Two-dimensional ScN with high carrier mobility and unexpected mechanical properties.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Solid State Chemistry

Background:

• Two-dimensional (2D) semiconductors are crucial for advanced electronic and optoelectronic devices due to their unique properties.
• Scandium nitride (ScN) is a promising material, but its 2D forms require theoretical investigation for potential applications.

Purpose of the Study:

• To predict and theoretically investigate novel 2D scandium nitride (ScN) structures.
• To evaluate their stability, electronic properties, and potential for electronic and optoelectronic applications.
• To explore unique mechanical properties of specific 2D ScN phases.

Main Methods:

• Utilized swarm-intelligent global structure search to predict 2D M-ScN, H-ScN, and O-ScN structures.
• Assessed material stability through calculations of formation energies and dynamical/thermal properties.
• Performed electronic structure calculations to determine bandgaps and carrier mobilities.
• Investigated mechanical properties, including Poisson's ratio and reversible strain.

Main Results:

• Successfully predicted three stable 2D ScN phases: M-ScN, H-ScN, and O-ScN.
• M-ScN and O-ScN are direct bandgap semiconductors (1.39 eV and 2.14 eV).
• H-ScN is an indirect bandgap semiconductor (3.21 eV).
• M-ScN and H-ScN exhibit ultra-high electron mobilities (3.09 × 10^4 and 1.22 × 10^4 cm^2 V^-1 s^-1).
• O-ScN demonstrates auxetic behavior (Poisson's ratio of -0.27) and ferroelasticity (15% reversible strain).

Conclusions:

• The predicted 2D ScN materials are highly feasible for experimental synthesis.
• These materials offer tunable electronic properties suitable for diverse semiconductor applications.
• O-ScN presents unique auxetic and ferroelastic characteristics, expanding its application potential beyond conventional electronics.