Study Of Two-dimensional Telluride-based Materials:Controllable Synthesis,Properties And Device Construction

The discovery of graphene opens the door to the research of two-dimensional materials.As a class of ultra-thin channel materials,two-dimensional materials are expected to achieve high integration density nano devices due to their unique flexibility,anisotropy,low-temperature manufacturing,and integration convenience.Tellurium is a single-element semiconductor,which has been used in thin film transistors as early as the 1960s.However,the application of tellurium in other fields is rare.The development of two-dimensional materials has rekindled the upsurge in the controllable preparation and physical properties of tellurium and its tellurides.Two-dimensional tellurium and tellurides prepared by liquid phase exfoliation,chemical vapor deposition,and molecular beam epitaxy have performed well in optical,electrical,and magnetic applications.However,it is not easy to prepare large-area high-quality tellurium.The reported methods for preparing tellurium and tellurides are complicated,expensive equipment,and long production cycle limit the large-scale and large-area production of tellurium.On the other hand,there are many types of tellurides which have multi-phase structure,thus resulting of many gaps in the controllable preparation and physical properties of two-dimensional telluride systems.In this paper,the controllable preparation of tellurium and telluride is achieved through the innovation of preparation methods.The physical properties of two-dimensional tellurium and telluride in terms of light and electricity are mainly studied.Finally,the application of materials is expanded by designing two-dimensional devices.The main work content of this paper is as follows:First,a two-step method is used to realize the controllable preparation of large-area tellurium thin films.The film deposition rate can be stabilized at 0.01 nm/s,the deposition area is larger than centimeters,and the surface roughness is only 1.6 nm.The optical absorption of tellurium thin films with different thicknesses has been tested systematically.The optical absorption rate of thin films with a thickness of more than 20 nm is more than 30%in the visible light range and more than 15%in the communication band.The electrical transport properties of thin films are studied through the construction of Hall devices,and the electrical properties of tellurium thin films with different thicknesses are obtained,including Hall mobility,carrier concentration,resistivity,Hall coefficient,etc.Finally,the application of thin films is expanded,and the storage and memory properties of two-terminal devices are studied,as well as the electrical storage and photoelectric combination functions of three-terminal devices.The switching ratio of three-terminal devices can reach 100,000.Heterojunction based on tellurium thin film and silicon are designed to study the photoelectric properties of the heterojunction,which also realize self-driven detection from visible to near infrared,but the specific detection rate of heterojunction formed by 2 nm tellurium thin film and silicon under 1550 nm@1.511 m W/cm²illumination is only 3.25×10⁵ Jones.In order to further improve the optoelectronic performance of the material,the synthesis of two-dimensionalα-phase manganese telluride（α-MnTe）nanosheets is realized for the first time on a mica substrate by chemical vapor deposition,and the synthesis of this uncommon telluride at the nanometer scale is explored for the first time.Electrical and optoelectronic properties.The precise control of the size of theα-MnTe nanosheets is achieved by adjusting parameters such as gas flow,temperature,and reactant concentration during the reaction,and a series of characterizations proved the high quality of the nanosheets.The electrical properties ofα-MnTe are studied through temperature-variable resistance tests and the construction of transistors,which prove the conductive behavior of nanosheet p-type semiconductors.Finally,the photoelectric properties ofα-MnTe nanosheets are explored,and the specific detectivity in the visible light range of 400 nm@0.062 m W/cm² is as high as 3.32×10¹² Jones.Finally,high-quality two-dimensional type II Weyl semimetal WTe₂ crystals are prepared by iodine trichloride-assisted chemical vapor transport method.The crystal size can reach centimeter level,and the controllable preparation of nanosheets with different thicknesses can be achieved by mechanical exfoliation.The resistance changes of nanosheets at different temperatures and different magnetic fields are systematically studied through Hall devices,and the magnetoresistance and electrical transport parameters of nanosheets at different temperatures are obtained.Finally,the optoelectronic properties of nanosheets with different thicknesses are tested by constructing optoelectronic devices,and provided a route for the future photoresponse testing based on semi-metallic materials.