Growth of Ultrathin Nonlayered MnSe via CVD with Modulated Phase Competition

Two-dimensional nonlayered MnSe represent a unique class of nanomaterials that combine bulk structural characteristics with surface-dominated properties from unsaturated dangling bonds. However, their specific phase control remains fundamentally challenging due to inherent thermodynamic instabilities. Herein, we report the successful fabrication of ultrathin wurtzite-type and rock-salt-type MnSe nanosheets via chemical vapor deposition (CVD) by modulating growth parameters. In addition, we carried out density functional theory (DFT) and thermodynamic analysis to systematically elucidate the formation mechanisms of diverse crystalline phases during crystal growth, revealing that this polymorphic behavior stems from intrinsic thermodynamic competition. Notably, wurtzite-type MnSe exhibits unique optical properties, including a distinct photoluminescence (PL) emission feature at 900 nm (1.38 eV), caused by impurity-perturbed Mn2+ excitons. This study provides fundamental insights into phase control in nonlayered 2D materials, paving the way for their integration into electronic, optoelectronic, and spintronic devices.