This work established the fundamental growth principles needed to produce high-quality epitaxial CrB₂/TiB₂ diboride superlattices for neutron-optical applications. Through a systematic exploration of sputtering strategies—using compound targets, co-sputtering, ion-assisted growth, and lattice-matched substrates—the project demonstrated how layer composition, deposition conditions, and substrate choice govern structural quality, interface sharpness, and growth mode.
A wide range of complementary techniques, including X-ray diffraction, neutron reflectivity, ToF-ERDA, STEM, and nanoindentation, were employed to map the structural and chemical evolution of the superlattices. The studies showed that a layer-thickness ratio around 0.3 consistently yielded the highest structural quality, and that stoichiometry control in TiBy layers was crucial to avoid B-rich boundary formation. The introduction of ion-assisted epitaxy and the use of a lattice-matched 4H-SiC substrate further enabled single-crystal-quality superlattices with exceptionally sharp interfaces.
Altogether, the project paved the way for using diboride superlattices as highly efficient neutron-interference optics and provided new insights into the growth and interface physics of transition-metal diborides.