Impact of Co-Reactants in Atomic Layer Deposition of High-κ Dielectrics on Monolayer Molybdenum Disulfide

High Resolution Image Download MS PowerPoint Slide The integration of single-layer transition metal dichalcogenides (TMDCs) in nanoscale field-effect transistor devices requires the deposition of a high dielectric constant (high-κ) material to act as the gate dielectric. Traditional thermal atomic layer deposition (ALD) is commonly used to deposit dielectrics on three-dimensional substrates, but ALD of high-κ materials on monolayer TMDCs is more challenging. Thermal ALD with water (H 2 O) co-reactant often results in incomplete and nonuniform dielectric growth on atomically thin TMDCs, owing to a chemically inert basal plane. The development of alternative ALD processes for the realization of dielectric layers on monolayer TMDCs is therefore important. Here, we study oxygen (O 2 ) plasma and ozone (O 3 ) as co-reactants for the ALD of aluminum oxide (Al 2 O 3 ) and hafnium dioxide (HfO 2 ) on monolayer molybdenum disulfide (1L MoS 2 ) films. By employing a robust characterization process that combines atomic force microscopy, Raman/photoluminescence spectroscopy, and X-ray photoelectron spectroscopy, we reveal growth of high-κ dielectrics by plasma-enhanced ALD with O 2 plasma oxidant damages the underlying 1L MoS 2 via oxidation to molybdenum trioxide (MoO 3 ). No significant deleterious oxidation to MoO 3 is observed following O 3 -based deposition on 1L MoS 2, and we demonstrate the growth of HfO 2 via thermal ALD with O 3 co-reactant. This work reveals the impact of ALD processes on 1L MoS 2 during the growth of high-κ dielectrics, highlighting O 3 -based thermal ALD as a potential route for the integration of dielectric layers on 1L MoS 2 for nanoscale optoelectronic device fabrication.