Preparation And Properties Of Molybdenum Disulfide Thin Films

Molybdenum disulfide（MoS₂）has become the most promising material among transition metal sulfides（TMDs）in recent years due to its excellent optical properties,tunable band gap structure and unique conductive properties.At the same time,thin-film materials have become an effective means to explore semiconductor properties,obtain special structures,and prepare functional devices by virtue of their thickness.Therefore,it is urgent to investigate the properties of MoS₂thin films and their applications in the field of photoelectric conversion.In this thesis,the relevant properties of molybdenum disulfide were investigated through physical modeling,numerical simulation and structure optimization on the one hand,and the microscopic growth process of molybdenum disulfide thin film was simulated by Monte Carlo method,and the spectral response characteristics of the detector based on molybdenum disulfide thin film with MSM structure were simulated by Silvaco software on the other hand.The effects of sputtering time,sputtering power,deposition temperature and annealing temperature on the quality of film formation were studied in order to lay the foundation for the preparation of high-quality molybdenum disulfide-based thin film material detectors.The main work was as follows.Firstly,the optical,structural and electrical properties of molybdenum disulfide were simulated and calculated by modeling 2H-MoS₂crystal model through software simulation based on density generalized first principles.The Monte Carlo method was also used to simulate and calculate the microscopic deposition process of the films and summarize the effects of different independent variables（deposition temperature,number of particles,maximum migration steps）on the microscopic growth of the films to provide a reference for the characterization of the MoS₂surface morphology prepared in the subsequent experimental part.Secondly,MoS₂ thin films were deposited on quartz glass and single crystal silicon using a combination of magnetron sputtering method and annealing process.The structural,optical,and electrical properties of the films were characterized and analyzed by modern inspection means,while the band gap of the films was calculated by combining the Tauc equation to investigate the effects of four process variables（sputtering time,sputtering power,deposition temperature,and annealing temperature）on the film formation.The characterization results demonstrate that the increase of sputtering power and sputtering time significantly affects the layer thickness,morphology,absorption and transmission properties of the films;the increase of substrate temperature after 300°C accelerates the Mo-O bonding in the films,which leads to the formation of Mo O₃impurities and affects the absorption and transmission variation pattern of the films;the annealing temperature significantly affects the crystallization degree of the films,and the films have the best conductivity when the annealing temperature is 500°C The film has the best electrical conductivity when the annealing temperature is 500°C.Finally,based on the absorption-transmission results obtained from the simulations,a metal-semiconductor-metal structure molybdenum disulfide-based detector model is established by combining the mobility model and the drift-diffusion model,and the influence of various structural parameters on the operating performance of the device is calculated and analyzed.The study shows that the increase of the active region thickness will enhance the peak intensity and red-shift the peak position of the detector;the width of the electrode has no significant effect on the operating parameters of the device,but the spacing of the electrode is negatively correlated with the operating current of the device.