Preparation Of Rhenium-based Transition Metal Chalcogenide Alloy And Its Photoelectric Properties

Two-dimensional transition metal chalcogenides?2D TMDs?have drawn much attention in many basic research fields such as electronics,optoelectronics,and catalysis for their excellent physical and chemical properties.Semiconductor materials in TMDs show the advantages of direct bandgap transition,high mobility of carrier,and high switching ratio in the field of microelectronic devices due to the effect of quantum confinement.In order to be applied in optoelectronics field better,to develop the full potential of these 2D semiconductor materials,precise control of their bandgap and electronic characteristics are required.In recent years,researchers have tried to synthesize alloys by doping heteroatoms in the lattice of 2D semiconductor materials,in order to realize the regulation of the bandgap and electrical properties of them to meet the needs of modern electronic devices.In particular,researchers have alloyed 2D TMDs materials with different properties in recent years,synthesized a series of new 2D semiconductor alloy materials,and found a series of excellent physical and chemical properties.However,most of the researches on 2D alloys are only in the same phase materials.After the alloying of these same phase materials,the regulation of many properties are limited to a certain range,and the breakthrough of properties cannot be achieved.In view of the fact that 2D TMDs have different phase structures,the introduction of the phase structure variable in 2D TMDs alloys will add a new degree of freedom to the structure and properties of alloys.In this work,phase-tunable 2D Mo_xRe_1-xS₂ alloys with different component are synthesized.First,it was found that a higher growth temperature was beneficial to the alloying process of two materials with different phases by exploring the regulation of growth temperature,and the production of high-quality 2D Mo_xRe_1-xS₂ alloys was achieved in the end.Then,the composition,phase structure,bandgap,and electrical properties of the obtained alloy samples were studied in depth,and their internal relations were revealed,and controllable modulation of their phase structure,bandgap,and electrical properties were achieved.On this basis,an anisotropic and infrared light-responsive photodetector based on the 1T' Mo_xRe_1-xS₂ alloy was constructed.The research content is as follows:?1?In this work,CVD growth method is used to prepare 2D Mo_xRe_1-xS₂ alloys.In the process of exploring the growth conditions,we found that increasing the growth temperature could effectively suppress phase separation and lattice reconstruction from a thermodynamic perspective.Then,Phase-tunable Mo_xRe_1-xS₂ alloys with high quality were achieve successfully.?2?It was confirmed by polarized optical imaging,polarized Raman spectroscopy,and scanning transmission electron microscopy that the obtained Mo_xRe_1-xS₂ alloys have a uniform composition,phase structure,and crystal orientation.X-ray photoelectron spectroscopy showed that the electronic structure of the Mo_xRe_1-xS₂ alloys changed with diffrent compositions of alloys.First-principles calculations show that the concentration of dopants will affect the band structure of the alloys and achieve an effective regulation of the their bandgap.?3?Based on the obtained Mo_xRe_1-xS₂ alloys,a series of field effect transistors of alloys with different components were fabricated successfully by electron beam lithography technology.The results of the output curve showed that the contact between electrodes and the samples is closer to ohmic contact compared to MoS₂ and ReS₂ devices.Furthermore,these alloys reveal tunable conduction behavior from n-type to bipolar and p-type in 1T' phase,as well as novel "bipolar-like" electron conduction behavior in 2H alloys.Combining the measurement of electrical transmission properties with the results of calculations,we found that the Mo_xRe_1-xS₂ alloys exhibit a strong bandgap bowing effect in two distinct phase structures.Therefore,the alloy samples produced a photoresponse based on the photoconductive mechanism for different lasers.In addition,the photocurrent in the devices of 1T' phase alloys also showed a significant dependence on the angle of polarized light.The unique properties not found in single-phase alloys provide the feasibility of potential applications for new photonic and optoelectronic devices.