Granular metals with SiN x dielectrics

Abstract

Understanding and controlling nanoscale interface phenomena, such as band bending and secondary phase formation, is crucial for electronic device optimization. In granular metal (GM) studies, where metal nanoparticles are embedded in an insulating matrix, the importance of interface phenomena is frequently neglected. We demonstrate that GMs can serve as an exemplar system for evaluating the role of secondary phases at interfaces through a combination of x-ray photoemission spectroscopy (XPS) and electrical transport studies. We investigated SiN_xas an alternative to more commonly used oxide-insulators, as SiN_x-based GMs may enable high temperature applications when paired with refractory metals. Comparing Co-SiN_xand Mo-SiN_xGMs, we found that, in the tunneling-dominated insulating regime, Mo-SiN_xhad reduced metal-silicide formation and orders-of-magnitude lower conductivity. XPS measurements indicate that metal-silicide and metal-nitride formation are mitigatable concerns in Mo-SiN_x. Given the metal-oxide formation seen in other GMs, SiN_xis an appealing alternative for metals that readily oxidize. Furthermore, SiN_xprovides a path to metal-nitride nanostructures, potentially useful for various applications in plasmonics, optics, and sensing.

Keywords: STEM; XPS; electron tunneling; granular metals; interface phenomena.