Chemical vapor deposition of layered two-dimensional MoSi ₂ N ₄ materials

Abstract

Identifying two-dimensional layered materials in the monolayer limit has led to discoveries of numerous new phenomena and unusual properties. We introduced elemental silicon during chemical vapor deposition growth of nonlayered molybdenum nitride to passivate its surface, which enabled the growth of centimeter-scale monolayer films of MoSi2N4. This monolayer was built up by septuple atomic layers of N-Si-N-Mo-N-Si-N, which can be viewed as a MoN2 layer sandwiched between two Si-N bilayers. This material exhibited semiconducting behavior (bandgap ~1.94 electron volts), high strength (~66 gigapascals), and excellent ambient stability. Density functional theory calculations predict a large family of such monolayer structured two-dimensional layered materials, including semiconductors, metals, and magnetic half-metals.

Novel Two-Dimensional Layered MoSi2Z4 (Z = P, As): New Promising Optoelectronic Materials

“…In the calculation, norm-conserving pseudopotential, double-zeta polarization basis set and exchange-correlation functional at PBE level are employed. 3.470 Å and 3.620 Å for Z = P and As, respectively, which are well coincident with those predicted in previous work [18]. Figure 1b-d present three most likely stacking patterns of bilayer MoSi 2 Z 4 , namely AA, AB and AC, where the Si atoms in the lower layer are aligned with the Si, Z, and Mo atoms in the upper layer, respectively.…”

“…It presents A-B stacked hexagonal lattice from the top view, and its primitive cell includes one Mo atom, two Si atoms and four Z atoms as labeled by the parallelogram in Figure1a. The lattice parameters a = b = 3.470 Å and 3.620 Å for Z = P and As, respectively, which are well coincident with those predicted in previous work[18]. Figure1b-d present three most likely stacking patterns of bilayer MoSi 2 Z 4 , namely AA, AB and AC, where the Si atoms in the lower layer are aligned with the Si, Z, and Mo atoms in the upper layer, respectively.…”

“…This is different from monolayer MoSi 2 N 4 , whose CBM sits K point while VBM locates at Γ point, presenting indirect band-gap semiconducting behavior (Ref. [18], also see Figure 5a). To get more insight into this difference, PDOS and charge distribution at VBM and CBM are plotted in Figure 5c,d In terms of bilayer MoSi 2 Z 4 , similar direct bandgap semiconducting behavior to monolayer MoSi 2 Z 4 are obtained, where both CBM and VBM locate at K points (see Figure 5c,d).…”

“…Very recently, a new kind of hexagonal 2D MXene, MoSi 2 N 4 and WSi 2 N 4 , was successfully synthesized by chemical vapor deposition method with large size up to 15 mm × 15 mm [18]. They show good environmental stability, and even have no structural deformation within six months.…”

The Versatile Electronic, Magnetic and Photo‐Electro Catalytic Activity of a New 2D MA2Z4 Family**

“…in the bottom‐up synthesis of novel 2D vdW materials without known 3D parent crystals. They introduced Si as the passivating element during chemical vapor deposition (CVD) of non‐layered molybdenum nitride, which surprisingly enabled the growth of monolayer films of a new vdW 2D material, MoSi 2 N 4 [10] . The structure of MoSi 2 N 4 can be viewed as inserting a MoN 2 layer between two Si−N bilayers.…”