Covalent organic frameworks (COFs) are molecule-based 2D and 3D materials that possess a wide range of mechanical and electronic properties. We have performed a joint experimental and theoretical study of the electronic structure of boroxine-linked COFs grown under ultrahigh vacuum conditions and characterized using scanning tunneling spectroscopy on Au(111) and hBN/Cu(111) substrates. Our results show that a single hBN layer electronically decouples the COF from the metallic substrate, thus suppressing substrate-induced broadening and revealing new features in the COF electronic local density of states (LDOS). The resulting sharpening of LDOS features allows us to experimentally determine the COF band gap, bandwidths, and the electronic hopping amplitude between adjacent COF bridge sites. These experimental parameters are consistent with the results of first-principles theoretical predictions.
|Original language||English (US)|
|State||Published - Jan 15 2020|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This research was supported by the Army Research Office Multidisciplinary University Research Initiative (MURI) program under Grant No. W911NF-15-1-0447 (STM spectroscopy, DFT analysis) and by the U.S. Department of Energy, Office of Basic Energy Sciences Nanomachine
Program, under Contract No. DEAC02-05CH11231 (sample preparation). The work at Georgia Tech was supported in part by a grant of computer time from the DOD High Performance Computing Modernization Program.