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Adsorption and surface diffusion of silicon growth species in silicon carbide chemical vapour deposition processes studied by quantum-chemical computations

机译:量子化学计算研究碳化硅化学气相沉积过程中硅生长物质的吸附和表面扩散

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The effect chlorine addition to the gas mixture has on the surface chemistry in the chemical vapour deposition (CVD) process for silicon carbide (SiC) epitaxial layers is studied by quantum-chemical calculations of the adsorption and diffusion of SiH2 and SiCl2 on the (000-1) 4H-SiC surface. SiH2 was found to bind more strongly to the surface than SiCl2 by approximately 100 kJ mol~(-1) and to have a 50 kJ mol~(-1) lower energy barrier for diffusion on the fully hydrogen-terminated surface. On a bare SiC surface, without hydrogen termination, the SiCl2 molecule has a somewhat lower energy barrier for diffusion. SiCl2 is found to require a higher activation energy for desorption once chemisorbed, compared to the SiH2 molecule. Gibbs free energy calculations also indicate that the SiC surface may not be fully hydrogen terminated at CVD conditions since missing neighbouring pair of surface hydrogens is found to be a likely type of defect on a hydrogen-terminated SiC surface.
机译:通过量子化学计算研究SiH2和SiCl2在(000)上的吸附和扩散,研究了向混合气中添加氯对碳化硅(SiC)外延层化学气相沉积(CVD)过程中表面化学的影响。 -1)4H-SiC表面。发现SiH2与SiCl2的结合力比SiCl2强得多,约为100 kJ mol〜(-1),并且能垒低50 kJ mol〜(-1),以扩散到完全氢封端的表面上。在没有氢封端的裸露SiC表面上,SiCl2分子的扩散势垒较低。与SiH2分子相比,SiCl2被化学吸附后需要更高的活化能才能解吸。吉布斯自由能计算还表明,在CVD条件下,SiC表面可能未完全氢封端,因为发现相邻的一对表面氢缺失是氢封端SiC表面上可能的缺陷类型。

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