In recent years, there have been tremendous advancements in the growth of monolayer transition metal dichalcogenides (TMDCs) by chemical vapor deposition (CVD). However, obtaining high photoluminescence quantum yield (PL QY), which is the key figure of merit for optoelectronics, is still challenging in the grown monolayers. Specifically, the as-grown monolayers often exhibit lower PL QY than their mechanically exfoliated counterparts. In this work, we demonstrate synthetic tungsten diselenide (WSe 2 ) monolayers with PL QY exceeding that of exfoliated crystals by over an order of magnitude. PL QY of ∼60% is obtained in monolayer films grown by CVD, which is the highest reported value to date for WSe 2 prepared by any technique. The high optoelectronic quality is enabled by the combination of optimizing growth conditions via tuning the halide promoter ratio, and introducing a simple substrate decoupling method via solvent evaporation, which also mechanically relaxes the grown films. The achievement of scalable WSe 2 with high PL QY could potentially enable the emergence of technologically relevant devices at the atomically thin limit.
Bibliographical noteFunding Information:
Materials growth, characterization, and modeling were supported by the Electronic Materials Program funded by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division of the U.S. Department of Energy, under contract no. DE-AC02- 05CH11231. Electron microscopy was performed at the Molecular Foundry, which was supported by the Office of Science, Office of Basic Energy Sciences of the U.S. Department of Energy under contract no. DE-AC02-05CH11231. H.K. acknowledges the support from a Samsung Scholarship. A.J. acknowledges the support from Lam Research.
Copyright © 2019 The Authors.
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