| AVS 59th Annual International Symposium and Exhibition | |
| Oxide Heterostructures-Interface Form & Function Focus Topic | Monday Sessions |
| Session OX+EM+MI+NS+TF-MoM |
| Session: | Structure–Property Relationships in Epitaxial Oxide Interfaces |
| Presenter: | S.R. Cohen, Weizmann Institute of Science, Israel |
| Authors: | K. Gotlib-Vainshtein, Bar Ilan University, Israel O. Girshevitz, Bar Ilan University, Israel C.N. Sukenik, Bar Ilan University, Israel D. Barlam, Ben Gurion University, Israel E. Kalfon-Cohen, Weizmann Institute of Science, Israel S.R. Cohen, Weizmann Institute of Science, Israel |
| Correspondent: | Click to Email |
The design of surfaces with controlled stiffness is attractive for a variety of applications ranging from controlling cell growth to mechanical and electrical engineering design. Here, the creation of layered composites with tunable surface stiffness has been achieved by coating a soft PDMS polymer with a stiff film of amorphous titanium oxide with thickness varying from 2 to 50 nm. The oxide layer is smooth (6 nm rms roughness at 2 µm2 image size), and crack-free. Air plasma treatment was used to form a silica surface layer on the soft polymer base to promote of adhesion of the titania overlayer. To gain insight into the mechanics of the layered structure, nanomechanical quantification has been performed using different experimental approaches, as well as modeling studies. The surface mechanical properties of the samples have been probed using both instrumented nanoindentation and atomic force microscopy—based nanomechanical characterization. These results have been compared to finite element analysis (FEA) simulations.
By fitting the FEA simulations with experimental curves it is shown that the hard titania film and softer PDMS substrate individually maintain their characteristic elastic moduli, while the stiffness of the vertical nanocomposite can be controllably modified by changing the thickness of the stiff layer. Liquid phase deposition of the oxide allows control of its thickness at the nm level. During an indentation cycle, the stiff layer transmits the stress to the underlying PDMS base by deformation of its overall shape, but only negligible compression of the film thickness.
This synthetic approach can be quite versatile, and can, in principle, be extended to different oxides and a wide range of thicknesses. It allows control of surface properties while maintaining bulk material properties. This exploratory work is a first step towards defining the range of surface stiffnesses that can be achieved in this way, as well as developing general methodologies for their characterization.