Anisotropic polarization-induced conductance at a ferroelectric-insulator interface

Area of Science:

• Condensed Matter Physics
• Materials Science
• Oxide Heterostructures

Background:

• Emergent phenomena in complex oxide heterostructures arise from coupled degrees of freedom (charge, spin, orbital, lattice).
• Two-dimensional electron gases (2DEGs) form at polar/non-polar interfaces like LaAlO3/SrTiO3 due to polar discontinuity.
• Ferroelectric polarization at interfaces can also induce polar discontinuities, potentially forming 2DEGs or two-dimensional hole gases (2DHGs).

Purpose of the Study:

• To experimentally investigate the formation of ferroelectrically induced interfacial two-dimensional electron gases (2DEGs).
• To explore the relationship between ferroelectric polarization orientation and interfacial conductivity.
• To provide evidence for polarization-induced doping at ferroelectric/insulator interfaces.

Main Methods:

• Fabrication and characterization of BiFeO3-TbScO3 (BFO/TSO) (001) heterostructures.
• Probing local conductance and ferroelectric polarization across the heterostructure cross-section.
• Utilizing electron energy-loss spectroscopy and theoretical modeling.

Main Results:

• Observed strongly anisotropic polarization-induced conductivity at the BFO/TSO interface.
• Demonstrated conductivity along 109° domain stripes in BFO, with insulating behavior perpendicular to them.
• Evidence suggests alternating polarization within ferroelectric domains causes anisotropic electron or hole doping.

Conclusions:

• The study provides the first experimental evidence of a ferroelectrically induced interfacial 2DEG with anisotropic conductivity.
• The findings highlight the role of ferroelectric domain structure in controlling interfacial electronic properties.
• This work opens avenues for designing novel electronic devices based on ferroelectric heterostructures.