Synthesis and Crystallization of Atomic Layer Deposition β-Eucryptite LiAlSiO₄ Thin-Film Solid Electrolytes

Atomic layer deposition (ALD) was used to control the stoichiometry of thin lithium aluminosilicate films, thereby enabling crystallization into the ion-conducting β-eucryptite LiAlSiO₄ phase. The rapid thermal annealed ALD film developed a well-defined epitaxial relationship to the silicon substrate: β-LiAlSiO₄ (12̅10)||Si (100) and β-LiAlSiO₄ (101̅0)||Si (001). The extrapolated room temperature ionic conductivity was found to be 1.2 × 10^-7 S/cm in the [12̅10] direction. Because of the unique 1-D channel along the c axis of β-LiAlSiO₄, the epitaxial thin film has the potential to facilitate ionic transport if oriented with the c axis normal to the electrode surface, making it a promising electrolyte material for three-dimensional lithium-ion microbatteries.