Passivation of Defects in Macroscopic Graphene Sheets Via Selective Atomic Layer Deposition of Metal Oxides

Abstract

Graphene, with its high conductivity, specific surface area, and overall chemical inertness, has been heavily researched for applications in batteries, supercapacitors, and water-splitting devices. While graphene films can be synthesized over large areas (>1 cm2) through chemical vapor deposition, graphene generated through this route exhibits a high defect density that can inhibit performance and stability in electrochemical systems. Considerable effort has been devoted to passivating, repairing, and remediating these defects for graphene-based devices to match their theoretical potential. To this end, we have developed new atomic layer deposition (ALD) processes designed to selectively passivate high energy defect sites with metal oxides. This deposition chemistry targets dangling bonds and oxidized regions on the graphene sheet based on their higher reactivity relative to the pristine basal plane. We have also demonstrated analogous chemistry on bulk highly-ordered pyrolytic graphite as well as exfoliated few-layer graphene. The efficacy of the deposition process was examined as a function of precursor dose and temperature. The selectivity of this process and metal-oxide layer thicknesses was assessed using several electron microscopy techniques. This work further illustrates an effective scheme to ameliorate the interfacial chemistry of large-area graphene and demonstrate how targeted passivation can improve device performance.