Meniscus Shape Calculation And Stability Analysis Of CdZnTe Cryatals Detachment Growth

The detached solidificaiton is a new technique which is developed in the latest twenty to thirty years. The phenomenon of detached solidification was first noticed on Skylab in 1974. A series of experiments after solidification by the Bridgman technique in the spacecraft showes that the sample is totally free inside the crucible. Obviously, the crystal is growed without contact with the crucible. The contactless growth can produce crystals of dramatically improved quality(reduction inparasitic nucleation, fewer dislocations, less strains, etc). This phenomenon is described as"detached growth"or"dewetted growth".This technique could be applied to the growth of large diameter crystals known to be very sensitive to the contact with crucible , especiallyâ…¡-â…¥(such as CdZnTe). CdZnTe crystal is an important material which can be used in the fields of astrophysics, industry testing, nuclear radiation detecting and nuclear medicine.In this thesis a summary is presented about the origin, mechanism and the merits of this new phenomenon. It introduces the present research status and achievements of this new technique. Although there has achieved several successful experiments in space and on ground, however, up to now, the mechanisms which give rise to detachment are not completely recognised, so it is necessary to get a further reseach on this new phenomenon.Based on previous research works, firstly, the present paper established the mathematical models of detached solidification on the microgravity and normal gravity condition, and obtained the meniscus shape of CdZnTe crystals detached solidification. Secondly, the stability analysis are performed by Lyapunov method. It contains:â‘ The mathematics models of detached solidification in the microgravity and the normal gravity are established. The necessary conditions for detached solidification are given., and the influence of different factors for the meniscus shape is analysed.â‘¡A series stability analysis , which include the coupling geometry, heat transfer and the pressure difference between cold and hot ends of the crucible , are performed by Lyapunov method.The results show that the growth angle, contact angle and the pressure difference between cold and hot ends of the crucible play very important roles in the detached solidification. And the detached solidification is most likely stable in the microgravity.