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Modifying the geometric and electronic structure of hexagonal boron nitride on Ir(111) by Cs adsorption and intercalation

DOI: 10.1103/PhysRevB.98.195443 DOI Help

Authors: Jiaqi Cai (Westfälische Wilhelms-Universität Münster; Universität zu Köln; Universität Siegen) , Wouter Jolie (Universität zu Köln) , Caio C. Silva (Westfälische Wilhelms-Universität Münster; Universität zu Köln) , Marin Petrović (Center of Excellence for Advanced Materials and Sensing Devices, Institute of Physics, Croatia) , Christoph Schlueter (Diamond Light Source) , Thomas Michely (Universität zu Köln) , Marko Kralj (Center of Excellence for Advanced Materials and Sensing Devices, Institute of Physics, Croatia) , Tien-lin Lee (Diamond Light Source) , Carsten Busse (Westfälische Wilhelms-Universität Münster; Universität zu Köln; Universität Siegen)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 98

State: Published (Approved)
Published: November 2018
Diamond Proposal Number(s): 12558

Abstract: Epitaxial hexagonal boron nitride on Ir(111) is significantly modified by adsorption and intercalation of alkali-metal atoms. Regarding geometry, intercalation lifts the two-dimensional layer from its substrate and reduces the characteristic corrugation imprinted by direct contact with the metal substrate. Moreover, the presence of charged species in close proximity to the hexagonal boron nitride (hBN) layer strongly shifts the electronic structure (valence bands and core levels). We used scanning tunneling microscopy, low-energy electron diffraction, x-ray photoelectron spectroscopy (XPS), and the x-ray standing wave technique to study changes in the atomic structure induced by Cs adsorption and intercalation. Depending on the preparation, the alkali-metal atoms can be found on top and underneath the hexagonal boron nitride in ordered and disordered arrangements. Adsorbed Cs does not change the morphology of hBN/Ir(111) significantly, whereas an intercalated layer of Cs decouples the two-dimensional sheet and irons out its corrugation. XPS and angle-resolved photoelectron spectroscopy reveal a shift of the electronic states to higher binding energies, which increases with increasing density of the adsorbed and intercalated Cs. In the densest phase, Cs both intercalates and adsorbs on hBN and shifts the electronic states of hexagonal boron nitride by 3.56 eV. As this shift is not sufficient to move the conduction band below the Fermi energy, the electronic band gap must be larger than 5.85 eV.

Journal Keywords: Electronic structure; Surface & interfacial phenomena; Surface adsorption; 2-dimensional systems; Angle-resolved photoemission spectroscopy; Scanning tunneling microscopy; X-ray standing waves

Subject Areas: Materials, Physics

Instruments: I09-Surface and Interface Structural Analysis