posted on 2021-03-22, 19:05authored bySyed Hamza Safeer, Marcus V. O. Moutinho, Arthur R. J. Barreto, Braulio Soares Archanjo, Omar Ginoble Pandoli, Marco Cremona, Marcelo Eduardo Huguenin Maia da Costa, Fernando Lazaro Freire, Victor Carozo
Monolayers
of molybdenum disulfide are of vital importance in the
fabrication of optical and nanoelectronic devices. The development
of thin and low-cost devices has increased the demand for synthesis
processes. Usually, the synthesis of molybdenum disulfide monolayers
requires temperatures of approximately 800 °C, which is a drawback
for the applications mentioned above. Here, we propose a route using
the atmospheric pressure chemical vapor deposition technique to grow
monolayers of MoS2 at 550 °C mediated by using sodium
as a catalyst. We produced single crystals and polycrystalline films
by controlling the NaNO3/MoO3 catalyst/precursor
ratio and the growth time. Using first-principles calculations, we
determined that sodium was the nucleation site of the growth process.
The precursor’s ratio is crucial to decrease the formation
energy and the synthesis temperature. First-principles calculations
and experiments showed that the ideal precursor ratio was 0.3 and
that the synthesis temperature should be decreased by 250 °C.
We investigated the monolayers with optical microscopy, high-resolution
scanning transmission electron microscopy, X-ray photoelectron spectroscopy,
atomic force microscopy, Raman spectroscopy, photoluminescence spectroscopy,
and transport experiments. The optical and electrical performances
were comparable to those of monolayers grown at higher temperatures.
We believe that a low-temperature synthesis recipe is essential to
drive the fabrication of nanoscale optoelectronic devices.