Synthesis And Characterization Of ZnSe Based Nanowire Heterostructures

In recent years,one dimensional semiconductor heterostructures have become research hot point of nano materials science.One dimensional semiconductor heterostructures not only shows the property of homogeneous nanowires but also gains many new properties,for example,heterostructures ofâ…¡-â…¥/â…£group assemble the excellent optical performance ofâ…¡-â…¥group and the mature technology ofâ…£group semiconductors,so they play an important role in "tailor" homogeneous physical property of semiconductor nanowires,also have potential application in many fields.In this dissertation,we mainly focus the fabrication and characterization of ZnSe based nanowire heterostructures.The results are introduced as following:1.Ge nanosheets decorated hierarchical ZnSe/GeSe nanowire heterostructures were synthesized via simple CVD method with ZnSe and Ge powder.XRD patterns reveal it was composed of ZnSe,Ge and GeSe,while SEM images show that most as-grown product is nanowire with branches on both sides,only a little is nano trace of ZnSe/GeSe biaxial nanowires.According to HRTEM and SAED images,a relatively clean interface between ZnSe and GeSe was observed,and Ge nanosheets with diameter of almost 50nm uniformly distributed on the nanobranches.The novel ZnSe/GeSe nanowire heterostructures are grown via co-growth vapor transfer mechanism.Raman spectrum at room temperature reveals the classical Raman peaks of ZnSe,Ge and GeSe,and all of them have a little blue shift and width change.2.Ge/GeSe biaxial nanowire heterostructures(sample 1) and ZnSe/Ge core-shell nanowire heterostructures(sample 2) were synthesized by controlling the relative quantity ratio of ZnSe and Ge powder via CVD method.For smaple 1, XRD patterns show it was composed of cubic Ge and orthogonal GeSe,while SEM images reveal that most nanowires with uniform size were grown on the Au coated Si substrate.According to the images of HRTEM and SAED, Ge/GeSe biaxial nanowire heterostructures have a diameter within 100nm,and the diameters of Ge and GeSe sub-nanowires are 20-50nm and 30-70nm, respectively.The nanowires are grown via VLS mechanism.Ge and GeSe Raman peaks could be observed,and all of these peaks had a little red shift as for the nano size effect.While for sample 2,the as-grown nanowires are composed of cubic ZnSe and cubic Ge according to XRD patterns,while SEM images show their core-shell structures,and only a few of them are not core-shell structure.This kind of nanowires is also grown via VLS mechanism.3.CdS/SiO₂ core-shell nanowires are synthesized successfully via CVD method. XRD patterns show the as-grown product was hexagonal CdS.All the diffraction peaks of CdS are strong and narrow,reveal their excellent crystallinity.SEM images show that the product are comb-like nanowires,up to tens of micrometers with diameters less than 500nm,every comb tooth is several nanometers in lengh,and the surface of the nanowires is smooth enough. TEM and HRTEM images show the CdS core/SiO₂ shell structure of the nanowires,and SAED patterns show CdS grew along the direction of {1011}. This kind of nanowires is also grown via VLS mechanism.Raman spectrum at room temperature reveals 1LO and 2LO optical photon mode and the photon scattering peaks of CdS.