Electronic structures and transport properties of cove-edged graphene nanoribbons

In this comprehensive study, we undertake a thorough theoretical examination of the electronic subband structures within cove-edged zigzag graphene nanoribbons (CZGNRs) using the tight-binding model. These unique nanostructures arise from the systematic removal of carbon atoms along the zigzag edges of conventional zigzag graphene nanoribbons (ZGNRs). Notably, CZGNRs that exhibit intriguing band gaps can be conceptualized as interconnected graphene quantum dots (GQDs). An essential finding of our investigation is the inverse relationship between the size of GQDs and the band gaps of CZGNRs, a relationship that remains consistent regardless of the number of GQDs present. Additionally, we delve into the examination of electron effective masses in proximity to the edges of the first conduction subband of CZGNRs as GQD sizes expand. We observe a significant increase in electron effective masses as GQDs become larger, which is attributed to the increasing similarity between larger GQDs and ZGNRs. To further understand the practical implications, we explore the transport properties of finite CZGNRs when connected to electrodes through line contacts. The presence of edge defects introduces intriguing asymmetries in the tunneling current, leading to a significant reduction in its magnitude. Notably, we observe that the saturation current magnitude is less influenced by the length of CZGNRs and is instead more sensitive to the choice of materials used for the contacted electrodes. Lastly, we investigate the tunneling currents through GQDs featuring boron nitride textures within the Coulomb blockade region, unveiling an irregular staircase-like pattern in the tunneling current behavior.
Comment: 10 pages and 11 figures