Growth kinetics of solid-liquid Ga interfaces: Part I. Experimental

A technique based on the Seebeck effect was used to determine directly the solid-liquid (S/L) interface supercooling and toin situ monitor the interfacial conditions during growth of high-purity Ga single crystals from a supercooled melt. Using this nonintrusive technique, the growth kinetics of faceted (111) and (001) interfaces were studied as a function of the interface supercooling in the range of 0.2 to 4.6 K, corresponding to bulk supercoolings of about 0.2 to 53 K. In addition, the growth kinetics have been determined as a function of crystal perfection related to the emergence of dislocations at the S/L interface. The results show that at low super-coolings, the faceted interfaces grow with either of the lateral growth mechanisms: two-dimensional nucleation-assisted (2DNG) or screw dislocation-assisted (SDG), depending on the perfection of the interface. At increased interfacial supercoolings, however, both growth rates (2DNG and SDG) become a linear function of the supercooling. Application of the existing growth theories to the experimental results gives only qualitative agreement and fails to predict the observed deviation in the kinetics at high supercoolings. A theoretical treatment of the growth of faceted interfaces will be given in Part II of this series.¹ Formerly Research Assistant with the Department of Materials Science and Engineering, University of Florida. This paper is based on a presentation made in the symposium “The Role of Ledges in Phase Transformations” presented as part of the 1989 Fall Meeting of TMS-MSD, October 1–5, 1989, in Indianapolis, IN, under the auspices of the Phase Transformations Committee of the Materials Science Division, ASM INTERNATIONAL.