Preparation Of Black Phosphorus Thin Films And Its Application In Devices

Two-dimensional(2D)material is a material composed of a single atomic layer or several atomic layers,which has been widely and deeply studied in the semiconductor field because of its low-dimensional effect.Black phosphorus is a new and emerging 2D semiconductor material similar to graphene.Different from the zero band gap characteristic of graphene,black phosphorus has a direct band gap continuously adjustable with the number of layers,and the band gap covers the broadband from visible to near-infrared band.Moreover,black phosphorus also has high carrier mobility and large in-plane anisotropy.In summary,black phosphorus has excellent optical and electrical properties and has a promising application in semiconductor devices.In this thesis,we study the preparation and characterization of2 D black phosphorus materials and black phosphorus thin films firstly,and then fabricate black phosphorus thin films field effect transistor,and explore the electrical properties of the device by testing and analyzing their transfer and output characteristic curves.The main contents of this thesis are as follows:To start with,the concept of 2D materials and the development of 2D semiconductor materials have been introduced.Through the transverse comparison about the photoelectric properties of typical 2D semiconductor materials,the significance of choosing black phosphorus as the object of study has been clarified,and the crystal structure of black phosphorus and its applications in semiconductor devices have been briefly introduced.Then through the detailed introduction of various preparation methods and characterization methods of common 2D semiconductor materials,it provides a useful experimental design idea for the preparation and characterization of 2D black phosphorus materials in this work.In this thesis,2D black phosphorus materials have been prepared by ultrasonic assisted liquid exfoliation method.The micro-structure and material properties of 2D black phosphorus have been characterized and analyzed by such as Opticalmicroscope(OM),X-ray diffraction(XRD),Transmission electron microscope(TEM),Scanning electron microscope(SEM),Atomic force microscope(AFM),Raman spectra and Ultraviolet-visible absorption spectrum.Furthermore,the effects of different liquid phase stripping media,ultrasonic time,ultrasonic frequency and centrifugal speed on the size and morphology of black phosphorus have been investigated.Finally,the optimal preparation conditions for the 2D black phosphorus materials have been obtained.Furthermore,black phosphorus thin films field effect transistor has been fabricated by solution dropping casting.First of all,the influence of annealing temperature on the surface morphology of black phosphorus thin films has been investigated,and it was found that the surface roughness of the black phosphorus thin films was the lowest and the films quality was higher when the films are annealed in vacuum at 50 ? for 2 h.Then the transfer and output characteristic curves of the device have been tested and analyzed.It is found that the black phosphorus thin films field effect transistor prepared in this work shows typical p-type field effect characteristics,and various electrical properties are excellent.Finally,a feasible method for optimizing the preparation process of black phosphorus thin films and device structure parameters has been proposed,which provides a new idea for the further research of the application and development of black phosphorus thin film materials in semiconductor devices.