Control of 2D Crystal Monodispersity through a Seeded Growth Approach

Achieving the synthesis of uniform two-dimensional (2D) transition metal dichalcogenide (TMD) crystals through chemical vapor deposition (CVD) is a sought after goal for enabling their use in future transistor, memory, and optics applications. Here, we demonstrate a seeded growth strategy that yields size monodisperse 2D TMD monolayers via CVD synthesis from pre-etched Mo oxide precursors. Controlled etching of MoO3 particles in NaOH solution produces well-defined nucleation reservoirs that take part in subsequent reactions with Se to form monodisperse 2D MoSe2 crystals. Crystal sizes are controllable by the particle etching time and the CVD reaction time down to a few hundred nanometers with size variations as low as 1.8%. Electron microscopy and Raman and photoluminescence spectroscopies verify the structural and optical quality of the as-grown MoSe2 crystals. This study reinforces the enduring need for advances in synthesis-driven control of the size, morphology, composition, and strain- and defect-states of 2D materials.