Induced striations in LPE garnet layers

Abstract

At a given chemical eomposition of a solution the composition of the deposited material depends on the growth rato. Therefore well defined changes of the growth tate can be used to prepare single crystals of LPE layers with defined changes of the composition. In the case of garnet single crystals the growth rato has been modulated by the variation of the undercooling to generate induccd striations, which aro a tool in investigating and optimizing the growth process in high tempcrature solutions. During the course of liquid phase epitaxy expcriments (LPE) of garncts the variations of the growth rato were produced by changing the rotation rato to generate a layered structure. By measuring the thickness of the layers optically one gets the dependences of the growth rateas a function of the time, rotation rate, and undercoo]ing by one experiment with one substrate in each case.Based on the work of LEVINSTEIN et al [1] and GIESS ot al [2] the isothermal LPE dipping method with axial substrate rotation plays the dominant tole in growing epitaxial garnet films on nonmagnetic substrates for applications in. the microwave and memory technique. Besides this technical importance, the same teehnology is excellently suitable for studying both the elementary processes in the course of crystal growth and the relation between crystal growth, the real structure, and properties.In this paper the possibility will be shown of measuring of the growth rato economically and exactly on the basis of induced striations in opilayers, the growth rato being one of the most important parameters of aH problems linked with crystal growth.Using the diffusion boundary layer approximation the steady state growth rato v in the solvont-solute binary system is given for diluted solutions byCS ~eff (~eff ropresents the integral resistivity D •eff ~ 1 + --(2) D D kwhich eontains the transport (~/D) sueh as eonveetion, diffusion and interfaeial proeesses (l/k) such as desolvation, adsorption, surface diffusion, incorporation. The moaning of symbols is explained in the list at the end of the text. The so-called diffusion boundary layer thicknes ~ (see Fig. 1) is proportional to the negative square root of the rotation rate (~ ~--r -1/2) aceording