Influence of surface stresses on indentation response.

Area of Science:

• Materials Science
• Surface Physics
• Computational Materials Science

Background:

• Surface stresses influence the effective elastic constants of thin films and surfaces.
• Modern scanning probe techniques enable measurements at the nanoscale where these effects are significant.

Purpose of the Study:

• To computationally investigate the impact of surface stresses on the elastic behavior of thin films.
• To compare Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations for calculating surface elastic properties.
• To develop models for understanding surface stress effects in indentation experiments.

Main Methods:

• Employed a multiscale computational approach combining DFT and MD simulations.
• Calculated surface elastic constants for silicon and strontium titanate.
• Developed a continuum finite-element multilayer model incorporating DFT-derived surface elastic constants.
• Proposed and validated an analytical model for indentation modulus as a function of contact radius.

Main Results:

• Surface stresses induce a reduction in the indentation modulus for both silicon and strontium titanate.
• This reduction was approximately 5% for strontium titanate and 6% for silicon at a contact radius of [Formula: see text].
• The analytical model accurately predicted simulation results for both spherical and flat punch indenters.
• The impact of surface stress on indentation modulus was found to be independent of indenter shape for the studied conditions.

Conclusions:

• Surface stresses play a crucial role in the mechanical response of thin films and surfaces.
• The developed multiscale and analytical models provide accurate predictions of indentation behavior under surface stress effects.
• These findings are relevant for nanoscale material characterization and device design involving thin films.