Two-dimensional (2D) transition metal dichalcogenides (TMDCs) hold great promise for next-generation nanoelectronics, but integrating high-quality, ultrathin gate insulators remains challenging. Although atomic layer deposition (ALD) is the industry standard for depositing conformal dielectrics with angstrom-level precision, its effectiveness on 2D materials is limited due to their dangling-bond-free surfaces, which restrict nucleation to defects and grain boundaries.

Our research focuses on addressing these fundamental challenges to enable reliable dielectric integration on 2D semiconductors. In particular, we need to understand how ALD precursor chemistry affects nucleation and device performance, and how substrate properties impact ALD film growth. We explore physisorption-assisted ALD (PA-ALD) as an industry-compatible approach to achieve uniform dielectric growth. We are also extending this approach to high-k dielectrics with hafnium and zirconium precursors on CVD-grown MoS₂ and investigating how substrate properties impact ALD nucleation on both exfoliated and CVD MoS₂.

Above: Representative SEM images after 30 cycles of AlO_x ALD deposited on monolayer MoS₂ using TMA and TIBA as the precursor. The white/light gray regions arise from the AlO_x and the darker regions derive from the monolayer MoS₂. The thickness reported on each image represents the thickness measured on SiO₂ by spectroscopic ellipsometry (SE). The percentage shown on each SEM image represents the real coverage of AlO_x on MoS₂.

A.B. Shearer et al., ACS Nano (2025); https://doi.org/10.1021/acsnano.5c10705