Direct synthesis of graphene quantum dots on hexagonal boron nitride substrate

Abstract

We report the fabrication and characterization of large-scale graphene quantum dots (GQDs) grown on hexagonal boron nitride (h-BN) substrates with different layers and similar size of island diameters. The GQDs on h-BN synthesized by chemical vapor deposition (CVD) exhibit excellent morphology, unambiguous interfaces and well-ordered arrangement. These characteristics were achieved by adjusting the control parameters in the growth process, including the gas flow rate, temperature and pressure. The synthesized GQDs were shown to possess a thickness-dependent photoluminescence (PL) feature. Broad and red-shift emission features in monolayer GQDs suggest that the inhomogeneity of the surfaces, shapes and edges in the quantum dots of the nearby one-layer thickness sensitively affect the PL spectra. However, the GQDs with a thickness of more than 10 layers emit very sharp PL spectra with nearly identical shape and position independent of the excitation wavelength. The results suggest routes towards creating large-scale optoelectronic devices in solid-state white-light emission, photovoltaic solar cells, and flat panel displays.