Polarization Photodetector Based On Two-Dimensional Molybdenum Ditelluride

Photodetectors play an important role in people's daily life,especially in the fields of optoelectronic displays,imaging,information transmission,environmental monitoring,biomedicine,and military.Most of the light in nature is polarized light formed after a series of reflection,refraction and scattering.With the increasing requirement for quality of life,common photodetectors have been unable to meet the needs of people.Using the polarization information of light,polarization detector can expand the dimension of information and detect the information that cannot be detected by common detectors.In recent years,two-dimensional materials have attracted people's attention due to their unique optical and electronic properties,especially the transition metal dichalcogenides.They have a wide band gap,which makes them ideal materials in the field of photodetectors from visible light to infrared light.Among them,molybdenum ditelluride can exist in two stable states,one is semiconductor state,the other is semi-metal state,and the two states can be converted to each other under certain conditions.At the same time,molybdenum ditelluride also has a very small band gap of 1 e V,and can be converted from an indirect band gap to a direct band gap,making it possible to detect longer wavelength light and have higher detection efficiency.However,due to the symmetry of its lattice structure,molybdenum ditelluride does not have light polarization characteristics.Therefore,it is of great significance to realize the polarization detection of molybdenum telluride by strain.In this thesis,a wrinkled molybdenum ditelluride photodetector on a polydimethylsiloxane substrate is realized based on strain engineering.Experimental results show that the detector has obvious light polarization characteristics.Finally,based on the method of periodical structureinduced material strain,combined with surface plasmons' enhanced absorption of light,a silicon-based molybdenum ditelluride polarization photodetector was simulated.And simulation results show that this structure has obvious light polarization characteristics.This thesis mainly discusses:(1)The physical mechanism of the photodetector,the structure and properties of molybdenum ditelluride,strain engineering,and experimental schemes of wrinkled molybdenum ditelluride.(2)Preparation of wrinkled molybdenum ditelluride photodetector and its photoelectric properties.Including the preparation of materials,exploring the influence of metal electrodes on the realization of wrinkled molybdenum ditelluride detectors,testing the photoelectric properties of silicon-based and polydimethylsiloxane-based photodetectors,etc.Finally,a molybdenum ditelluride polarization photodetector was realized on a polydimethylsiloxane substrate.(3)The optical simulation of a silicon-based molybdenum ditelluride polarization photodetector was initially completed by using a silicon-based periodic structure to induce material strain and combining surface plasmons to enhance light absorption.