A generalized ionic approach to the epitaxial growth of yttrium iron garnet films in molten solutions

An ionic approach to the liquid-phase-epitaxy (LPE) growth of yttrium iron garnet (YIG) films suitable for microwave signal processing and other integrated electronic or magnetic applications has been developed. By straightforwardly extending Giess' theory and by accounting for the conspicous amount of previous published data, the proposed model figures out a unified description of the solubility characteristics of the YIG system. From the inferred values of the main thermodynamic quantities (the enthalpy of solution of 72 kcal mol-1 and the entropy of formation of 26 10-3 kcal mol-1 K-1), the kinetic properties of the films during a growth run have been analyzed. Particular emphasis has been given to the LPE growth of very thick films (> 100 um) by means of small melts (i.e., with a weight less than 0.5 kilograms). To test the validity of the model, the calculated thickness values have been compared to experimental thicknesses as measured on a series of YIG films purposely grown in three PbO-B2O3 fluxed melts. In the comparison, an agreement better than 95% has been observed. © 1987.