Epitaxial hexagonal boron nitride on Ir(111): A work function template

Abstract

Hexagonal boron nitride (h-BN) is a prominent member in the growing family of two-dimensional materials with potential applications ranging from being an atomically smooth support for other two-dimensional materials to templating growth of molecular layers. We have studied the structure of monolayer h-BN grown by chemical vapor deposition on Ir(111) by low-temperature scanning tunneling microscopy (STM) and spectroscopy (STS) experiments and state-of-the-art density functional theory (DFT) calculations. The lattice mismatch between the h-BN and Ir (111) surface results in the formation of a moiré superstructure with a periodicity of ∼29Å and a corrugation of ∼0.4Å. By measuring the field emission resonances above the h-BN layer, we find a modulation of the work function within the moiré unit cell of ∼0.5 eV. DFT simulations for a 13-on-12 h-BN/Ir(111) unit cell confirm our experimental findings and allow us to relate the change in the work function to the subtle changes in the interaction between boron and nitrogen atoms and the underlying substrate atoms within the moiré unit cell. Hexagonal boron nitride on Ir(111) combines weak topographic corrugation with a strong work function modulation over the moiré unit cell. This makes h-BN/Ir(111) a potential substrate for electronically modulated thin film and heterosandwich structures.

Striped, honeycomb, and twisted moiré patterns in surface adsorption systems with highly degenerate commensurate ground states

“…Understanding and predicting these states and the transition between them has been of great fundamental interest for many years. Most recently there has been considerable work devoted to the study of the growth and properties of two-dimensional (2D) films, in particular graphene [1][2][3][4][5][6][7][8][9][10][11], and other films of honeycomb symmetry such as so-called hexagonal boron nitride or hBN (which actually forms a honeycomb structure) [12][13][14][15][16][17][18][19] and MoS 2 [20][21][22]. These systems typically show 2D moiré patterns that are defined by a triangular (honeycomb) array of commensurate regions when grown on a substrate with an adsorption surface potential having a triangular (honeycomb) array of minima.…”

Annealing of ion-irradiated hexagonal boron nitride on Ir(111)

“…1(a) depicts an apparent corrugation of at most 0.5Å. For the insulator h-BN, the STM contrast and corrugation vary strongly with the tunneling parameters, e.g., the valleys may even appear as protrusions [25,63].…”

“…Besides exfoliation, chemical vapor deposition on catalytically active metals is a way to prepare well-defined monolayers [13]. Examples are epitaxial h-BN layers on Rh(111) [14][15][16], Ru(0001) [17][18][19], Pt(111) [20], and Ir(111) [21][22][23][24][25][26][27].…”

Chemical Vapour Deposition of sp2 Hybridised Boron Nitride

“…Due to the catalytic activity of the surfaces of these metals reduction of the growth temperature is possible. Metals commonly employed for the deposition of sp 2 -BN are Cr, Fe, Ni, Cu, Ru, Rh, Pd, Ir, Pt [93,94,95,96,97,98]. As already mentioned due to the low growth temperature thickness of the ordered sp 2 -BN is limited to a few basal planes, usually not more than 10 [99].…”