Chemical
Synthetic Strategy for Single-Layer Transition-Metal
Chalcogenides
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Abstract
A solution-phase synthetic protocol
to form two-dimensional (2D)
single-layer transition-metal chalcogenides (TMCs) has long been sought;
however, such efforts have been plagued with the spontaneous formation
of multilayer sheets. In this study, we discovered a solution-phase
synthetic protocol, called “diluted chalcogen continuous influx
(DCCI)”, where controlling the chalcogen source influx
(e.g., H<sub>2</sub>S) during its reaction with the transition-metal
halide precursor is the critical parameter for the formation of single-layer
sheets as examined for the cases of group IV TMCs. The continuous
influx of dilute H<sub>2</sub>S throughout the entire growth period
is necessary for large sheet formation through the exclusive <i>a-</i> and <i>b-</i>axial growth processes. By contrast,
the burst influx of highly concentrated H<sub>2</sub>S in the early
stages of the growth process forms multilayer TMC nanodiscs. Our DCCI
protocol is a new synthetic concept for single-layer TMCs and, in
principle, can be operative for wide range of TMC nanosheets