Chemical Vapor Deposition Two-dimensional Atomic Crystal And High-performance Electronics

During the past six decades,microelectronic devices have kept developing followed by Moore’s law,and now facing challenges including high power consumption and scaling down problem.Two-dimensional（2D）layered atomic crystal semiconductor materials with atomic thin body property and high mobility,are considered to be one of the post-Moore era logic chip materials candidates.Molybdenum disulfide（Mo S₂）has a band gap of 1-1.9e V with favorable air stability,indicating a great potential in low-power logic circuit.In recent years,scientific research reports about Mo S₂were emerging continuously,however,most of them focus on exfoliated flakes with small size and low yield,how to synthesis large-area 2D layered film remains a great challenge.Chemical vapor deposition（CVD）provide the possibility of growing high quality and large-area film,while growing highly crystallization and layer-controlled large single-crystal films were fewly reported.Besides,high-performance Mo S₂transistors based on CVD were facing a great challenge as well.In this thesis,toward two-dimensional atomic crystal molybdenum disulfide,controllable growth of high mobility and layer-controlled Mo S₂film with large single-crystal was explored.Conprehensive material characterizations,high-performance Mo S₂transistors and low frequency electrical noise were also discussed.The research foucus on the following several aspects:Firstly,controllable atmospheric pressure chemical vapor deposition（APCVD）growth of monolayer Mo S₂films has been explored.Around mass-transport and surface-reaction limit,monolayer Mo S₂large single-crystal size more than half of millmeter is acquired on molten glass,with electron mobility of 24 cm²/V?s at room temperature,and 84 cm²/V?s at20 K.APCVD growth of high mobility monolayer Mo S₂single-crystal size up to record high value,laid the foundation for subsequent work.Secondly,highly crystallization bilayer Mo S₂large single-crystal films and material characterizations have been systematically discussed.Large-area bilayer Mo S₂single-crystal films begin to appear on molten glass at high Mo precursor mass flux.Bilayer Mo S₂domain size greatly depend on Mo precursor weight,and reach record high200μm.A mass-driven reaction kinetics model of bilayer Mo S₂was put forward,while mass-transport region was dominant on growth rate.The spectral characteristics,single-crystal property and stack mode of bilayer Mo S₂were discussed.Highly crystallization and controllable growth of bilayer Mo S₂large single-crystals provide a prerequisite for the preparation of high-performance Mo S₂transistors.Thirdly,high-performance Mo S₂transistors and low frequency noise were systematically researched.Compared with single-layer Mo S₂,bilayer Mo S₂has higher density of states（DOS）and electron mobility,and preserves 2D materials atomic thin body nature at the same time.Bilayer Mo S₂transistors show 10⁶on-off ratio,which greatly restrain the short channel effect（SCE）.On-current reach 438μA/μm at room temperature,and reach record high 1.524 m A/μm at 4.3 K.Bilayer Mo S₂mobility up to 36 cm²/V?s at room temperature,and reach record high 127 cm²/V?s at 4.3 K.The current noise power spectral density of Mo S₂transistor follow the change law of 1/f at low frequency,with noise amplitude up to 3.2×10^-8.The low frequency noise of Mo S₂transistor in sub-threshold region and weak inversion region derive from carrier number fluctuation,while in strong inversion region derive from mobility fluctuation.The noise figure of merit Hooge parameter up to 3.25×10^-3.The noise level of Mo S₂transistor reach 10^-9μm²/Hz order at 10 Hz,reduce contact resistance and improve mobility are crucial for optimizing noise level.These results improve our understanding and cognition of molybdenum disulfide synthesis and device performance,illuminting the way of molybdenum disulfide research and application in the future.