Electronic and transport properties of structural defects in monolayer germanene: An ab initio investigation

• Structural, STM, electronic and transport properties of germanene with structural defects.
• Point defects Stone-Wales, single vacancy, divacancy-5-8-5 and 555-777.
• Stone-Wales defect has the lowest formation energy and none of the defects presents magnetism.
• The defects, create scattering states near the Fermi level, diminishing the current in the system.

Ab initio electronic structure and transport calculations of 2D hexagonal germanium with four possible structural defects were performed. The considered defects were Stone–Wales (SW), single vacancy (5–9) and two divacancies (5–8–5 and 555–777). We showed that these defects present a local reconstruction that can be clearly identified by STM images. Among the investigated defects, we verified that the SW defect has the lowest formation energy. We showed that in the presence of structural defects the 2D hexagonal germanium maintains its Dirac cone feature only for the single vacancy. The divacancies and the SW defect destroy the linear dispersion relation of the electrons, near the Fermi level, in this system. Moreover, we verified that these defects create scattering centers, which can lead to diminishing of the current by roughly 42% for the Stone–Wales and single vacancy, 55% for the divacancy 5–8–5 and 68% for the 555–777 divacancy.