Segregation-Enhanced Epitaxy of Borophene on Ir(111) by Thermal Decomposition of Borazine

Abstract

Like other 2D materials, the boron-based borophene exhibits interesting structural and electronic properties. While borophene is typically prepared by molecular beam epitaxy, we report here on an alternative way of synthesizing large single-phase borophene domains by segregation-enhanced epitaxy. X-ray photoelectron spectroscopy shows that borazine dosing at 1100 °C onto Ir(111) yields a boron-rich surface without traces of nitrogen. At high temperatures, the borazine thermally decomposes, nitrogen desorbs, and boron diffuses into the substrate. Using time-of-flight secondary ion mass spectrometry, we show that during cooldown the subsurface boron segregates back to the surface where it forms borophene. In this case, electron diffraction reveals a (6 × 2) reconstructed borophene χ6-polymorph, and scanning tunneling spectroscopy suggests a Dirac-like behavior. Studying the kinetics of borophene formation in low energy electron microscopy shows that surface steps are bunched during the borophene formation, resulting in elongated and extended borophene domains with exceptional structural order.

Exploring the emerging applications of the advanced 2-dimensional material borophene with its unique properties

“…15(eand f) , where the decrement in the Fermi level to form a V-shape is partial evidence for borophene on Ir(111) showing the Dirac-like behavior. 99 The presumed electronic band structures of χ 4 -5H-borophene indicated in Fig. 15(g and h) , disclosed its metallic behavior based on the Density Functional Theory (DFT) through the Vienna ab initio Simulation Pack (VASP), 121 where the metallic behavior is significantly contributed by the p-orbitals, which is comparable to previous reports 122 indicating χ 4 -5H-borophene to be suitable for employment in the applications of memory devices as well.…”

“…Further, on increasing the B concentration, the initially trigonal Au(111) network breaks, resulting in a large-scale borophene island and can extend to several nanometres on increasing the boron dose via electron-beam evaporation. 95 Although MBE is a typical process for preparing substrate-supported borophene with high uniformity and fewer defects, an alternate method similar to MBE for borophene synthesis over mica 98 and Ir(111) 99 was reported via van der Waals epitaxial growth and segregation-enhanced epitaxial growth (schematically shown in Fig. 10(f) ), respectively, which resulted in larger single-phased borophene.…”

Borophenes made easy

“…This will open a vast variety of approaches to study fundamental aspects of these synthetic 2D materials and finally bring their incorporation in technologically relevant applications into reach. Note added: During evaluation of this manuscript, a study reporting another approach to borophene synthesis on Ir(111) was published ( 51 ).…”

Macroscopic Single-Phase Monolayer Borophene on Arbitrary Substrates

“…11,[14][15][16] For example, full monolayer Bo coverage has been reached on Ag(111), 17 Cu(111), 9 Cu(100) 18 and Ir(111). 13,19 Moreover, the monolayer limit has been surpassed by the synthesis of a full Bo bilayer on Ru(0001) 20 and Cu(111). 21 In all these cases, Bo samples were restricted in size only by the size of their substrates.…”