Flux residule on liquid phase epitaxial Bi-substituted garnet films and wetting between wafers and flux

Abstract

Flux residue on the surface after liquid phase epitaxial (LPE) growth of garnet films, which is a serious problem particularly for Bi-substituted garnet films, was studied from the viewpoint of wetting between garnet surface and fluxes. Two kinds of experiments were carried out: (i) observation of the flux residue mode on the surface of (LuBi)3Fe5O12 garnet films with various crystallographic orientations and (ii) contact angle measurements for various combinations of garnet wafers and flux compositions. Flux residue took place on the surface of {100} and {111} (LuBi)3Fe5O12 garnet films, where the contact angle was 0°: spreading-type wetting. On the {100} wafers spreading took place regardless of wafer and flux compositions. The order of contact angles inferred from data observed for various combinations of wafers and fluxes is as follows: θ211⋍ θ110 > θ111θ100 = 0°. The order agrees with that of morphological importance determined by Bennema et al. except for the {100}. LPE garnet films are more wettable than GGG substrates, regardless of water orientation.