Reliable high work-function molybdenum dioxide synthesis via template-effect-utilizing atomic layer deposition for next-generation electrode applications

Abstract

MoO₂, a conductive metal oxide, has attracted considerable attention as an electrode material in metal–insulator–metal (MIM) capacitors owing to its crystallinity and high work function. However, because MoO₂ is a metastable phase, it is difficult to deposit it using a chemical reaction-based thin film deposition method, which limits its practical device application. In this work, we developed an atomic layer deposition (ALD) process for MoO₂ thin films exhibiting high crystallinity and a very high work function of 5.5 eV. A mechanism in which the metastable MoO₂ phase is stabilized and crystallized was revealed based on the “template effect” by the interfacial layer formed on a substrate surface during the deposition process. Furthermore, the template effect governed not only the crystallinity but also the stoichiometry of the deposited thin film. By employing MoO₂, a rutile TiO₂ thin film exhibiting a dielectric constant as high as 150 was obtained, which is the highest value ever reported. The high work function was also attributed to leakage current suppression in the MIM capacitor. Therefore, the proposed MoO₂ ALD is applicable to developing next-generation dynamic-random-access-memory devices.