Maximum stable zone length in float-zone growth of small-diameter sapphire and silicon crystals

Maximum stable lengths of the floating-liquids zone (lmax) were measured in the small-diameter (d=0.25–1.5 mm) float-zone crystal growth of sapphire and silicon. A 100-W cw CO2 laser was used as power source. The measured ratios of lmax/d for sapphire and silicon are in good agreement with the theoretical analyses by Coriell, Hardy, and Cordes in the limiting case of small crystal diameters and by Rayleigh, assuming zero gravity.