Enhanced flexoelectricity at reduced dimensions revealed by mechanically tunable quantum tunnelling

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Flexoelectricity describes the polarization of dielectrics under strain gradients, a universal electromechanical coupling.
• Nanoscale flexoelectricity offers potential for novel phenomena and functions, but requires robust characterization techniques.

Purpose of the Study:

• To develop and demonstrate a novel method for characterizing nanoscale flexoelectricity.
• To investigate the flexoelectric properties of ultrathin strontium titanate (SrTiO3) films.

Main Methods:

• Utilizing an atomic force microscope (AFM) tip to apply controlled strain gradients to ultrathin SrTiO3 films.
• Simultaneously measuring quantum tunnel current across the polarized film to detect changes in the tunnel barrier profile.

Main Results:

• Observed critical behavior in tunnel current as a function of applied strain gradients, indicating significant flexoelectric polarization.
• Demonstrated substantial modification of tunnel barrier profiles due to nanoscale flexoelectricity.
• Quantified significantly enhanced flexocoupling strength in ultrathin SrTiO3 compared to bulk, highlighting nanoscale effects.

Conclusions:

• Nanoscale flexoelectricity is more potent in ultrathin films like SrTiO3.
• The developed method enables reliable characterization of nanoscale flexoelectricity.
• This research opens avenues for applications in dynamic mechanical control of quantum effects and nanoscale devices.