Effect of Subcycle Arrangement on Direct Epitaxy in ALD of LaNiO3

Abstract

Monolithic device integration of crystalline complex oxide thin films can open for smarter and more sustainable devices in electronics and energy technology. However, the facile integration of such compounds has so far been incompatible with the present production lines for electronics. Atomic layer deposition (ALD) is already well-integrated for the production of amorphous binary oxides in electronics, but extending the technique to crystalline complex compounds has proved challenging. Herein, we show how the subcycle arrangement (i.e., the overall order of binary subcycles) plays a crucial role in the formation and quality of crystalline complex oxides by ALD, exemplified by the growth of LaNiO3. We show that an approach somewhere in between the traditional homogeneous and multilayer approaches provides the best platform for crystalline growth. Based on these results, we hypothesize that choosing multilayer unit slab thicknesses close to the interlayer distances in the target crystalline structure, while still maintaining the correct cation composition, enhances as-deposited crystallinity and in turn the functional properties. We believe this approach can be used to extend the toolbox of attainable crystalline complex oxides by ALD and establish utilization of the technique for monolithic integration of functional thin films.