Processes at Surfaces

Coating metals with a high-quality monolayer of insulator hexagonal boron nitride can protect them from corrosion. However coating the metal with a multi-layered but cracked film can even increase corrosion. We have shown that defects in hexagonal boron nitride deposited on Cu surface act as an active site for water dissociation into hydrogen and oxygen. The interactions between atomic oxygen and B atoms lead to accumulation of O atoms between boron nitride film and Cu, which accelerates the formation of Cu oxide/hydroxide.

Figure a) Energy diagram for H₂O dissociation on Cu(111) surface (black line), on BNNF/Cu(111) (red line), between the BNNF and Cu(111) (blue line), and along the edges of OH-terminated BNNF (green line). Optimized configurations of b) H₂O*, c) H*, d) OH*, and e) O* adsorbed in the vicinity of an OH-terminated zigzag edge of BNNF on a Cu(111) surface. B: blue; N: grey; O: red; H: electric blue (small spheres); Cu: celeste (large spheres).

Bottom-up strategies can be effectively implemented for the fabrication of atomically precise graphene nanoribbons. Using 10,10′-dibromo-9,9′-bianthracene (DBBA) as a molecular precursor to grow nanoribbons we compare the on-surface reaction pathways for DBBA molecules on Cu(111) and Cu(110). Experimental and theoretical results reveal a significant increase in reactivity for the open and anisotropic Cu(110) surface in comparison with the close-packed Cu(111). This increased reactivity results in a predominance of the molecular–substrate interaction over the intermolecular one, which has a critical impact on the transformations of DBBA on Cu(110). We have demonstrated that nanographene units coordinated with bromine adatoms are able to arrange in highly regular arrays potentially suitable for nanotemplating.

Figure Formation of graphene nanoribbons on metal surfaces.

A novel single-phase structure of borophene (two-dimensional layer of boron atoms) on Ir(111) surface has been discovered via a combination of the large-scale computer simulations and experiments. The exact atomic arrangement of this complex borophene phase has been reviealed and its structure is found to be different from all known B polymorphs. It should be noted that borophene has been at the cutting edge of contemporary research in the last few years for its outstanding properties, somewhat similar to those of graphene. Discovered experimentally in 2015, it was mainly (with a few exceptions) studied on Ag(111), where it can be formed as a mixture of several different phases. As the physical properties of these phases are intrinsically different, their co-existing hindered the practical implementation of this material. Therefore our discovery of stable single-phase borophene on Ir(111) is a major step towards unleashing the borophene’s potential.

Figure (a) Optimized structure of borophene on Ir(111), (b) DFT simulated STM of borophene on Ir(111) (left); a cut from raw experimental data (right). In the center, a proposed atomic arrangement from (a) is overlaid. (c) Calculated charge redistribution density.

Relevant publications

• • N. A. Vinogradov, A. Lyalin, T. Taketsugu, A. S. Vinogradov, and A. Preobrajenski, Single-Phase Borophene on Ir(111): Formation, Structure and Decoupling from the Support, ACS Nano 13, 14511-14518 (2019).

  • K. A. Simonov, A. V. Generalov, A. S. Vinogradov, G. I. Svirskiy, A. A. Cafolla, C. McGuinness, T. Taketsugu, A. Lyalin, N. Mårtensson, and A. B. Preobrajenski, Synthesis of armchair graphene nanoribbons from the 10,10’-dibromo-9,9’-bianthracene molecules on Ag(111): the role of organometallic intermediates, Sci. Rep. 8, 3506 (2018).

  • M. H. Khan, S. S. Jamali, A. Lyalin, P. J. Molino, L. Jiang, H. K. Liu, T. Taketsugu, and Z. Huang, Atomically Thin Hexagonal Boron Nitride Nanofilm for Cu Protection: The Importance of Film Perfection, Adv. Mater. 29, 1603937 (2017). (Highlighted by Nature, 540, 11, 2016).

  • K.A. Simonov, N.A. Vinogradov, A.S. Vinogradov, A.V. Generalov, E.M. Zagrebina, G.I. Svirskiy, A.A. Cafolla, T. Carpy, J.P. Cunniffe, T. Taketsugu, A. Lyalin, N. Mårtensson, and A.B. Preobrajenski, From graphene nanoribbons on Cu (111) to nanographene on Cu (110): Critical role of substrate structure in the bottom-up fabrication strategy, ACS Nano 9, 8997-9011 (2015).