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2H-SiC nano line theory calculation and solvothermal preparation

Author: LiXiaoNi
Tutor: ZhaoWu
School: Northwestern University
Course: IC Engineering
Keywords: 2H-SiC First-Principles solvothermal method
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Type: Master's thesis
Year: 2013
Downloads: 6
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Abstract


Silicon carbide (SiC) has a wide band gap, high electron mobility, high breakdown field strength and other characteristics, so that it has broad application prospects in high-temperature, high-frequency, high-power devices and optoelectronic devices. Current main research of SiC focused on synthesis and properties analysis of two categories structure which are cubic. zinc blende structure and hexagonal wurtzite structure.The main work of this paper has two aspects, the theoretical calculations and laboratory synthesis for the hexagonal wurtzite structure of2H-SiC crystal Materialss preliminary study.Ⅰ. Using the First-Principles, calculation which based on the Density Functional Theory of Theoretical calculation,2H-SiC body Materialss,2H-SiC nanowires and doped2H-SiC nanowires systems are built and calculated by using CASTEP software package in Materials Studio5.0.1、Suiting for2H-SiC Materialss calculation parameters are optimized by the2H-SiC body Materialss convergence testing, such as the Pseudopotential method for Ultrasoft pseudopotential, Correlation function for Perdew Wang (1991), K point for7×7×4, Plane wave cutoff for360electron volt, etc., These parameters have laid the foundation of2H-SiC nanowire Materialss research.2、By different diameter intrinsic2H-SiC nanowires calculating, the results show that in a certain range, the intrinsic2H-SiC nanowire systems occurre blue shift, a slight increase in the dielectric constant and the light absorption characteristics by an increase in diameter of the nanowires.3、By doped (doping elements are B, N, Al and P)2H-SiC nanowires calculating, the results show that B, N, Al elements incorporation improves the conductivity of the system, and P element incorporation has little contribute conductivity of the system. After four different doping elements alone incorporation, The band gap are reduced, absorption spectrum of systems occurre red shift, and the static dielectric constant of system has increased, which contributed greatly to Al.Ⅱ. Experiment which using Si as the silicon source. C2H5OH as carbon source, Mg as the catalyst, and polyvinyl pyrrolidone (PVP) as a co-catalyst synthesis of2H-SiC nanowire crystalline Materialss in low temperature by solvothermal method. Synthesized samples are studied by X-ray powder diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), Scanning electron microscopy (SEM).The results show that2H-SiC crystal is generated easily by the introduction of PVP, and preferably at the growth at360℃; C element and Si element are major elements of the sample which in flake morphology and less linear structure. Optimization process:Si is0.8g, C2H5OH is15ml, Mg is2;5g, PVP is0.5g, the temperature is360℃, and the time of reaction is15.5. hours.

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