Enhancement of ionic conductivity in novel LiON-AlOx multilayer heterostructures prepared by atomic layer deposition

Abstract A novel heterostructured multilayer thin-film solid electrolyte consisting of LiON-AlOx was synthesized by atomic layer deposition (ALD). The ALD-derived films were grown about 200 °C on SiO2/Si substrate by an alternating deposition of lithium oxynitride (LiON) and AlOx sublayers with 1–6 nm thickness and then characterized by various methods for roughness, homogeneity, crystallinity, thickness, composition, chemical environment, and ionic conductivity. The desired layer-by-layer structure of the films was confirmed by both high-resolution transmission electron microscopy and time-of-flight secondary ion mass spectrometry. Compared to pure LiON films without insulating AlOx interlayers, the ionic conductivities of multilayer LiON-AlOx films with various nanoscale sublayers are enhanced due to channeling effects between the heterointerfaces of nanoscale sublayers, while the activation energies are increased due to the incorporation of non-conducting AlOx sublayers. Thickness-dependent conductivity of the multilayer LiON-AlOx films indicates that 3.2 nm of LiON sublayer alternatively combined with 1 nm AlOx sublayer has the best conduction performance. The film with 15 bilayers exhibits a conductivity of 6.2 × 10−4 S/cm at 160 °C with an activation energy of 0.57 eV.