Nucleation and Growth of WSe₂: Enabling Large Grain Transition Metal Dichalcogenides


The limited grain size (< 200 nm) for transition metal dichalcogenides (TMDs) grown by molecular beam epitaxy (MBE) reported in the literature thus far is unsuitable for high-performance device applications. In this work, the fundamental nucleation and growth behavior of WSe₂ is investigated through a detailed experimental design combined with on-lattice, diffusion-based first principles kinetic modeling to enable large area TMD growth. A three-stage adsorption-diffusion-attachment mechanism is identified and the adatom stage is revealed to play a significant role in the nucleation behavior. To limit the nucleation density and promote 2D layered growth, it is necessary to have a low metal flux in conjunction with an elevated substrate temperature. At the same time, providing a Se-rich environment further limits the formation of W-rich nuclei which suppresses vertical growth and promotes 2D growth. The fundamental understanding gained through this investigation has enabled an increase of over one order of magnitude in grain size for WSe₂ thus far, and provides valuable insight into improving the growth of other TMD compounds by MBE and other growth techniques such as chemical vapor deposition (CVD).



Tungsten diselenide, transition metal dichalcogenides, van der waals epitaxy, nucleation and growth, kinetic monte carlo simulation, Field-effect transistors, Molecular beam epitaxy, Scanning tunneling microscopy, Epitaxy, Thin films, Semiconductors, Molybdenum disulfide, Tungsten(IV) Selenide, Selenium, Monte Carlo method

NSF Award No. 1407765; National Research Foundation of Korea no. 2013K1A4A3055679


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