Germanether: a two-dimensional auxetic semiconductor with tunable direct-band-gap and high electron mobility

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Pristine germanene, a zero-gap semi-metal, presents limitations for semiconducting device applications.
• Developing novel two-dimensional (2D) materials with tunable electronic properties is crucial for advanced technologies.

Purpose of the Study:

• To theoretically design and investigate a new 2D material, germanether, with potential for nanoelectronic and nanomechanical applications.
• To explore the electronic, mechanical, and stability properties of the proposed germanether structure.

Main Methods:

• First-principles calculations were employed to study the structural, electronic, and mechanical properties of germanether.
• Dynamical and thermal stability were assessed.
• The effects of uniaxial strain and layer stacking on the band gap were investigated.

Main Results:

• Germanether was theoretically designed, exhibiting excellent dynamical and thermal stability.
• The material possesses an indirect band gap of 1.37 eV and high electron mobility (2.32 × 10^3 cm^2 V^-1 s^-1).
• Uniaxial strain and stacking order can induce an indirect-to-direct band gap transition.
• Remarkable in-plane negative Poisson's ratios (auxetic behavior) were observed, attributed to unique Ge-O tetrahedron symmetry and Ge-4d orbital interactions.

Conclusions:

• Germanether is a promising 2D material with a tunable band gap and excellent electron mobility.
• Its auxetic properties, distinct from other reported materials, open new avenues in nanomechanics.
• Germanether presents a competitive candidate for future applications in nanoelectronics and nanomechanics.