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Monolayer Tungsten Disulfide (WS 2 ) via Chlorine‐Driven Chemical Vapor Transport
Author(s) -
Modtland Brian J.,
NavarroMoratalla Efren,
Ji Xiang,
Baldo Marc,
Kong Jing
Publication year - 2017
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201701232
Subject(s) - tungsten disulfide , chemical vapor deposition , monolayer , materials science , halide , photoluminescence , tungsten , physical vapor deposition , crystal (programming language) , crystal growth , evaporation , inorganic chemistry , chemical engineering , nanotechnology , thin film , chemistry , optoelectronics , crystallography , metallurgy , physics , computer science , engineering , thermodynamics , programming language
Large‐scale production of high‐quality tungsten disulfide (WS 2 ) monolayers is a prerequisite for potential device applications using this promising transition metal dichalcogenide semiconductor. The most researched technique is chemical vapor deposition, typically involving the reaction of sulfur vapors with tungsten oxide. Other techniques such as physical vapor deposition have been explored with some success, but low vapor pressures make growth difficult. This study demonstrates a growth process that relies on halide‐driven vapor transport commonly utilized in bulk crystal growth. Using a small amount of sodium chloride salt as a source of chlorine, nonvolatile WS 2 can react to form gaseous tungsten chloride and sulfur. With an open tube system, a controlled reaction generates mono and few‐layer WS 2 crystals. Optical and physical characterization of the monolayer material shows good uniformity and triangular domains over 50 µm in length. Photoluminescence transient measurements show similar nonlinear exciton dynamics as exfoliated flakes, attributed to multiparticle physics. Requiring only the powder of the desired crystal and appropriate halide salt as precursors, the technique has the potential to realize other layered materials that are challenging to grow with current processes.