Modifying the platinum-hafnia and copper-hafnia interface using an organophosphonate nanolayer

Abstract

This study demonstrates the ability of organophosphonate nanomolecular layers (NMLs) to modify the interfacial fracture toughness of the Pt/HfO2 and Cu/HfO2 interfaces. In the cases of the Pt/HfO2 interfaces the inclusion of a NML lead to at least a two-fold enhancement in fracture energy. In contrast, including these NMLs at Cu/HfO2 interfaces decreases fracture energy seen for untreated interfaces by a factor of at least 2. Different molecules with identical chemical termini but varying chain length were utilized in order to test the effect of molecular length on the fracture energy. These results show that increasing molecular length decreases fracture energy. Analyses of core-level spectra from the fracture surfaces indicate that Pt/NML/HfO2 interfaces delaminate at the Pt-S bonds and the Cu/NML/HfO2 interfaces at least partially delaminate at the Cu-Cu bonds. This study shows that NMLs can be used to modify the fracture strength of interfaces for use in a variety of applications.