Research Highlights

Atomic vs. sub-atomic layer deposition: impact of growth rate on the optical and structural properties of MoS₂ and WS₂

Christian Tessarek, Tim Grieb, Florian F Krause, Christian Petersen,  Alexander Karg, Alexander Hinz, Niels Osterloh, Christian Habben, Stephan Figge, Jon-Olaf Krisponeit, Thomas Schmidt,  Jens FaltaAndreas RosenauerMartin Eickhoff

2D Materials 11(2) (2024): 025031

DOI: 10.1088/2053-1583/ad3134

MoS2 and WS2 mono- and multilayers were grown on SiO2/Si substrates. Growth by atomic layer deposition (ALD) at fast growth rates is compared to sub-ALD, which is a slow growth rate process with only partial precursor surface coverage per cycle. A Raman spectroscopic analysis of the intensity and frequency difference of the modes reveals different stages of growth from partial to full surface layer coverage followed by layer-by-layer formation. The initial layer thickness and structural quality strongly depend on the growth rate and monolayers only form using sub-ALD. Optical activity is demonstrated by photoluminescence (PL) characterization which shows typical excitonic emission from MoS2 and WS2 monolayers. A chemical analysis confirming the stoichiometry of MoS2 is performed by x-ray photoelectron spectroscopy. The surface morphology of layers grown with different growth rates is studied by atomic force microscopy. Plan-view transmission electron microscopy analysis of MoS2 directly grown on freestanding graphene reveals the local crystalline quality of the layers, in agreement with Raman and PL results.

Atomic vs. sub-atomic layer deposition: impact of growth rate on the optical and structural properties of MoS2 and WS2 article picture
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