Fluid Flow and Front Shape of the Vertical Bridgman Crystal

• Main Authors: Cheng-Chung Ting, 丁建中
• Other Authors: Chung-Wen Lan
• Format: Others
• Language: zh-TW
• Published: 1994
• Online Access: http://ndltd.ncl.edu.tw/handle/14446289013472787163

碩士 === 國立中央大學 === 化學工程研究所 === 82 === The control of the growth front(melt/crystal interface) in the vertical Bridgman(VB)crystal growth is necessary to growth a crystal with desirable quality for device applic- ations. Usually, a flat or slightly convex interface shape toward the melt during crystal growth is most desirable for growing single crystals with low defects. However, in prac- tice it is very difficult to manipulate the melt and crystal temperature distributions that lead to the desirable inter- face. Owing to the complexity and invisibility of the system the control of the growth front shape could be rather diffi- cult.As it is, an effective interface control relies on a thorough understanding of the interactions of solidification phenomena and ambient thermal environments. Therefore, to study the VB crystal growth systematically, direct observation of crystal growth in a computer-controlled transparent multi- zone furnace and the heat flow simulation are conducted. In the crystal growth experiments, sodium nitrate is chosen as a model material. Owing to the transparent melt and crystal, the growth front during crystal growth in the transparent furnace with a specified heating profile can be visualized.