Ion beam sputter-fabrication of Bi-YIG films for magnetic photonic applications

We report the fabrication of polycrystalline and epitaxial Bi-substituted yttrium gallium iron garnet films on amorphous oxide coated Si wafers and single crystalline gadolinium gallium garnet (GGG) substrates for potential magnetic photonic device applications via reactive ion beam sputtering of a single phase (Bi_0.8Y_2.2)(Ga₁Fe₄)O₁₂ target. The observed Bi-YIG film magnetic properties are sensitive to sputtering parameters like the reactive molecular oxygen ion or radical neutral oxygen atom flux substrate impingement, and the specular or nonspecular geometry control of the reflected neutral substrate bombardment. Nonferrimagnetic amorphous Bi-YIG films are obtained using the specular sputtering geometry that can be recrystallized as randomly oriented single-phase YIG films with in-plane anisotropy using post-deposition rapid thermal annealing (RTA). Also, nonspecularly sputtered Bi-YIG films with improved interfaces and weak nanocrystallinity can be fabricated, yielding "as grown" ferrimagnetic behavior that can be further improved by RTA. Epitaxial Bi-YIG films on GGG with extremely soft magnetic characteristics and strong in-plane anisotropy have also been fabricated.