Abstract
Stanene, a two-dimensional topological insulator composed of Sn atoms in a hexagonal lattice, is a promising contender to Si in nanoelectronics. Currently it is still a significant challenge to achieve large-area, high-quality monolayer stanene. We explore the potential of Ag(111) surface as an ideal substrate for the epitaxial growth of monolayer stanene. Using first-principles calculations, we study the stability of the structure of stanene in different epitaxial relations with respect to Ag(111) surface, and also the diffusion behavior of Sn adatom on Ag(111) surface. Our study reveals that: (1) the hexagonal structure of stanene monolayer is well reserved on Ag(111) surface; (2) the height of epitaxial stanene monolayer is comparable to the step height of the substrate, enabling the growth to cross the surface step and achieve a large-area stanene; (3) the perfect lattice structure of free-standing stanene can be achieved once the epitaxial stanene monolayer is detached from Ag(111) surface; and finally (4) the diffusion barrier of Sn adatom on Ag(111) surface is found to be only 0.041 eV, allowing the epitaxial growth of stanene monolayer even at low temperatures. Our above revelations strongly suggest that Ag(111) surface is an ideal candidate for growing large-area, high-quality monolayer stanene.
Highlights
Quantum spin Hall (QSH) insulators are new states of condensed matter, in which insulating bulk and metallic edge states coexist[1,2]
Monolayer and few-layer stanene were successfully grown epitaxially on Bi2Te3 (111) surface via molecular beam epitaxy (MBE) and the obtained atomic structures and their electronic properties were studied by using scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations[28]
We need to answer the following questions: What is the nature of the interaction between stanene epilayer and Ag(111) surface? What is the resulting epilayer structure of stanene upon such interaction? If the epilayer is detached by etching away Ag substrate, can the epilayer fully recover to the free-standing lattice structure of monolayer stanene? Clearly, answers to these questions are of scientific interest, and of significant consequence on whether Ag(111) is suitable for the epitaxial growth of large-area, high-quality stanene monolayer
Summary
Quantum spin Hall (QSH) insulators are new states of condensed matter, in which insulating bulk and metallic edge states coexist[1,2]. It is worth noting that surface halogenation is able to further enlarge the bang gap of stanene to more than 300 meV16,17,19 Such a large band gap instigated by SOC effect is sufficient for application as a room-temperature QSH insulator. Monolayer and few-layer stanene were successfully grown epitaxially on Bi2Te3 (111) surface via MBE and the obtained atomic structures and their electronic properties were studied by using scanning tunneling microscopy (STM), angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations[28]. Previous studies clearly showed that Ag(111) surface is such an ideal substrate for the epitaxial growth of silicene[29,30,31,32,33,34,35,36,37] It is still an open question whether monolayer stanene can be grown on Ag(111) surface. Our studies here provide compelling evidences that Ag(111) surface is an ideal candidate for growing monolayer stanene
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