Interface‐Directed Two‐Dimensional Growth of Non‐Layered NiO on MoS 2 Under Coupled External Fields

The controlled growth of two‐dimensional (2D) non‐layered transition metal oxides remains a key challenge in low‐dimensional material synthesis. Achieving atomically precise construction of 2D structures requires a fundamental understanding of how external fields and interfacial interactions govern nucleation and growth processes. In this work, amorphous NiO x (a‐NiO x ) was deposited onto monolayer MoS 2 , and its transformation into crystalline 2D NiO nanosheets was directly visualized in situ using environmental transmission electron microscopy. The electron beam induces the decomposition of a‐NiO x into mobile NiO x species, which migrate and nucleate on MoS 2 , demonstrating the synergistic roles of the electron beam and thermal field in NiO cluster formation and interface‐dominated epitaxial growth. Combined notch‐filtered imaging and theoretical calculations reveal that Ni–O units preferentially attach at the NiO/MoS 2 interface to form one‐dimensional growth fronts, while oriented attachment proceeds via nanosheet rotation, interfacial fusion, and defect‐mediated reconstruction, culminating in lattice relaxation into a single‐crystalline structure. High‐throughput selected‐area electron diffraction further uncovers the modulation of external fields on the multi‐path structural evolution of NiO x . This work establishes an in situ strategy to resolve nucleation and growth pathways of 2D heterostructures, enabling active control over the 2D growth of non‐layered metal oxides and advancing deterministic atomic‐level construction.