Photoluminescence Enhancement Exceeding 10-Fold from Graphene via an Additional Layer: Photoluminescence from Monolayer and Bilayer Graphene Epitaxially Grown on SiC

Abstract

Graphene exhibits characteristic optical properties and has garnered significant attention for application in light-emitting devices. Bilayer graphene is expected to be more suitable than monolayer graphene for application because of its strong luminescence owing to weak substrate effects. To further investigate this, we analyze the femtosecond photoluminescence (PL) decay and time-resolved PL spectra of epitaxial monolayer and bilayer graphene on SiC. The bilayer graphene emits longer and more than 10-fold stronger PL compared with the monolayer graphene. The PL decay curves and spectra are analyzed using a three-temperature model. The time evolutions of the carrier temperature and coupling coefficients between the carriers of graphene and each of the phonons of graphene and the substrate are obtained. The carrier temperature in bilayer graphene after femtosecond laser pulse excitation is approximately 120 K higher than that in monolayer graphene under our experimental conditions, thereby explaining the longer and stronger PL from the bilayer graphene. This study demonstrates the superior ability of bilayer graphene as a light-emitting material compared with monolayer graphene and promotes research pertaining to graphene-based light-emitting devices.