The integration of ultrathin dielectrics on two-dimensional (2D) semiconductors is essential for advancing beyond-Si electronics. However, the intrinsic inertness of van der Waals 2D basal planes remains a primary bottleneck to achieving uniform dielectric nucleation and growth. Here, we introduce a small molecule inhibitor (SMI)-modulated thermal atomic layer deposition (ALD) strategy, exemplified by aluminum oxide (Al2O3) ALD on monolayer molybdenum disulfide (1L MoS2) with acetic acid (HAc) SMI. The ABC-type sequence comprises HAc inhibitor (A), trimethylaluminum (TMA) precursor (B), and deionized H2O coreactant (C). In situ quartz crystal microbalance (QCM) studies reveal robust HAc adsorption on Al2O3 and suppression of subsequent oxide growth on HAc-passivated surfaces. When applied to 1L MoS2, this inhibitory pathway enables HAc to selectively passivate nascent Al2O3 nuclei formed on the MoS2 surface, limiting their three-dimensional (3D) island coarsening and redirecting precursor adsorption toward the uncovered basal plane. Consequently, nearly continuous ultrathin (∼1.5 nm) Al2O3 films are achieved on 1L MoS2 with markedly improved uniformity compared to standard Al2O3 ALD using TMA and H2O, as validated by atomic force microscopy (AFM), cross-sectional scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectroscopy (EDS). Density functional theory (DFT) calculations further provide atomistic insight into HAc-modulated Al2O3 nucleation, corroborating the energetic preference of HAc for Al2O3 over MoS2 and attenuated TMA adsorption on HAc-passivated surfaces. Spatially resolved Raman spectroscopy also confirms that the HAc-modulated process preserves the structural integrity of 1L MoS2, with only minimal strain and doping perturbations observed after dielectric deposition. This SMI-modulated approach offers a broadly applicable framework for controlling ALD nucleation across various inhibitors, ALD chemistries, and 2D materials, opening opportunities for reliable dielectric integration in next-generation nanoelectronics.
Oh et al. (Thu,) studied this question.