Synthesis of Borophane Polymorphs via Hydrogenation of Borophene

Borophene refers to the family of synthetic two-dimensional polymorphs of boron, which has attracted significant attention due to anisotropic metallicity, correlated electron phenomena, and diverse superlattice structures. While borophene heterostructures have recently been realized, ordered chemical modification of borophene has not yet been reported. Here, we synthesize ‘borophane’ polymorphs by hydrogenating borophene with atomic hydrogen in ultrahigh vacuum [1]. Through atomic-scale imaging, spectroscopy, and first principles calculations, the most prevalent borophane polymorph is shown to possess a combination of two-center-two-electron boron-hydrogen and three-center-two-electron boron-hydrogen-boron bonds. Borophane polymorphs are metallic with modified local work functions, and can be reversibly returned to pristine borophene via thermal desorption of hydrogen. Hydrogenation also provides chemical passivation as borophane is shown to suppress oxidation for multiple days following ambient exposure.<br/><b>Acknowledgement:</b><br/>This work was supported by the Office of Naval Research (ONR N00014-17-1-2993) and the National Science Foundation Materials Research Science and Engineering Center (NSF DMR-1720139).<br/><b>References:</b><br/>[1] Qiucheng Li, Venkata Surya Chaitanya Kolluru, Matthew S. Rahn, Eric Schwenker, Shaowei Li, Richard G. Hennig, Pierre Darancet, Maria K. Y. Chan, Mark C. Hersam. Synthesis of borophane polymorphs through hydrogenation of borophene. <b><i>Science</i></b>,<b> 2021</b>, <i>371</i> (6534), 1143<i>.</i>