Overcoming the Critical Thickness Limit: Interfacial Control of Crystallization Pathways in Atomic-Scale Dielectric Thin Films.

Abstract

Fundamentally, maintaining crystalline quality at the few-nanometer scale is challenging due to reduced diffusion pathways and high surface energy. In many advanced technologies, particularly in modern electronics, achieving highly crystalline thin films is crucial for maintaining the material's intrinsic properties and ensuring stable, high-performance operation. In this work, we investigate how in-plane and out-of-plane diffusion processes govern the structural evolution of films grown by conventional atomic layer deposition (ALD) and atomic layer modulation (ALM). As an extension of ALD, the ALM process allows more precise control over the compositional uniformity in both lateral and vertical directions at the atomic scale. Using the ALM process, we fabricated highly crystalline sub-2 nm Y-doped ZrO₂ (YZO) thin films that exhibit significantly improved electrical properties. This study demonstrates that a more uniform distribution of Y dopant promotes atomic diffusion, which in turn stabilizes a well-crystallized cubic (111) phase. At a thickness of 2 nm, the YZO ALM films exhibit a leakage current density nearly 300 times lower than that of YZO ALD films. This study highlights the critical role of in-plane and out-of-plane diffusion in achieving ultrathin, highly crystalline films for next-generation electronic devices.