Multiscale Investigation of ZnO–Graphene Heterointerfaces: Correlating Crystallographic Disorder, Surface Chemistry, and Electrical Transport Properties

Abstract

The performance of ZnO–graphene heterointerfaces is governed by coupled phenomena spanning crystallographic defect populations, interfacial chemical bonding configurations, and electronic transport mechanisms across multiple length scales. This study establishes a multiscale characterization framework that explicitly correlates structural disorder, surface chemistry, and electrical transport in ZnO–reduced graphene oxide (rGO) heterointerfaces. Raman spectroscopy quantifies crystallographic disorder through the graphene D/G intensity ratio and ZnO phonon modes, while XPS and XAS resolve the chemical nature of interfacial bonding, revealing that hydroxide surface layers on ZnO mediate covalent coupling to functionalized graphene . Impedance spectroscopy, analyzed within equivalent circuit models comprising grain-boundary resistance and capacitance, provides direct access to charge transport mechanisms at the heterointerface, with Nyquist plot fitting revealing light-dependent relaxation processes and carrier transit times . First-principles calculations confirm that van der Waals interactions dominate at graphene–ZnO polar interfaces while charge transfer occurs due to work function differences, with the graphene Dirac point remaining intact . The multiscale framework demonstrates that interfacial hydroxide-mediated bonding, oxygen vacancy populations, and graphene defect density jointly determine the balance between efficient charge extraction and trapping-limited transport. These findings provide design criteria for heterointerface engineering in optoelectronic and energy applications.