  We investigate the integration of Al2O3 high-k dielectric on two-dimensional
(2D) crystals of boron nitride (BN) and molybdenum disulfide (MoS2) by atomic
layer deposition (ALD). We demonstrate the feasibility of direct ALD growth
with trimethylaluminum(TMA) and water as precursors on both 2D crystals.
Through theoretical and experimental studies, we found that the initial ALD
cycles play the critical role, during which physical adsorption dominates
precursor adsorption at the semiconductor surface. We model the initial ALD
growth stages at the 2D surface by analyzing Lennard-Jones Potentials, which
could guide future optimization of the ALD process on 2D crystals.
