicon nanowire.The active SiF₂ molecules with Si F₄molecules are further adsorbed on the surface of the catalyst alloy droplets,which forms silicon nanowire.