Research On Controllable Growth And Fabrication Of Si Nanowires

As a new type of nanomaterial,silicon nanowires（Si NWs）have become a hot research object due to its unique optical,electrical,mechanical and chemical properties.Processing patterned regions,dense and uniform Si NWs is the key to the application of nanowires in various fields.The solid-liquid-solid growth mechanism is one of the important methods for preparing Si NWs from bottom to top.It has the advantages of simple silicon source material,safe reaction gas,and high density of Si NWs for growth preparation.The annealing temperature for conventional solid-liquid-solid growth of Si NWs is close to 1000°C,generally.The violent reaction environment brings difficulties to the study of growth mechanism and the quality of nanowires.Therefore,the growth of nanowires of high density and patterned regions,in low temperature,has become the focus of research.In this paper,a new method for the preparation of low temperature catalytically grown Si NWs is proposed under the solid-liquid-solid（SLS）growth mechanism.The growth of Si NWs at a lower temperature（600°C）is achieved by a mixture of a gallium-based alloy（liquid metal）and gold（Au）.Considering the fluidity of the liquid metal,the pattern distribution of the liquid metal is completed on the gold-plated silicon wafer to realize the control of the growth region of the Si NWs.Firstly,based on the solid-liquid-solid growth mechanism and the theoretical analysis of catalytic metals,it is proposed to grow Si NWs by mixing the gallium-based alloy with Au to reduce the temperature required for growth.The model of single prong and multiprong is established.Using the fluidity of liquid metal,a direct writing method based on flexible micron tubes for liquid metal distribution is proposed.Different distribution strategies are studied for points and lines.Based on this theory,the growth platform of Si NWs and the liquid metal direct writing motion control platform are built.Secondly,Au and mixed metal catalyzed growth of Si NWs are used to investigate the effects of different annealing temperatures on the growth results.And the feasibility of the preparation method of low temperature mixed metal catalytic growth of Si NWs is verified.By changing the annealing temperature,N₂ flow rate,growth time and heating process during the growth process,the effects of different experimental parameters on the preparation of Si NWs were investigated to control the diameter and density of Si NWs.Finally,the contact angle between different material substrates and liquid metal is compared to investigate the wettability of liquid metal and substrate,and the feasibility of writing liquid metal method is verified.Based on the distribution strategy proposed in this paper,the distribution of gallium-based alloys with point and line features is completed.Dense and uniform Si NWs with controllable regions are obtained after annealing.The size,density,elemental composition,structure,photoluminescence properties of the Si NWs are characterized.This paper provides a novel method for processing Si NWs at low temperature via solid-liquid-solid mechanism.Using the fluidity of liquid metal,flexible micron tubes is used to achieve graphical direct writing of catalytic metal.This method provides an innovative,simple,flexible and high yield fabrication of two-dimensional（2D）nanostructures from the bottom up,which is an appealing alternative to conventional top-down processes.