Critical curvature localization in graphene. II. Non-local flexoelectricity-dielectricity coupling

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Flexoelectricity, the induction of polarization by mechanical strain gradients, is a key property in dielectric materials.
• Multi-layered graphene (MLG) exhibits unique electromechanical behaviors influenced by structural features like crinkles.
• Understanding molecular adsorption on surfaces like highly oriented pyrolytic graphite (HOPG) is crucial for nanoscale applications.

Purpose of the Study:

• To establish a general thermodynamic framework for flexoelectric constitutive laws in MLG.
• To elucidate the role of surface crinkles in the molecular adsorption characteristics of HOPG.
• To develop and validate a non-local interaction model for flexoelectric polarization in MLG.

Main Methods:

• Development of a thermodynamically consistent flexoelectric constitutive framework for MLG.
• Application of a non-local interaction model to predict polarization and curvature localization.
• Validation of the model using density functional theory (DFT) calculations and comparison with existing local models.

Main Results:

• The non-local flexoelectric model accurately predicts polarization localization at crinkle valleys and ridges.
• Calibrated layer-number-dependent dielectric and flexoelectric coefficients for MLG were formulated.
• DFT analysis revealed that polarization-induced adsorption of neutral molecules at crinkle ridges is dependent on molecular weight, explaining C60 buckyball self-organization.

Conclusions:

• The developed non-local flexoelectric model provides a robust explanation for peculiar molecular adsorption phenomena on crinkled graphite surfaces.
• The study successfully links microscopic flexoelectric effects in MLG to macroscopic adsorption behaviors.
• This work offers insights into the self-organized adsorption of molecules like C60 buckyballs on HOPG surfaces.