Synthesis And Optoelectronic Properties Of CdS/CdSSe Heterostructure Nanostructures

As the basic structural unit for integrated semiconductor electronic devices and circuits,one-dimensional semiconductor nanostructures are recognized as the basis of the next generation of nanoscale optoelectronic devices and integrated systems.Bandgap of semiconductor is one of the most important parameters in the field of photoelectron,which determines the absorption and emission characteristics of the semiconductor material.However,the natural the semiconductor bandgap is very limited,making a lot of inconvenience in device application.Therefore,adopting different composition contructures to achieve new bandgap becomes the dierect method,and the semiconductor energy-band engineering developed bandgap modulation.CdSxSe1-x is a kind of important alloy semiconductor material,the band gaps can be modulated in the range of 1.73 eV to 2.45 eV.Using the improved source mobile chemical vapor deposition method,we fabricated several new types of high quality CdSxSel-x nanobelts and nanowires successfully.Then we made corresponding research on the properties.The typical results are summarized as follows:(1)Using the source mobile chemical vapor deposition strategy,we prepared high quality alloy nanobelts--multilayer transverse heterostructure CdS/CdSSe/CdS/CdSSe/CdS by multistep reactions,so as to realize band gap mutations along width direction of the structure.Under the irradiation of 405 nm laser,the nanobelts present a type of glowing characteristic of green-red-green-red-green.Then,on the basis of the original experiment,we got the horizontal component of gradient CdSl-xSex nanobelts by changing moving speed of reaction source.Photoluminescence spectrum showed that these two kinds of special structure possess high crystallization properties,and show great application value for the photoelectric and low threshold lasers.(2)Through systematically modulating growing conditions,we achieved controllable axial CdS/CdSxSel-x single heterostructure nanowires.SEM showed these nanowires had smooth surface structure.The optical measurement results show that the prepared heterostructure nanowires have very good optical properties and crystallinity.Fluorescence microscopy images show that the nanowires are composed of CdS and CdSSe.The position related micro-photoluminescence spectra exhibit near band edge emission of CdS and CdSSe without obvious emission from defect states,which suggests that the wires have high crystalline quality.Optical waveguide study indicates asymmetric optical transmission characteristics in heterostructure.Further stimulation showed dual-color(red and green)lasing was realized based on these wires,with the lasing threshold of red light lasing lower than that of the green one.Theory simulation by COMSOL shows that the light can effectively propagate between CdS and CdSSe segments.Based on the special nanowire heterostructures,we fabricated nanowire heterojunction photodetector using electron beam lithography technology.Compared with the single-component CdS nanowire photodetector,CdS/CdSSe heterostructure detector has wider detection spectrum range,high switching ratio(105),high sensitivity(9.65 x 102 A/W),and high quantum efficiency(2.3×105%).