Abstract
Defects are capable of modulating various properties of graphene, and thus controlling defects is useful in the development of graphene-based devices. Here we present first-principles calculations, which reveal a new avenue for defect engineering of graphene: the modulation by defects on the highest occupied molecular orbital (HOMO) energy of a charged monolayer graphene quantum dot (GQD) is discriminative. When the charge of a GQD increases its HOMO energy also increases. Importantly, when the GQD contains one particular class of defects its HOMO energy is sometimes higher and sometimes lower than that of the corresponding GQD without any defects, but when the GQD contains another class of defects its HOMO energy is always higher or lower than that of the corresponding intact GQD as its excess charge reaches a critical value. This discriminative modulation could allow defect engineering to control secondary electron ejection in graphene, leading to a new way to develop graphene-based devices.
Highlights
Graphene’s fascinating properties, which include exceptionally high charge carrier mobility,[1,2,3] transparency,[4] thermal conductivity,[5,6] mechanical strength,[7] chemical properties[8] and ultralow secondary electron emission,[9] have led to its intense investigation
With a net charge of 0e to -10e, where e is the elementary charge. These calculations are consistent with the fact that materials undergoing secondary electron emission (SEE) are negatively charged prior to emitting the secondary electrons,[9,31,32,33] and they indicate that the defects modulation of the highest occupied molecular orbital (HOMO) energy of charged graphene quantum dot (GQD) is discriminative and that the defects can be divided into two classes
We investigate the HOMO energies of monolayer graphene containing 88C atoms with different types of defects, including monovacancy, divacancy and Stone-Wales defects, by first-principles calculations
Summary
Graphene’s fascinating properties, which include exceptionally high charge carrier mobility,[1,2,3] transparency,[4] thermal conductivity,[5,6] mechanical strength,[7] chemical properties[8] and ultralow secondary electron emission,[9] have led to its intense investigation. These calculations are consistent with the fact that materials undergoing SEE are negatively charged prior to emitting the secondary electrons,[9,31,32,33] and they indicate that the defects modulation of the HOMO energy of charged GQDs is discriminative and that the defects can be divided into two classes In both classes an increase in extra electrons leads to an increase in the HOMO energy of the GQD, but in one class the HOMO is sometimes higher and sometimes lower than that of the corresponding GQD without any defects, and in the second class the HOMO energy is always higher than that of the corresponding intact GQD after the number of excess electrons reaches a critical value. These results demonstrate that different types of defects can cause different SEE properties in graphene, providing a new pathway to modulate SEE performances of graphene, and to develop new devices based on graphene SEE
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