Abstract
The experimental realization of two-dimensional materials such as graphene, silicene and germanene has attracted incredible interest ranging from understanding their physical properties to device applications. During the fabrication and processing of these two-dimensional materials, structural defects such as vacancies may be produced. In this work we have systemically investigated the formation energies, electronic and magnetic properties of graphene, silicene and germanene with vacancies in the framework of spin polarized density functional theory. It is found that the magnetic moment of graphene and silicene with vacancies decreases with the increase in the concentration of vacancies. However, germanene remains non-magnetic irrespective of the vacancy concentration. Low-buckled silicene and germanene with vacancies may possess remarkable band gaps, in contrast to planar graphene with vacancies. With the formation of vacancies silicene and germanene demonstrate a transition from semimetal to semiconductor, while graphene turns to be metallic.
Highlights
It has been shown that vacancy-induced magnetism in silicene should be studied with generalized gradient approximation (GGA) rather than local density approximation (LDA) since LDA underestimates the vacancy-induced magnetism to a large extent.[41]
Li et al studied the stability of silicene with vacancy clusters, extended line defects and di-adatoms in the framework of density functional theory (DFT) and ab-initio molecular dynamic (AIMD) simulations
We find that silicene with vacancies becomes a FM semiconductor at the vacancy concentration of 2%
Summary
The successful fabrication of two-dimensional graphene, silicene and germanene has attracted great attention because of their potential for applications in various fields such as electronics, photonics, spintronics and sensing.[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19] The striking similarity among graphene, silicene and germanene arises from the fact that carbon, silicon and germanium belong to the same group in the periodic table of elements. It has been shown that vacancy-induced magnetism in silicene should be studied with generalized gradient approximation (GGA) rather than local density approximation (LDA) since LDA underestimates the vacancy-induced magnetism to a large extent.[41] Li et al studied the stability of silicene with vacancy clusters, extended line defects and di-adatoms in the framework of density functional theory (DFT) and ab-initio molecular dynamic (AIMD) simulations. They found that the small defects have the coalesce tendency to form highly stable vacancy clusters. Silicene and germanene with vacancies may possess remarkable band gaps, in contrast to graphene with vacancies
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