Numerical Simulation Of The Transport Characteristics In The LEC Melt And Study Of The Crystal Growth Mechanism By The Gel Method

The intersections and syntheses between different disciplines and the penetrating into the microcosm are the two important characteristics of the science research at present. The cross between thermal science and material science has become the vigorous growth point of the new subject in the recent years. At the same time, the coming forth of some neoteric measuring instruments such as the Atom Force Microscope make it possible for people to explore the unknown microcosm. With the aid of basic theory of the thermal science, the numerical simulation is performed to study the characteristics of heat and mass transport in the melt during crystal growth, and the Atom Force Microscope is used to observe the microtopography on the growth interface in order to study the crystal growth mechanism in the present dissertation. Gallium arsenide(GaAs) and potassium perchlorate(KClO4) are selected as research objects, respectively. The former is important compound semiconductor material and usually grown from melt, and the latter shows excellent electronic and optical properties and is suitable for gel crystal growth. The main contents are:(1) A three-dimensional and time-dependent turbulent mathematical model is established for the heat,momentum and mass transport in the Liquid Encapsulated Czochralski (LEC) GaAs melt, in which the dopant segregation effect at the melt/crystal interface is considered. The numerical method is based on a finite volume discretization on staggered grids. A low-Reynolds number k-εturbulent model is proved to be suitable for capturing accurately the essentials of flow driven by temperature gradient and rotation in the melt. The turbulent mathematical model is used to simulate the CZ silicon melt convection in the previously published experiment, and its validity is evaluated by comparing the results with the experimental data.(2) For the natural convection driven by the buoyancy and Marangoni force in the melt, the effects of the change of the buoyancy and Marangoni force on the flow state are analyzed by changing the temperature difference between the crystal and the crucible walls. The results show that the flow will transform from axisymmetric steady flow to non-axisymmetric oscillatory flow when the temperature difference exceeds the critical value, and that the mechanism of the transform is attributed to the Marangoni instability, and that the critical temperature difference value is found to be almost independent of the melt depth in the crucible. The thermal wave patterns are found to...