Preparation Of Tungsten Diselenide Via Thermal Deposition And Its Application

Two-dimensional transition metal sulfur compounds(TMDCs)possess broad application prospects in the field of optoelectronic devices,sensing and energy transformation,e.t.,among which tungsten disulfide,the representative semiconductor material,which has excellent optoelectronic properties and unique mechanical property,can be employed to prepare the flexible wearable devices.However,the uncontrollable thickness and small film-forming area of the preparation process will limit the preparation,film-forming area and film-forming continuity of single-layer WSe₂.Although there are many methods such as mechanical stripping,hydrothermal synthesis,chemical stripping and laser pulse deposition,these methods generally have limitations such as high operating cost and low energy production.In this thesis,two methods of preparing WSe₂ thin films are proposed,and the electrical and optoelectronic properties of WSe₂ based devices are analyzed and studied by using the prepared large domain monolayer WSe₂ thin films in field-effect transistors,piezoelectric sensors combined with PVDF and photodetectors.Firstly,the preparation of large-area whole film and single crystal tungsten selenide materials and the application of photoelectric devices were explored.The wafer-level monolayer WSe₂ films with a size of 6-inch were successfully synthesized by the metal post-senlenization method.The electrical properties of the field effect transistor were further investigated.The electrical properties of the field effect transistor are studied.The electron mobility of the field effect transistor was 292 cm² V^-1 s^-1.The field effect transistor was constructed from the selenized tungsten diselenide film,and the pressure sensing system was integrated with the PVDF piezoelectric sensor.The piezoelectric signal of the integrated device was tested by the weight gravity pressure system and the motor driven pressure system.The piezoelectric signal increased linearly with the increase of pressure.The photoelectric response of the piezoelectric signal is 2.29×10² A W^-1 and the detection rate is 1.05×10¹²Jones.Second,after seed-crystal embedding by tungsten oxide and chemical vapor deposition,large domain monolayer single crystal tungsten selenide is prepared.The field effect transistor was constructed by the preparation of tungsten diselenide thin film with the switching ratio of10⁷.The photosensitivity of the device is studied,when the light power density is as low as1.59 W?m^-2,there is still a large photocurrent response of 0.264?A.The purpose of this paper is to study the shortcomings of the synthesis method of large area WSe₂ at the present stage,to promote the simple and efficient preparation of large area WSe₂ in thin layer,and realize the preparation of WSe₂ on different substrates.The research of this thesis contributes to the promotion of the application of 2D materials in the field of optoelectronics and piezoelectricity.