Photonic Properties Regulation Of Tellurium Doped And Surface Oxidated CdS Micro-nanostructures

As an important member of II-VI semiconductor group,cadmium sulfide(CdS)with band gap of 2.42 eV at room temperature is an excellent candidate to investigate the light-matter interaction.In addition,CdS shows good stability,high luminescence efficiency and high electron mobility that may find important application in laser,transistor,light-emitting diode,non-linear optical devices,solar cells.Doping is one of the powerful technology to change the lattice structure and electronic band structure of micro-nano materials,which can effectively control and optimize the electronic,photonic and photoelectric properties.In order to improve the optical properties of CdS micro-nanostructures,this master's thesis focuses on the synthesis and photonics properties investigation of doped and oxidized CdS micro-nanostructures.The corresponding photo-physics process was explored.The main work of this paper includes the following two aspects:(1)Te-doped CdS nanowires with high quality were prepared by a simple two-step chemical vapor deposition(CVD)method.By means of X-ray diffraction(XRD),scanning electron microscopy(SEM),X-ray energy dispersive spectroscopy(EDS)and Raman spectroscopy,it is proved that the prepared Te-doped CdS nanowires show high quality wurtzite structure.Te element is uniformly doped on the nanowires while without changing the lattice structure of CdS.The effects of Te doping on the luminescent properties of CdS nanowires were studied.It is confirmed that the luminescence performance of CdS nanowires is greatly weakened with disappear WGM cavity mode luminescence under heavy doping.The Te-doped CdS nanowires demonstrate strong electron-phonon coupling and strong surface polaron,confirmed by temperature dependent Raman spectroscopy.The luminescence of Te-doped CdS nanowires is modulated by both surface polaron and WGM mode microcavity.The response of surface polarization to temperature is obvious and the modulation of surface polarization at low temperature(80K)is weakened greatly.This Te-doped CdS also shows a wide absorption from ultraviolet to red light range.(2)Pure CdS nanowires were heated to 475 ~oC under air condition to achieve the oxidized surface.By XRD,SEM,EDS,Raman spectroscopy and PL mapping characterization,it is proved that the as-prepared samples are surface-oxidized CdS nanowires with high quality wurtzite structure.The luminescence mechanism was studied by steady PL spectroscopy and time-resolved PL measurements under different conditions.Surface oxidation not only improves the luminescent properties of CdS nanowires(wide luminescent band,high luminescent efficiency),but also realizes the controllable luminescence coupling between the WGM microcavity and the exciton polaritons.Our results also demonstrate that the short-wave luminescence is mainly controlled by exciton polaritons while WGM optical microcavity plays an important role on the long-wave luminescence.