COMPUTER-CONTROLLED FLOAT-ZONE CRYSTAL-GROWTH

A PC-based computer control system to automate a high-temperature floa t zone growth of titanium carbide is reported. The control strategy of the computer control system relies on the relations derived from a co mbination of empirical relations and results from detailed mathematica l analysis of the physical transports of the entire float zone assembl y. A system control computer program was written to establish real-tim e determination of the size of the molten zone from a thermal image, c ontrol parameters from established relationships, and collected proces sed data to achieve control objectives. We found that the developed co mputer control allows the growth process to be operated nearer the sta bility limit. Any slight variations in growth conditions can be correc ted in time to avoid any instability growth, which otherwise cannot be adjusted via manual control.