Anomalous ionic conduction in ferroelectric semiconductor junctions comprising multistate CuInP₂S₆

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Van der Waals ferroelectric CuInP2S6 (CIPS) shows promise for multifunctional electronics due to its multiple polarization states and Cu+ ion migration.
• The coupling of ferroelectric polarization and ion migration, termed 'ferroionic' behavior, offers a new pathway for advanced devices.

Purpose of the Study:

• Investigate the interplay between ferroelectric polarization and ionic migration in n++-Si/CIPS/MoS2 ferroelectric semiconductor junction (FSJ) devices.
• Explore how distinct polarization states influence memristive and rectifying electronic behaviors.

Main Methods:

• High-resolution piezoresponse force microscopy (PFM) and conductive atomic force microscopy (c-AFM) imaging and spectroscopy.
• Fabrication and characterization of n++-Si/CIPS/MoS2 ferroelectric semiconductor junction (FSJ) devices.

Main Results:

• Distinct dual and quadruple polarization states were observed in the FSJ devices.
• Dual-polarization FSJs demonstrated voltage- and frequency-dependent current-voltage hysteresis (memristive behavior).
• Quadruple-polarization FSJs achieved a rectification ratio exceeding 10^4, linked to Cu+ ion migration and polarization modulation.

Conclusions:

• Ferroelectric-ionic coupling in CIPS-based FSJs can be leveraged to achieve multifunctional device performance.
• Interfacial engineering in these ferroelectric semiconductor junctions offers a strategy for developing non-volatile memories and neuromorphic computing applications.