Epitaxial Film Growth of LiBH₄ via Molecular Unit Evaporation

Complex hydrides have attracted considerable attention in fields including fast ion conduction and hydrogen storage. To understand the physical properties and to expand the fields of application of complex hydrides, physically well-defined epitaxial films that can facilitate the investigation of intrinsic properties and interfacial effects need to be fabricated. However, epitaxial films of complex hydrides remain difficult to produce. This study reports the growth of single-phase epitaxial films of the complex hydride LiBH4 and their high Li-ion conductivity of 1 × 10–2 S cm–1 at 423 K. To achieve this, we used a low-power infrared laser to induce the evaporation of LiBH4 molecular units; with this technique, we were able to deposit [BH4]− complex anions while preserving their molecular integrity, producing epitaxial films with high crystallinity, flat surface, and high Li-ion conductivity. These achievements will establish a solid basis for epitaxial growth of complex hydrides and pave the way for advanced studies of complex hydrides including surface and interfacial phenomena.