Controllable Growth And Electrical Properties Of Two-dimensional WS₂

With the development of semiconductor industry,the characteristic size of devices is decreasing,and the development of silicon-based materials according to Moore's law has encountered a bottleneck.The emergence of two-dimensional materials provides new opportunities for the development of semiconductor industry.As a typical two-dimensional material,tungsten disulfide(WS₂)has become a hot spot for its excellent electrical and optoelectronic properties.In order to expand the application of two-dimensional WS₂,the preparation of WS₂ films with high quality and large area becomes a prerequisite.In this paper,the following three studies have been carried out on WS₂:1.Research on large-area and high-quality controllable growth of CVD-WS₂.In this paper,WS₂ films were prepared by CVD method to investigate the effects of different process parameters(flow rate,the distance between source and substrate)during the growth of WS₂ films.By adjusting flow rate and distance,WS₂ films with different size and layers were obtained.Raman,PL,XRD,XPS,TEM and other characterization methods were used for systematically characterization analysis,and the growth law of WS₂ was obtained.2.Research on the growth mechanism of CVD-WS₂.A possible growth mechanism was proposed by combining the WS₂ films obtained under different conditions and their regularity.The layer numbers and size of the WS₂ films depend on the relationship between the mass transfer rate of the source and the chemical reaction rate of the film.When the present is larger than the latter,it is more inclined to nucleation,which leads to the dense nucleation point on the substrate;when they are basically matched,the film tends to grow laterally,which makes the transverse size of the film become larger,and the longitudinal growth of the film is inhibited,leading to controllable number of layers.3.Research on electrical properties of WS₂ films.In this paper,the field effect and energy storage characteristics of WS₂ were preliminarily explored by constructing the back-gated field-effect transistor and the supercapacitor electrode.CVD-grown two-dimensional WS₂ exhibits n-type characteristics.The average electron mobility of monolayer WS₂ thin films is 1.5 cm²v^-1s^-1 with an I_on/off ratio of 10⁵ and a bilayer WS₂thin film with an average electron mobility of 13 cm²v^-1s^-1 with an I_on/off ratio of 10⁶.As electrode materials for supercapacitors,the electrodes of the few-layer structure have a specific capacitance of 1633 F/g at current densities of 1 A/g,with a rate performance of only 74.7%.However,the electrodes of the multilayer structure have a specific capacitance of 169 F/g at current densities of 1 A/g,with a rate of 85%.Our results may offer insight on the potential applications of WS₂ thin films in wide range of fields.