Fabrication Of Cadmium Selenide-gold Composite Structures By Physical Vapor Deposition And Their Long-range Luminescence Properties

Reasearchers have paid much attention to semiconductor luminescent materials due to their significant advantages such as adjustable bandgap,diversified material composition and potential applications in the field of optical sensing and detection.II-VI semiconductor luminescent materials(such as CdS,CdSe,etc.)are most widely used in practical applications because of their large absorption cross sections,long exciton lifetime,fast carrier transportation and radiation decay rate.As a photoluminescent material,it is of extremely high research value due to its excellent characteristics.In the field of photoluminescence,remote illuminating should gain more attention because it can significantly reduce the interference caused by the background during the actual operation,moreover,it can also reduce the damage caused by high energy of the excitation light onto the detection target.The one-dimensional nanomaterial with large aspect ratio can be used as a nano-waveguide for photoluminescence propagation,so it is considered to be an excellent choice for remote illumination,sensing and detection.During the research,it was found that the surface plasmon resonance effect of precious metals can enhance the local electromagnetic field around the material,which makes the material produce strong luminescence at lower excitation energy.This phenomenon has gained the interest of researchers.However,there is little research on the long-range luminescence properties of one-dimensional semiconductor photoluminescent materials,and the luminescence intensity of one-dimensional nano-materials is still weak,which cannot meet the needs of practical applications.Therefore,it is necessary to improve the long-term luminescence properties of one-dimensional semiconductor photoluminescent materials.In this paper,the effects of polarization direction,surface plasmon resonance effect of noble metal and photoluminescence quenching effect on the photoluminescence properties of nanowires are studied.And the experimental methods of one-dimensional luminescent materials with higher luminescence intensity are discussed in detail.The contents of our research are summarized as follows:(1)Using CdSe powder as raw material,CdSe nanowires were prepared by physical vapor deposition method,and the photoluminescence properties of as-prepared samples were studied.The product is obtained by precisely controlling the reaction time,the reaction temperature and the carrier gas flow rate.The synthesized sample with uniform morphology and few surface defects owned a length of several micrometers and a diameter of 300 to 500 nm.The photoluminescence properties of the materials were studied by conjugated Raman system and FDTD simulations.The results show that the different excitation energy and polarization direction have great influence on the remote luminescence properties of CdSe nanowires.(2)CdSe-Au composites were prepared by physical vapor deposition using CdSe powder and Au powder as the raw materials,and their photoluminescence properties were studied.The materials were grown based on the VLS mechanism.During the growth process,the Au particles with lower melting point are melted to form Au droplets firstly.With the Au droplets act both as the structure directing agent and the morphology control agent,the CdSe nanowires are directed to grow directionally.When the reaction is completed,the temperature is lowered.At room temperature,the Au particles would stay on the top of the CdSe nanowire to form a CdSe-Au composite structure.The synthesized material has a good crystal form,uniform morphology and smooth surface.The photoluminescence properties and FDTD simulations of the composite structure show that the remote luminescence and in-situ luminescence of the composites are quite different.Compared with pure CdSe nanowires,the presence of Au particles greatly reduces the luminescence intensity when the composite is illuminated in situ.For remote illumination,when the excitation source is at the CdSe end,the luminescence intensity reaches a maximum value;when the excitation source is at the Au end,the luminescence intensity is significantly weakened.In addition,when the excitation light energy becomes higher,the angle between the polarization direction and the nanowire becomes smaller,the luminescence intensity becomes higher.