Understanding metal organic chemical vapour deposition of monolayer WS<sub>2</sub>: the enhancing role of Au substrate for simple organosulfur precursors.
Veigang-Radulescu, Vlad P
Stewart, J Callum
Swallow, Jack EN
Alexander-Webber, Jack Allen
Pollard, Andrew J
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Fan, Y., Nakanishi, K., Veigang-Radulescu, V. P., Mizuta, R., Stewart, J. C., Swallow, J. E., Dearle, A. E., et al. (2020). Understanding metal organic chemical vapour deposition of monolayer WS<sub>2</sub>: the enhancing role of Au substrate for simple organosulfur precursors.. Nanoscale, 12 (43), 22234-22244. https://doi.org/10.1039/d0nr06459a
We find that the use of Au substrate allows fast, self-limited WS2 mono-layer growth using a simple sequential exposure pattern of low cost, low toxicity precursors, namely tungsten hexacarbonyl and dimethylsulfide (DMS). We use this model reaction system to fingerprint the technologically important metal organic chemical vapour deposition process by operando X-ray photoelectron spectroscopy (XPS) to address the current lack of understanding of the underlying fundamental growth mechanisms for WS2 and related transition metal dichalcogenides. Au effectively promotes the sulfidation of W with simple organosulfides, enabling WS2 growth with low DMS pressure (<1 mbar) and a suppression of carbon contamination of as-grown WS2, which to date has been a major challenge with this precursor chemistry. Full WS2 coverage can be achieved by one exposure cycle of 10 minutes at 700°C. We discuss our findings in the wider context of previous literature on heterogeneous catalysis, 2D crystal growth, and overlapping process technologies such as atomic layer deposition (ALD) and direct metal conversion, linking to future integrated manufacturing processes for transition metal dichalcogenide layers.
We acknowledge funding from EPSRC (EP/T001038/1, EP/P005152/1). V.-P.V.-R. acknowledges EPSRC Doctoral Training Award (EP/M508007/1) and support from NPL. K.N. and R. M. acknowledge funding from the EPSRC Cambridge NanoDTC (Grant No. EP/G037221/1). B.B. and A.J.P. acknowledge funding from the U.K. Department of Business, Energy and Industrial Strategy (NPL Project Number 121452). J.A.-W. acknowledges the support of his Research Fellowship from Royal Commission for the Exhibition of 1851, and Royal Society Dorothy Hodgkin Research Fellowship. Y.F. also thanks Prof. Wencai Ren for the helpful discussions on the effect of pre-annealing of gold to CVD WS2. This work was carried out with the support of the Diamond Light Source, instrument B07-C (proposal SI-22123).
National Physical Laboratory (NPL) (unknown)
Royal Commission for the Exhibition of 1851 (RF474/2016)
Royal Society (DHF\F1\191163)
Engineering and Physical Sciences Research Council (EP/S019367/1)
Engineering and Physical Sciences Research Council (EP/R00661X/1)
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External DOI: https://doi.org/10.1039/d0nr06459a
This record's URL: https://www.repository.cam.ac.uk/handle/1810/312242
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