Experimental investigations on thermal, thermocapillary and forced convection in Czochralski crystal growth configuration

摘要

One of the greatest technological and scientific challenges of crystal growth is to achieve homogeneity of the material properties (e.g. electrical resistance in the micro range). According to the present know-how, the cause of fluctuations of the electrical resistance is due to fluctuations of the growth rate of the crystal. One of the possible causes for fluctuations of the growth rate is the instationary convection in the melt. The focus of the project is to examine the influence of the thermal Marangoni effect on the temperature and velocity field due to spatial and temporal variations of the temperature field adjusted from the outside. Moreover, the aims of the project are to analyse the stabilisation effect of rotation on thermocapillary flow, to determine the start of oscillatory motions and to examine the transition of an oscillatory mode to higher modes as well as the transition to turbulent motion.