7:43 PM - NM07.05.13
Salt-Assisted Growth of 2D Transition Metal Dichalcogenides
Shisheng Li1
National Institute for Materials Science1
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Abstracts
Chemical vapor deposition (CVD) of 2D transition metal dichalcogenides (TMDCs) always involves the conversion of vapor precursors to solid products in a vapor-solid-solid (VSS) growth mode (e.g., WO3 + S → WS2 + SO2). This often requires very high temperatures to sublimate metal oxide precursors (e.g., WO3).
Our pioneering work on salt-assisted CVD (Salt 1.0 technique) enables the growth of 2D WS2 and WSe2 monolayers in a mild condition (lower temperature and atmospheric pressure) [1,2]. In the last five years, the use of alkali (alkaline earth) metal halides (AH, A = Li, Na, K, Ba, Ca; H = F, Cl, Br, I) in CVD has demonstrated great success in growing tens of atomically thin metal chalcogenides, graphene & h-BN monolayers [3,4]. This is due to the formation of volatile MOuClv and non-volatile NaMyOz when alkali (alkaline earth) metal halides react with metal oxides. They are highly efficient precursors for growing 2D TMDC monolayers.
The recent discovery and use of non-volatile molten salts in CVD (Salt 2.0 technique) trigger the vapor-liquid-solid (VLS) growth of 1D/2D TMDC monolayers [5]. The Salt 2.0 technique shows great improvements in the high-efficient and reproducible growth of large-area, uniform, and high-quality 2D TMDC monolayers. The Salt 2.0 technique also demonstrates great potentials in growing 2D TMDC materials in the following aspects: wafer-scale single crystals, patterns, heterostructure, and alloys [6]. It represents a new trend in the CVD growth of 2D TMDC materials.
References
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[6] S. Li, Y.-C. Lin, X.-Y. Liu, Z. Hu, J. Wu, H. Nakajima, S. Liu, T. Okazaki, W. Chen, T. Minari, Y. Sakuma, K. Tsukagoshi, K. Suenaga, T. Taniguchi and M. Osada, Nanoscale 11 16122 (2019).