The Controllable Synthesis And Photoelectric Properties Of Two-dimensional Graphene-like Materials

Since the finding and development of graphene, more and more people pay attention to the graphene-like materials. Among the family of graphene-like materials,transition metal dichalcogenides are becoming the hot materials with the adjustable band-gap structures, excellent photoelectronic properties, high carrier mobility and the high ratio of switching current. The topological insulator behaves as insulator in the bulk but has conducting surface state on the surface protected by time-reversal symmetry, which results from the strong spin orbital coupling. The exploration and development of topological insulators will promote the development of the computer filed. In this thesis, we studied the preparation and characterization of two-dimensional transition metal dichalcogenides and topological insulators. We also investigated the surface potentials of transition metal dichalcogenides and photoresponse properties of as prepared topological insulator nanoplates. The main contents are as follows:1. The two-dimensional transition metal dichalcogenide nanoplates and large size nanofilms(WS2 、 WSe2) were synthesized on different substrates(SiO2/Si and sapphire) by thermal evaporation method. The results indicated that the transition metal dichalcogenides were easier to grow excellent two-dimensional nanostructures on the sapphire substrates, which had many platforms on the surface. As-prepared nanostructures of transition metal dichalcogenides had large size up to micrometer even centimeter. Meanwhile, we also investigated the mechanism of the growth and evolution of two-dimensional transition metal dichalcogenide nanostructures. The nanostructures of transition metal dichalcogenides were characterized by Kelvin probe force microscopy, Raman spectroscopy and scanning electron microscopy. As new two-dimensional semiconductors, transition metal dichalcogenides have potential applications in optoelectronic devices. We have performed surface potential measurements and photoluminescence properties of the transition metal dichalcogenides nanostructures. We also attempted to explain the results, which appeared in the measurements.2. Topological insulators nanoplates were prepared by thermal evaporation method. The corresponding photoelectrochemical tests were carried out by using a typical three-electrode electrochemical cell configuration. Comparing thephotoresponse properties of the Bi2Se3 nanoplates and Bi2Se3 bulk, Bi2Se3 nanoplates exhibited better conductivity, larger photocurrent and more stabilized continuous cycling under a simulated sunlight source. We also studied the photoresponse properties of the Bi2Se3 nanoplates under different wavelength light sources. The results indicated that the Bi2Se3 nanoplates had highest sensitivity and the smallest dark current with the wavelength of light source 455 nm and 655 nm respectively. At the same time, we also studied the photoresponse properties of Bi2Te3 nanoplates. Our experimental results indicated that two-dimensional topological insulator nanoplates have promising applications in photoelectric sensor field.