Synthesis And Characterizaiton Of Pure And Doped ZnS Materials By Chemical Vapor Deposition At Low-temperature

ZnS is one of the most important Ⅱ-Ⅵ semiconductor materials, with the direct wide band gap of3.7ev. Due to ZnS materials’excellent photoelectric property, it has been widely used in optoelectronics applications, such as lasers, field emitters, sensors and light-emitting diodes. Doped ZnS materials have wider range of emitted wavelengths and higher photoluminescence efficiency, being used as fluorescent powders. Because ZnS micro-nano materials have many new properties, they become the focus of the current study.At the present, most methods of synthesizing undoped and doped ZnS micro-nano structures are evaporating ZnS powder at high temperatures. Because ZnS has a highest melting point (1700℃), this method needs high work temperature (about1000℃), so it is hard to control the temperatures. How to synthesize undoped and doped ZnS micro-nano structures at lower temperature has become a hot focus. Because Zn powder and S powder have lower melting points (419℃and119℃), they can be used as source materials to synthesize undoped and doped ZnS micro-nano structures. In this study, ZnS nano-particles, ZnS micro-nano spheres, ZnS nanowire, Mn2+-doped ZnS nanowire, Ga-doped ZnS nanowire and Ga-doped ZnS nanorods were synthesized by chemical vapor deposition at low temperatures, using Zn powder and S powder as source materials. The structure, composition, morphology and luminescent properties of undoped and doped ZnS micro-nano structures were analyzed respectively. The main results were as follows:1、ZnS nano-particles and micro-nano spheres were synthesized on Si (100) substrate without Au and with Au nano-particles by chemical vapor deposition at low temperatures. ZnS nano-particles’growth is controlled by VS mechanism, but micro-nano spheres’growth didn’t follow VLS mechanism. The possible growth mechanism of ZnS micro-nano spheres was discussed, and the conclusion is that:the eutectic point of Au/Si/Zn/S nano droplets may be higher than450℃, so Au/Si/Zn/S nano droplets are solidified as Au/Si/Zn/S nano particles, being the nucleus of ZnS micro-nano spheres; ZnS micro-nano spheres, nanorods, nanowires were synthesized at the temperatures of450℃,550℃and650℃respectively. ZnS nanorods and nanowires’growths are controlled by VLS mechanism. All samples show larger near-band-edge UV emission peak of336nm, and with the increase of temperatures, the intensity of PL is increasing; ZnS worm-like nanowires, smooth nanowires and nanowires with a lot of micro slices were synthesized at the Ar flows of60sccm,80sccm and100sccm. All samples show larger near-band-edge UV emission peak of336nm, and with the increase of Ar flows, the intensity of PL is increasing at the same time. In the Ultra-visible spectra of ZnS samples at different Ar flows, ZnS samples have very strong absorption intensity of UV-light between250nm and350nm, and with the increase of Ar flows, the intensity of Ultra-visible spectra is increasing.2、Mn2+-doped ZnS nanowire, Ga-doped ZnS nanowire and nanorods were synthesized by chemical vapor deposition at low temperatures. Mn2+-doped ZnS nanowire emits a relatively weak red emission band centering at about587nm, being controlled by VLS mechanism. With the increase of the temperatures, the morphologies of Ga-doped ZnS evolve from worm-like nanowires to smooth nanowires and then to nanorods. All samples show larger near-band-edge UV emission peak of336nm and a weak red light emission peak of675nm, nevertheless, all other emission peaks are caused by defects of Ga doping. Ga-doped ZnS nanowire and nanorods are controlled by VLS mechanism.