Preparation And Photoelectric Properties Of Two-dimensional Layered Material MoS₂

As a representative of two-dimensional layered nanomaterials, graphene has been studied intensively. Recently, the research on graphene-like two-dimensional layered materials such as transition metal sulfides （MoS₂ as a typical example）, have been in the research highlight. Given the special band structure of MoS₂, it has a relatively significant applications in energy, optoelectronic devices, etc. In this thesis, preparation and optoelectronic property studies of MoS₂ expand mainly in the following five parts.（1） In Chapter One, we summarized the development and application of the two dimensional layered nanomaterials, the terahertz time-domain spectroscopy system and the spectroscopic ellipsometry system. Starting from the development history and research status of two dimensional layered nanomaterials, we first discuss the limitation of graphene as the optoelectronic devices and then discuss the structure and properties of MoS₂,（2） In Chapter Two, we studied the dielectric response of bulk MoS₂ crystal in terahertz （THz） and visible region. As the working frequency of many optoelectronic devices climbs from the GHz to THz region and the demand of optoelectronic devices in vsible region increases, we analyzed and discussed the dielectric response of bulk MoS₂ crystal in THz and visible region in detail with THz time-domain spectroscopy system and spectroscopic ellipsometry system, and calculated the absorption coefficient, the refractive index, and so on. What’s more, we used Lorentz and Drude model fitting to explain the physical mechanism behind the response. Relevant research can further promote the application of optoelectronic device based on THz and visible of MoS₂.（3） In Chapter Three, we discussed various preparation methods for monolayer MoS₂. In order to study preparation method of monolayer MoS₂, we tried Scotch tape mechanical exfoliation, physical vapor deposition, and liquid-phase exfoliation to prepare monolayer MoS₂. We used the optical microscope, Raman spectroscopy and scanning electron microscope（SEM）, and so on, to explore the quality of sample prepared by various methods. By adjusting and optimizing experimental parameters constantly, we obtained the method of preparing large area and high-quality monolayer MoS₂.（3） In Chapter Three, we discussed various preparation methods for monolayer MoS₂. In order to study preparation method of monolayer MoS₂, we tried Scotch tape mechanical exfoliation, physical vapor deposition, and liquid-phase exfoliation to prepare monolayer MoS₂. We used the optical microscope, Raman spectroscopy and scanning electron microscope（SEM）, and so on, to explore the quality of sample prepared by various methods. By adjusting and optimizing experimental parameters constantly, we obtained the method of preparing large area and high-quality monolayer MoS₂.（4） As we know from the band structure of MoS₂, the thin layer MoS₂ has different optoelectronic properties compared with bulk MoS₂ crystal And thin layer MoS₂ is applied to optoelectronic device generally. In Chapter Four, we analyzed the THz response of MoS₂ films with different thicknesses prepared by liquid-phase exfoliation with THz time-domain spectroscopy system, and calculated the thin layer of MoS₂ conductivity in THz region.（5） In Chapter Five, we studied the photoelectrochemical properties of MoS₂ film from photo electrochemical response theory of semiconductor photoelectrodes. We analyzed and discussed the preparation of photoelectrodes based on MoS₂ film, measurement of photocurrent and physical mechanism of MoS₂ photoelectrochemical response. Furthermore, we proposed research ideas to enhance the photoelectrochemical response of MoS₂ film.