Tuning the Electronic and Transport Properties of Penta-Graphene Nanoribbons by Creating Vacancies and Applying an External Electric Field

Abstract

Introducing defect vacancies into nanostructures is a straightforward yet powerful technique employed by scientists to manipulate their properties. In this study, we used a tight-binding model to investigate the effects of an external electric field and the creation of double vacancies at different sites on penta-graphene nanoribbons on the electronic and transport properties. Understanding the effects of external electric fields and vacancy creation on the electronic and transport properties of penta-graphene nanoribbons is important for the advancement of nanoelectronics and the development of innovative applications. After calculating the formation energy for all vacancy structures, it was determined that the maximum stability is achieved when the second vacancy is at the C₂ site. By creating vacancies in the structure, in addition to tuning the energy gap, an indirect–to–direct bandgap transition can be achieved in penta-graphene nanoribbons. The presence of a direct gap in the electronic properties of penta-graphene nanoribbons has significant implications. Direct bandgap materials can absorb and emit photons with energies close to the bandgap energy and may be better suited for optical devices. It was also observed that the creation of vacancies in penta-graphene nanoribbons leads to a phase transition from a semiconductor to a metal. Next, the effect of these vacancies on the transport properties of penta-graphene nanoribbons was investigated. The results clearly show that the maximum current and threshold voltage can be controlled by creating vacancies at various sites on the nanoribbon. In general, by creating double vacancies in the structure or applying an external electric field, an indirect transition to a direct band gap and a semiconductor–to–metal phase transition have been observed. Additionally, when a double vacancy is introduced into the system and an external electric field is applied simultaneously, flat bands are observed in the band structure, as are the tunable band gap, semiconductor–to–metal phase transition, and indirect–to–direct bandgap transition. Additionally, to explore the cause of the change in electronic and transport properties with the creation of a vacancy in the structure, the charge density distribution of carbon atoms was analyzed using density functional theory calculations. Due to the difference in charge density between the penta-graphene nanoribbon sites, significant charge transfer occurs in the structure after a double vacancy is created in the structure. This charge transfer leads to the generation of an electric current in the nanoribbon. Because of these unique characteristics, penta-graphene nanoribbons are promising candidates for the development of solar cells.