Eliminating Nucleation Delay for Atomic Layer-Deposited Low-Defect Dense Multi-Component Thin Films through Preoccupation of Interstitial Sites

Atomic layer deposition (ALD) is advantageous in the flexible and precise control of the composition and thickness of thin films. However, the nucleation delay during the deposition of multicomponent films leads to unexpected thickness and composition, the mechanism of which is still ambiguous. Herein, we reveal that the surface formed by a certain precursor is self-limiting for itself; there remain interstitial sites for other precursors. This phenomenon results from differences in the steric hindrance and molecular volume between different precursors. To address this issue, we develop a complementary supercycle process consisting of several three-step ALD subcycles that eliminates nucleation delays by preoccupying interstitial sites through a novel three-step subcycle design. Unlike conventional supercycle processes, our approach intentionally aligns the second precursor of one subcycle with the first precursor of the next, thereby preoccupying interstitial sites and suppressing the nucleation delay. Applied to Indium-Tin-Zinc-Oxide (ITZO) thin films, this method produces denser films with fewer defects compared to the conventional supercycle process. The resulting enhancement-type ITZO thin-film transistors (TFTs) achieve superior electrical properties (mobility(μ): 27.31 cm² V^-1 s^-1, drift of threshold voltage (Δ<i>V</i>_th): +0.8 V/-0.4 V (@ ± 1 MV cm^-1, 3600 s)). Beyond ITZO, this work establishes a universal framework for defect-suppressed growth of single-/multicomponent oxides via ALD, directly addressing a critical bottleneck in high-performance electronics manufacturing.