Experimental evidence of surface copper boride

To validate the crystal structure and elucidate the formation mechanism of the unexpected surface copper boride,a systematic scanning tunneling microscope,X-ray photoelectron spectroscopy,angle-resolved photoemission spectroscopy,and aberrationcorrected scanning transmission electron microscopy investigations were conducted to confirm the structure of copper-rich boride Cu_(8)B_(14)after depositing boron on single-crystal Cu(111)surface under ultrahigh vacuum.First-principles calculations with defective surface models further indicate that boron atoms tend to react with Cu atoms near terrace edges or defects,which in turn shapes the intermediate structures of copper boride and leads to the formation of stable Cu-B monolayer via large-scale surface reconstruction eventually.

Formation of copper boride on Cu(111)

Boron forms compounds with nearly all metals,with notable exception of copper and other group IB and IIB elements.Here,we report an unexpected discovery of ordered copper boride grown epitaxially on Cu(111)under ultrahigh vacuum.Scanning tunneling microscopy experiments combined with ab initio evolutionary structure prediction reveal a remarkably complex structure of 2D-Cu_(8)B_(14).Strong intra-layer p–d hybridization and a large amount of charge transfer between Cu and B atoms are the key factors for the emergence of copper boride.This makes the discovered material unique and opens up the possibility of synthesizing ordered low-dimensional structures in similar immiscible systems.