GB967844A - A process for treating material which crystallises - Google Patents

Abstract

967,844. Zone-melting. SIEMENS-SCHUCKERTWERKE A.G. April 6, 1962 [April 11, 1961], No. 13463/62. Heading B1S. [Also in Division H5] In the formation of a single crystal rod by zone-melting or crystal-pulling, the crosssection of the melt being crystallized is deformed to correspond to the natural crosssectional shape of the crystal. In the case of silicon or germanium, the cross-section is an equilateral triangle when the axis of symmetry is the (111)-axis, a square when the axis of symmetry is the (100)-axis, and a rhomb when the axis of symmetry is the (110)-axis. In the case of zinc or cadmium, the cross-section is a hexagon when the axis of symmetry is the (0001)-axis. In the case of potassium chloride or tungsten, the cross-section is a triangle or rectangle. Deformation may be by the use of heated argon or helium (Fig. 1), an electrostatic field (Fig. 3), or an electromagnetic field (Fig. 4). The electrostatic field may be formed by the application of a potential difference of 10 kV. in a vacuum or protective gas atmosphere. The electromagnetic field may be formed by feeding a current of 10 kc./s. into an induction coil fed with a heating current of 4 mc/s., the coil having the shape shown in Figs. 5 or 6. The coil may be of silver-plated copper tubing internally cooled by liquid or gas. Different methods of deformation may be combined. Deformation may be effected in the last passage only of a molten zone. Specifications 888,148 and 889,160 are referred to.