Journal
ACS NANO
Volume 12, Issue 6, Pages 6301-6309Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.8b03408
Keywords
two-dimensional transition metal dichalcogenide; single-layer; alloy; band gap; laser thinning; exciton complexes
Categories
Funding
- Institute for Basic Science [IBS-R011-D1]
- BK21PLUS Integrated Center for Fostering Global Creative Researcher
- Creative Materials Discovery Program through the National Research Foundation of Korea (NRF) of the Ministry of Science, the ICT and Future Planning [NRF-2015M3D1A1070672]
- Industrial Technology Innovation Program of the Ministry of Trade, Industry & Energy (MOTIE, Korea) [10080654]
- UNT SEED fund
- Korea Evaluation Institute of Industrial Technology (KEIT) [10080654] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
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Alloying two-dimensional transition metal dichalcogenides (2D TMDs) is a promising avenue for band gap engineering. In addition, developing a scalable synthesis process is essential for the practical application of these alloys with tunable band gaps in optoelectronic devices. Here, we report the synthesis of optically uniform and scalable single-layer Mo1-xWxS2, alloys by a two-step chemical vapor deposition (CVD) method followed by a laser thinning process. The amount of W content (x) in the Mo1-xWxS2 alloy is systemically controlled by the co-sputtering technique. The post-laser process allows layer-by-layer thinning of the Mo1-xWxS2 alloys down to a single-layer; such a layer exhibits tunable properties with the optical band gap ranging from 1.871 to 1.971 eV with variation in the W content, x = 0 to 1. Moreover, the predominant exciton complexes, trions, are transitioned to neutral excitons with increasing W concentration; this is attributed to the decrease in excessive charge carriers with an increase in the W content of the alloy. Photoluminescence (PL) and Raman mapping analyses suggest that the laser-thinning of the Mo1-xWxS2 alloys is a self-limiting process caused by heat dissipation to the substrate, resulting in spatially uniform single-layer Mo1-xWxS2 alloy films. Our findings present a promising path for the fabrication of large-scale single-layer 2D TMD alloys and the design of versatile optoelectronic devices.
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