Quantum confinement in graphene quantum dots

Abstract

By performing density functional theory calculations, we studied the quantum confinement in charged graphene quantum dots (GQDs), which is found to be clearly edge and shape dependent. It is found that the excess charges have a large distribution at the edges of the GQD. The resulting energy spectrum shift is very nonuniform and hence the Coulomb diamonds in the charge stability diagram vary irregularly, in good agreement with the observed nonperiodic Coulomb blockade oscillation. We also illustrate that the level statistics of the GQDs can be described by a Gaussian distribution, as predicted for chaotic Dirac billiards. The charge stability diagram (left) and the Gaussian distribution of the width of the Coulomb diamonds (right), indicating the nonperiodic Coulomb blockade oscillation in GQD due to quantum confinement. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Unravelling the Potential of Graphene Quantum Dots in Biomedicine and Neuroscience

“…GQDs are small graphene flakes (<100 nm) in which the quantum confinement of excitons becomes dominant [21], causing a random spacing of Coulomb blockade peaks rather than a periodic distribution [6]. Interestingly, in GQDs, quantum confinement is not given only by the size, since different boundaries lead to diverse spin polarization and energy spectrum (Figure 2A).…”

“…Interestingly, in GQDs, quantum confinement is not given only by the size, since different boundaries lead to diverse spin polarization and energy spectrum (Figure 2A). Indeed, other factors involved in quantum confinement are related to the chirality and shape of graphene edges [6,29], thus it strictly depends on GQDs' synthesis method.…”

“…Quantum dots are semiconducting nanomaterials with dimensions below 100 nm [5]. Physical and chemical properties of QDs strictly depend on their size, due to quantum confinement effect [6]. Briefly, when an electron is promoted to the conduction band from the valence band, it leaves an empty electron state, a "hole".…”

Quantized Electron Transport Through Graphene Nanoconstrictions

“…GNRs behave as singlechannel room-temperature ballistic electrical conductors on a length scale greater than ten microns [23]. Therefore, they are good candidates to exploit quantum effects such as the Fano effect [24,25,26,27,28,29], resonant tunneling [30,31,32] and quantum size effects [33,34], even at room temperature. GNRs are commonly referred to as graphene nanoconstrictions (GNCs) or quantum point contacts when their length is close to their width.…”

Suppression of localized transmission peaks and deviation from Matthiessen's rule in disordered armchair graphene nano-ribbons due to acoustic phonons

“…In disordered GNRs, the transport of carriers in the localization regime is due to coherent scattering where the localized states form over the total length of the ribbons [16]. In the case of graphene quantum dots [17] or graphene granular systems [18], the transport of carriers is similar to the granular metals [19] [20]. In such materials the transport of carriers is due to co-tunneling or sequential tunneling depending on the temperature or applied electric field.…”