Large-area borophene sheets on sacrificial Cu(111) films promoted by recrystallization from subsurface boron

Abstract

Borophene, an atomically thin covalently bonded boron sheet, has attracted great attention as a novel quantum material because of its structural tunability and potential utilization in flexible and transparent electronics. So far, borophene has been synthesized on silver or copper single crystals, but these substrates are small, very expensive, and unsuitable for study of transport properties or electronics applications. Here, we report synthesis of borophene on nanometer-scale thick Cu(111) films grown on sapphire. We have developed a process of enlarging faceted borophene islands, by repeated submersion of boron into copper at high temperature and resurfacing and re-crystallization at lower temperature. This discovery was enabled by real-time feedback from low-energy electron microscopy and diffraction. We demonstrate synthesis of borophene as faceted micrometer-size monocrystal islands or as full-monolayer sheets. The process is scalable to wafer size; moreover, Cu films could be sacrificed and sapphire reused. Our work opens the door for new experiments and brings applications one step closer.npj Quantum Materials (2019) 4:40 ; https://doi.

Borophenes made easy

“…This demonstrates the substantial decrease of the growth kinetics after the completion of the first atomic layer and strongly suggests that the molecular precursor undergoes dehydrogenation reactions assisted by the catalytic surface, yielding intermediate boron species that form large single-crystalline domains. Boron subsurface diffusion and segregation mechanisms may not generally be excluded but are not expected to dominate the growth at the applied conditions due to the kinetic differences between on surface film formation and bulk diffusion mechanisms ( 16 , 26 , 37 ). Low-energy electron diffraction (LEED) imaging reveals successful borophene formation at temperatures as low as 1073 K (fig.…”

Borophene: New Sensation in Flatland

“…Wu et al. [ 26 ] have proposed a modified considerably improved technique for a CVD growth of monolayer borophene sheets having micrometer sizes on thick Cu(111) films grown on sapphire. This further advances the borophene‐based devices and paves the way for the realization of corresponding electronic devices.…”

Borophene via Micromechanical Exfoliation

“…Experimental realization of borophene has earlier been reported by atomic layer deposition (ALD), [17] molecular beam epitaxy (MBE), [18] and chemical vapor deposition [19,20] over a silver surface. The irony was that the crystal structure of silver substrate was held responsible for the very crystallization of borophene.…”