Chemical vapor deposition of layered two dimensional MoSi2N4 materials
Stabilizing monolayer nitrides with silicon Transition metal carbides and nitrides are nonlayered materials that in monolayer form have potentially useful electronic and chemical properties. These monolayers are usually made by chemical etching that produces flakes with surface defects that have poor air and water stability. Hong et al. report that introducing silicon during chemical vapor deposition growth of molybdenum nitride passivates the surface and prevents island formation. Centimeter scale monolayer films of the semiconductor MoSi2N4 form as a MoN2 layer sandwiched by two Si N bilayers. These layers possess high mechanical strength and ambient stability. Science, this issue p. 670 Addition of silicon during film growth stabilized a molybdenum nitride monolayer by sandwiching it between two Si N bilayers. 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.
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