Controllable bandgaps of multilayer graphene quantum dots tuned by stacking thickness, interlayer twist and external electric field.

Recent advances in the precise preparation, process, and manipulation of multilayer graphene quantum dots make it possible to engineer effectively their energy gaps (Δε) by tuning the stacking thickness, interlayer twist angle, quantum dot size, and external electric field strength. The coupling mechanism among these operations is however ambiguous. Using first-principles calculations, the Δε variations of multilayer graphene quantum dots are studied at a varying stacking thickness, twist angle, and field strength. The combination of these diverse operations not only widens the Δε windows but also generates quasi-continuous Δε variations. Every operation may alter the interlayer coupling strength, which becomes more sensitive under the combination of two or more operations, resulting from the different responses of the Kohn–Sham orbitals around the Fermi level against the operations. Analysis of the vertical polarizability reveals that interlayer charge transfer ability is tuned by the operations, which accounts for the variations in interlayer coupling and consequently in Δε. Understanding the coupling mechanism is helpful for the precise control over the band gaps of the multilayer graphene quantum dots in their optoelectronic applications. [ABSTRACT FROM AUTHOR]