Synthesis And Characterization Of ZnSe/Ge Nanowires Heterostructures

Recently,one-dimensional(1D) heterostructure nanomaterials have been received considerable attentions because these nanomaterials have novel physical and chemical properties compared with their bulk counterparts,which have shown the potential applications.In this dissertation,we report synthesis of 1D heterostructures materials semiconductors,such as ZnSe/Ge nanowire heterostructures,Cd₄SiS₆/SiO₂ hierartcal heterostructure nanowires and SiO₂ net-like nanobelts by Chemical Vapor Deposition (CVD) method.The control of morphology and their properties were investigated. The significant results are introduced as following:1.Single-crystalline ZnSe/Ge nanowires were grown on Si substrate via a simple one-step thermal evaporation of mixed ZnSe and Ge powders.Measure result indicates that the ZnSe/Ge nanowires heterostructures has a uniform diameter with 200nm and length with several micrometers.Subnanowires of ZnSe and Ge,with ideal interfaces along the growth orientation,has a diameter of 120 and 80 nm respectively,and they are single crystalline.The experimental evidence suggests that the biaxial nanowires are formed via a co-growth mechanism.The vibrational property of ZnSe/Ge nanowires was investigated by Raman spectrum at room-temperature.And the heterostructure may be have some new optical properties with the ideal interface.2.Novel hierarchical Cd₄SiS₆/SiO₂ based heterostructure nanowire arrays were fabricated on silicon substrates via CVD method.The as-grown products were characterized using scanning electron microscopy,X-ray diffraction,and transmission electron microscopy.Studies reveal that a typical hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire is composed of a single crystalline Cd₄SiS₆ nanowire core with amorphous SiO₂ sheath.Furthermore,secondary nanostructures of SiO₂ nanowires are highly dense grown on the primary Cd₄SiS₆ core-SiO₂ sheath nanowires and formed hierarchical Cd₄SiS₆/SiO₂ based heterostructure nanowire arrays which stand vertically on silicon substrates.The possible growth mechanism of hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire arrays is proposed.The optical properties of hierarchical Cd₄SiS₆/SiO₂ heterostructure nanowire arrays are investigated using Raman and Photoluminescence spectroscopy.The Raman peaks can be assigned to the modes of Cd-S and Si-S.In PL spectra,the peak at 483 nm can be identified as the near-band-edge emission of Cd₄SiS₆ cores.3.The novel SiO₂ net-like nanobelts have been successfully fabricated on Au-coated Si substrates by a simple CVD method.The as-synthesized SiO₂ nanostructures were characterized by using scanning electron microscope(SEM), transmission electron microscope(TEM) and energy dispersive spectroscopy(EDS), respectively.The results show that the as-grown SiO₂ net-like nanobelts are rather uniformly and each nanobelt is about hundreds of micrometers in length and about 1-2 micrometers in width.We operated series of experiments by changing the parameters and indicate the growth rule of different morphology.The important role of CdS in the formation of the SiO₂ net-like nanobelts and the possible growth mechanism of the as-grown nanobelts from the thermodynamic aspect are discussed.