Vacancy induced robust magnetism in graphene hexagonal-boron nitride in-plane hybrids with hexagonal shaped islands

Abstract

We present the results of density functional theory (DFT) calculations on the vacancy-defected graphene-hBN (GBN) nanosheet embracing a hexagonal island. Hexagonal shaped h-BN and G islands of varying sizes are respectively patterned in G and h-BN nanosheets for possible uses of GBN hybrid in device applications. Three different types of mono vacancies were formed at various sites of GBN hybrid. Two distinct C mono vacancies, B and N mono vacancy were formed at G/h-BN interface. We additionally formed C mono vacancy in G region, and B and N mono vacancies in h-BN region of the hybrid nanosheet. Possible effects of vacancies and size effects of island on the electronic and magnetic properties of hybrid were examined in great detail. Calculated vacancy formation energies show that N vacancy exhibits lower formation energy than B one. Besides, the interface is the energetically most favorable place, regardless of the type of vacancy. All pristine hybrids with hexagonal islands are non-magnetic semiconductors. However, depending on the type of vacancy and vacancy site, the GBN hybrid can become magnetic with a considerable amount of magnetic moment. Because of the high magnetization energy, the magnetic order is considered to be robust against thermal excitations at finite temperatures. Our results indicated that defective hybrids with G islands have greater potential for magnetic applications. Mono vacancies introduce flat (dispersionless) states near the Fermi level, and these flat energy states lead to localized, integer-valued magnetic moment. In general, no correlation was observed between the island size and the magnetic moment of a defective hybrid. Nevertheless, in the case of C (B) vacancy in G (h-BN) layout, the magnetic moment increases with increasing island size. This result could point to a possible coupling between the defect and hexagonal island.