Experimental And Theoretical Research On One Dimensional Semiconductor Nanowires Based On Vapor-Liquid-Solid Mode

With the continuous improvement of living standards,the demand for high-performance MEMS and electronic products is increasing.However,the improvement of the performance of those products is inseparable from the development of related materials.Nanomaterials refer to artificial composites of supernormal physical properties that natural materials do not possess,which are divided into two dimensional films,one dimensional nanowires and zero dimensional quantum dots.One dimensional semiconductor nanowire,which are semiconductor nanowires,have the characteristics of small volume,light weight and low power consumption.They can effectively improve the information transmission,storage and processing ability and intelligence level in the control system.Therefore,in this dissertation,one dimensional semiconductor nanowires are the main research contents,using the Metal Organic Chemical Vapor Deposition(MOCVD)technology to research the homostructure,heterostructure nanowire and the nanowire grown on heterosubstrates.The effects of V/III and growth temperature on the morphology and crystal quality of one-dimensional semiconductor nanowires grown by Au-assisted catalysis and self-catalysis are systematically studied.The reasons for the lateral rotation of axial heterostructure nanowires at high temperature are analyzed theoretically.The “conical” and “step” morphologies of semiconductor nanowires on the surface of heterostructure substrate are investigated in detail.The main contents of this dissertation are as follows:The effects of substrate doping,V/III and growth time on the morphology,crystal structure and crystal quality of GaAs nanowires grown in the gold assisted catalyszed Vapor-Liquid-Solid mode are researched.Those nanowires grown on the substrate with larger doping concentration have smaller density of the metarmaterial and greater growth rate.V/III can also affect the growth rate of nanowires: the growth rate of nanowires with smaller V/III is larger than that with higher V/III.Long growth time will result in catalyst poisoning,and the height of the GaAs nanowire will be hardly changed after reaching a certain value.In this dissertation,the effects of V/III and growth temperature on InP semiconductor nanowires are researched by combining the self-catalyzed technology with InP nanowire.The growth rate of InP nanowires grown by self-catalyzed technology is inversely proportional to the V/III.The maximum growth rate of InP nanowires(430?)is neither at lower growth temperature(380?)nor at higher growth temperature(480?).The segregation due to the instability of self-catalyzed catalysts makes the lateral growth of InP nanowires more seriously.The effects of V/III on the axial heterostructure of GaAs/InAs and GaAs/InP semiconductor nanowires and the effects of growth temperature on the radial heterostructure of GaAs/InAs and GaAs/InP semiconductor nanowires are investigated.The growth heights of the axial heterostructure nanowires are inversely proportional to their V/III.When the V/III is larger,the number of atoms entering the catalyst is less and the height of the nanowire is smaller.Increasing the growth temperature of nanowires can inhibit axial growth of nanowires and enable them to achieve radial heterostructure growth.The phenomenon of crystal plane rotation occurs during radial heterostructure growth.Heterostructure growth will change in the volume of catalyst and the concentration of internal reactant atoms,leading to “concave” and “conical”.The growth of InAs and InP semiconductor nanowires grown on GaAs heterosubstrates and the growth of GaAs and GaP semiconductor nanowires on silicon heterosubstrates are also researched under the gold assisted catalyszed Vapor-Liquid-Solid mode.The larger lattice mismatch between InAs and GaAs makes the larger diameter InAs nanowire unable to grow on GaAs heterosubstrates,but accumulates near the GaAs substrate.The changes of growth conditions result some InP nanowires lateral growth on the GaAs heterosubstrates.The gold catalysts at the top of the nanowire decrease continuously,resulting in “conical” growth of GaAs nanowires.The sidewalls of GaP nanowire grown on silicon heterosubstrates are obviously "step",which are also caused by the instability of gold catalysts.In recent years,one dimensional semiconductor nanowires have attracted more and more attention due to their wide application prospects in the field of mechanics,electronics and optoelectronics.In this dissertation,a series of research work on III-V one dimensional semiconductor nanowires are carried out,which will provide theoretical basis and scientific basis in order to solve low integration and high power consumption in conventional material devices,realize the integration of high performance and low power devices,and develop micro-nano technology and information industry.Therefore,this dissertation has important research significance and value.