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 MoO 3 particles in NaOH solution produces well-defined nucleation reservoirs that take part in subsequent reactions with Se to form monodisperse 2D MoSe 2 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 MoSe 2 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.