Gate-Tunable In-Plane Ferroelectricity in Few-Layer SnS.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Ultrathin ferroelectric materials are crucial for miniaturized electronic devices like sensors and memory.
• The intrinsic depolarization field typically destabilizes polarization in ultrathin ferroelectric films.
• Developing stable ultrathin ferroelectrics is essential for next-generation electronics.

Purpose of the Study:

• To investigate robust in-plane ferroelectricity in few-layer tin sulfide (SnS) 2D crystals.
• To understand the coupling between ferroelectricity and lattice strain in SnS.
• To demonstrate ferroelectric switching in SnS-based field-effect transistors.

Main Methods:

• Fabrication of field-effect transistor devices using ultrathin SnS films.
• Characterization of in-plane ferroelectricity and its dependence on lattice strain.
• Analysis of the layer-dependent nanoripple formation and its relation to inversion symmetry.

Main Results:

• Robust in-plane ferroelectricity was observed in few-layer SnS 2D crystals.
• Anisotropic coupling between polarization and lattice strain was identified.
• SnS exhibits nanoripples along the armchair direction due to a converse piezoelectric effect.
• An odd-and-even layer-dependent effect in nanoripples indicates sensitivity to inversion symmetry.
• Successful ferroelectric switching was demonstrated in SnS-based field-effect transistors, with enhanced response at negative gate voltages.

Conclusions:

• Few-layer SnS 2D crystals exhibit stable in-plane ferroelectricity, overcoming common ultrathin film limitations.
• The unique strain-coupled ferroelectricity and layer-dependent effects in SnS offer new avenues for device design.
• SnS shows significant potential for applications in ultrathin ferroelectric field-effect transistors and nanoscale electromechanical systems.