The effect of growth temperature and metal-to-chalcogen on the growth of WSe2 by molecular beam epitaxy

Peter M. Litwin; Maria Gabriela Sales; Victoria Nilsson; Prasanna V. Balachandran; Costel Constantin; Stephen McDonnell

doi:10.1117/12.2530454

9 September 2019 The effect of growth temperature and metal-to-chalcogen on the growth of WSe₂ by molecular beam epitaxy

Peter M. Litwin, Maria Gabriela Sales, Victoria Nilsson, Prasanna V. Balachandran, Costel Constantin, Stephen McDonnell

Author Affiliations +

Proceedings Volume 11085, Low-Dimensional Materials and Devices 2019; 110850U (2019) https://doi.org/10.1117/12.2530454
Event: SPIE Nanoscience + Engineering, 2019, San Diego, California, United States

Abstract

To further the present understanding of growth conditions on the quality of transition metal dichalcogenide (TMDC) thin films grown by molecular beam epitaxy (MBE), we study the effect of growth temperature and chalcogento- metal flux ratio on the chemical composition and surface morphology of synthesized WSe2 thin films. In-situ X-ray photoelectron spectroscopy (XPS) is performed to analyze the intrinsic chemical composition of the grown material prior to atmospheric exposure and ex-situ atomic force microscopy (AFM) is employed to study the surface morphology of grown, sub-monolayer films. We find that both low and high growth temperature ranges can be detrimental to the chemical homogeneity of the grown material and that these results are echoed in the resulting grain morphology. Growing at 375 °C resulted in the formation of metastable 1T’-WSe₂ alongside the thermodynamically stable 2H phase. Thin films grown at 750 °C resulted in the formation of highly Se deficient material. An intermediate growth temperature of 565 °C produced the most chemically homogeneous films above a critical chalcogen to metal flux ratio of 3250:1. Density functional theory calculations are used to rationalize the insights gained from the measured XPS data. Especially, the influence of Se-vacant WSe_2-x monolayers is explored and its impact on the coordination environment around the Se-atoms is used to interpret the measured XPS data.

Citation Download Citation

Peter M. Litwin, Maria Gabriela Sales, Victoria Nilsson, Prasanna V. Balachandran, Costel Constantin, and Stephen McDonnell "The effect of growth temperature and metal-to-chalcogen on the growth of WSe₂ by molecular beam epitaxy", Proc. SPIE 11085, Low-Dimensional Materials and Devices 2019, 110850U (9 September 2019); https://doi.org/10.1117/12.2530454

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