Analytical study of morphology-related defects in epitaxial graphene for high-performance application*

Large-scale of homogeneous high-quality graphene can be achieved by epitaxial growth on a silicon carbide substrate [1], offering a promising opportunity for commercialization of graphene-based devices including the quantum Hall resistance standard [2], highly sensitive photodetectors [3], Hall effect sensors [4] etc.

The quality of epitaxial graphene is critical for the performance of graphene devices and is mainly affected by morphology-related defects such as terrace-structure formed on the silicon carbide surface during the growth process and the multilayer graphene along the step edge of the terraces. In this work, we investigated the scattering lengths related to the terrace structure and the multilayer graphene in epitaxial graphene. We prepared epitaxial graphene samples with surface terraces of width varying from less than 1 micronmeter to more than 10 micrometers. The multilayer graphene coverage ratio of these samples varies from 0% to 10%. By functionalizing graphene with Cr(CO)₃ [5] and through a vacuum annealing process, we can tune its carrier density, which allows us to study the transport properties of the graphene devices in a wide range of carrier density. We analyzed weak localization and weak antilocalizaion effects to extract the scattering lengths in epitaxial graphene and correlated the results to the device performance which is evaluated by precision measurement of the quantized Hall resistance at v=2 plateau.