Research Mn- Dimensional Superlattice Material Preparation And Optical Properties: ZnS

As an important wide band-gap semiconductor compound of the IIB-VI groups, Zinc sulfide has been well-known for its photoluminescence and electroluminescence, which enable wide applications in the fields of Ultraviolet-Light Sensors, Photodetector and Solar cell. In this paper, we explore the preparation conditions of ZnS one-dimensional nanostructures, and then successfully prepared the (3C-ZnS)n/(2H-ZnS)m superlattice structures in Mn-doped ZnS by a chemical vapor transport method. The discussions are presented as follows.Syntheses of the one-dimensional and platelike wurtzite ZnS nanostructures have been achieved by the thermal evaporation of ZnS powder. The role of the substrate temperature and Au catalyst in defining the morphology of the ZnS nanostructures has been found. The nanowires and nanoribbons were synthesized onto the Si substrate in the presence of the Au catalyst, and the platelike ZnS nanostructures were produced onto Au-uncoated Si substrate. The morphological change of the nanostructures was studied through scanning electron microscope. Room temperature photoluminescence measurements with325nm excitation showed three emission bands located at345nm,395nm and460nm, respectively.In this paper, microsaws and microtowers have been prepared by vapor-liquid-solid (VLS) and vapor-solid (VS) method which is based on thermal evaporation, respectively. The role of the Au catalyst in defining the morphology of the ZnS microstructures has been found. The microsaws were synthesized onto the sapphire substrate in the presence of the Au catalyst, and the microtowers were produced onto Au-uncoated sapphire substrate. The microstructure changes were studied through scanning electron microscope. The structural characterization of the microstructures was indicated by X-ray diffraction and high-resolution transmission electron microscope. Room temperature photoluminescence measurements with325nm excitation showed four emission bands located at～400nm,～480nm,～520nm and～580nm, respectively.In this paper, we report the first successful growth of (3C-ZnS)n/(2H-ZnS)m superlattice structures in Mn-doped ZnS nanoribbons prepared on Au-coated Si substrates by a chemical vapor transport method. The lattice resolved HRTEM image presents the self-assembled (111)(3C-ZnS)/(100)(2H-ZnS) superlattices, where both the (3C-ZnS) ZnS atom layer and the (2H-ZnS) atom layer alternately arrayed in the plane of nanoribbons along the axis growth direction. The individual Mn-doped ZnS nanoribbons, with uniform widths ranging from100to800nm and lengths ranging from tens to one hundred micrometers, are composed of the hexagonal wurtzite atom layers growing along [100] axis direction and [001] vertical direction and the zinc blende atom layers growing along<111> direction. An identical strong photoluminescence transition peak at580nm was observed for all ZnS:Mn samples, and the peak intensity reaches to a maximum with Mn content of0.68at.%from the EDX analysis in2at.%Mn-doped ZnS samples.