Interfacial control for uniformly depositing oxide dielectrics in top-gate graphene field-effect transistors

The distinctive surface characteristics of two-dimensional(2D) materials present a significant challenge when developing heterostructures for electronic or optoelectronic devices. In this study, we present a method for fabricating top-gate graphene field-effect transistors (FETs) by incorporating a metal interlayer between the dielectric and graphene. The deposition of an ultrathin Ti layer facilitates the formation of a uniform HfO₂ layer on the graphene surface via atomic layer deposition (ALD). During the ALD process, the Ti layer oxidizes to TiO₂, which has a negligible impact on the current flow along the graphene channel. The mobility of graphene in the FET was enhanced in relation to the SiO₂-based back-gate FET by modifying the thin HfO₂ top-gate dielectric deposited on the Ti interlayer. Furthermore, shifts in the Dirac point and subthreshold swing were markedly reduced owing to the reduction in charge scattering caused by the presence of trap sites at the interface between graphene and SiO₂. This route to modulating the interface between 2D material-based heterostructures will provide an opportunity to improve the performance and stability of 2D electronics and optoelectronics.