Preparation And Photoelectronic And Electrochemical Propertiesof Tungsten Disulfur Thin Film

Graphene-like transition metal chalcogenide compounds, such as MoS2, WS2, MoSe2, WSe2,have attracted wide interests because of their unique layer number-dependent of bandgap. The bulk material would transform from indirect to direct band gap when it becomes monolayer, which results in the compulsive photoelectronics properties. Therefore, it could be widely applied in the field of photoelectric sensor, thin-film solar cell, wearable device, semiconductor integrated circuit, and so on. Among these materials, WS2 two-dimensional atomic crystalswith few-layers have attracted a lot of attention because that intrinsic WS2 with a bipolar semiconductor show simultaneously n-type and p-type electronic transport properties. In this thesis, few-layers WS2 two-dimensional atomic crystals have been in-situ growth on tungsten foil. The main research works and results are as follows:(1) Few-layers WS2 two-dimensional atomic crystals have been prepared on tungsten foil by chemical vapor deposition. The results show that monolayer WS2 can be achieved at 700 oC for 1 min. Light absorption and photoluminescence confirm that the band gap of the pepared monolayer WS2 is around 2.08 eV. The constructed monolayer WS2 diode displayed excellent rectifying effect with the rectifying factor of 1.39. The photoactive devic also perfomed outsanding the photoelectric transformation efficiency of 7.12 mA/W.(2) Hydrogen evolution reaction capability of few-layers WS2 two-dimensional atomic crystals has been researched, and the results show that the few-layers WS2 achieved at 700 oC for 60 min showed the best hydrogen evolution reaction capability with the tafel slope of 82 mV/dec, and the current dencity reached to 10 mA/cm2 with overpotential of 0.36 V. The WS2 films with rough surface have been obtained by oxidation- sulfuration treatment of tungsten foil, and their current dencity reached to 10 mA/cm2 at overpotential of 0.37 V for the sample obtained at 750 oC for 30 min, and tafel slope of the sample is around 104 mV/dec.(3) Tungsten sulfide nanoribbons were obtained by bubble cutting in few-layers WS2, and their width was around 10 nm, and the length was around 100 nm-200 nm. Component analysis indicated that atomic ratio of S and W is 1:1. And the crystal structure analysis indicate that the tungsten sulfide nanoribbons belong to cubic crystal structure,and the interplanar spacing is 0.4 nm.