Functionalization-Free Atomic Layer Deposition of Sub-1 nm EOT HfO2 Directly on MoS2 for Gate-All-Around Field-Effect Transistors

Layered semiconductors offer a promising route beyond conventional silicon technology but face challenges in integrating high-k dielectrics due to their dangling-bond-free surfaces. Here, we report a direct atomic layer deposition approach, termed HALO (High-dose precursor immersion, Adsorption enhancement, and Low-temperature Oxide improvement) ALD, enabling uniform HfO2 growth on two-dimensional (2D) materials without surface functionalization. The HALO process improves nucleation and interface quality, yielding smooth high-k films (∼0.1 nm roughness). MoS2 dual-gate field-effect transistors (FETs) exhibit an equivalent oxide thickness of 0.83 nm, a subthreshold swing of 80 mV dec–1, and breakdown fields up to 9 MV cm–1. Reliability studies, including bias stress and thermal tests, confirm stable device operation. This approach further enables conformal high-k integration in gate-all-around structures, providing a scalable pathway for three-dimensional (3D) integration of 2D electronics.