Surface elasticity and surface slice thickness effects on the elastic properties of nanofilms

A formula for size-dependent Young's modulus was obtained by considering surface elasticity effect and surface slice thickness effect. Due to the influence of surface slice thickness, the second and third surface modifications, i.e., nonlinear surface modifications were introduced. The first surface modification, i.e., the linear surface modification of Young's modulus is induced by surface elastic coefficient and nonlinear surface modifications are induced by surface slice thickness. For given surface Young's modulus Y-s, surface slice thickness strongly enhanced surface effect; while for given surface elastic coefficient S, surface slice thickness weakened surface effect. The influence of surface slice thickness effect on nanofilm effective Young's modulus is more obviously in the condition that the surface slice thickness is comparable with film thickness, the film with only several nanometers or with oxidated surface for example. The present theoretical scheme is envisaged to provide helpfulness for further research of mechanical properties of nanofilms and useful insights for designing and application of nanofilm-based devices.