The synthesis of boron-, carbon-, and nitrogen-containing 2D materials on Ir(111): the role of boron carbide

The preparation of mixed boron-, carbon-, and nitrogen-containing 2D materials has been intensively studied to optimize their electronic properties.For this purpose, the decomposition of bis-BN cyclohexane (B 2 N 2 C 2 H 12 ) was studied in this work on Ir(111) using electron diffraction as well as core and valence band photoemission.The underlying energetics has been disclosed by density functional theory calculations.The expectation that a precursor with all three elements in its ring would facilitate the formation of atomically mixed BCN films was not met.When the molecules were adsorbed at 50 • C, followed by subsequent annealing, the rupture of the sixmembered rings started already at 275 • C. The preparation of the overlayer in the range of 650 • C -740 • C primarily resulted in the formation of phase-separated h-BN and graphene domains.However, increasing the preparation temperature to 980 • C -1110 • C considerably enhanced mixing.At the obtained N-deficient average compositions: (i) the average size of h-BN islands decreased much, down to ~1 nm or below, and they were mostly terminated by B atoms; (ii) the area covered by extended h-BN domains decreased and disappeared; (iii) surplus B atoms were alloyed into graphene forming a 2D boron carbide matrix in which h-BN nanodomains are embedded; (iv) the edge region of h-BN nanoislands can be considered chemically a one-dimensional mixed BCN phase.Our results revealed that the presence of boron carbides should also be considered when studying BCN layers.For the first time, we experimentally characterized their band structure by momentum microscopy.