Vibration controlled convection - Preparation and perspective of the Maxus4 experiment

A comparatively new possibility to influence convection in crystal growth m elts is the application of controlled interface vibration, especially in sy stems with free melt surfaces like the float-zone process. The present pape r concerns the development and testing of a vibrational device which will b e integrated into a microgravity crystal growth facility for the growth of silicon crystals. III the case of silicon grown by the float-zone technique , time-dependent thermocapillary convection is present even under micrograv ity and leads to unfavourable variations of the crystal composition profile . The developed setup can operate in the range of approximately 0.1 to 50kHz producing maximum amplitudes of 0.25 mum (non resonance case) and 3.5 mum ( resonance case) respectively. The power consumption is below 5W, the maximu m operation temperature of the device is restricted to 200 degreesC, limite d by an epoxy-based connection between vibrator and sample. The first micro gravity application will be during the European Maxus 4 campaign in April 2 001. (C) 2001 Elsevier Science Ltd. All rights reserved.