Efficient gating of epitaxial boron nitride monolayers by substrate functionalization

Abstract

Insulating hexagonal boron nitride monolayers (hBN) are best known for being resistant to chemical functionalization. This property makes hBN an excellent substrate for graphene heterostructures, but limits its application as an active element in nanoelectronics where tunable electronic properties are needed. Moreover, the two-dimensional-materials' community wishes to learn more about the adsorption and intercalation characteristics of alkali metals on hBN, which have direct relevance to several electrochemistry experiments that are envisioned with layered materials. Here we provide results on ionic functionalization of hBN/metal interfaces with K and Li dopants. By combining angle-resolved photoemission spectroscopy (ARPES), x-ray photoelectron spectroscopy, and density functional theory calculations, we show that the metallic substrate readily ionizes the alkali dopants and exposes hBN to large electric fields and band-energy shifts. In particular, if hBN is in between the negatively charged substrate and the positive alkali ion, this allows us to directly study, using ARPES, the effects of large electric fields on the electron energy bands of hBN.

Evolution of electronic structure of few-layer phosphorene from angle-resolved photoemission spectroscopy of black phosphorous

“…It can be seen that lithium doping raises the Fermi level by about 0.4 eV making the conduction band accessible by ARPES and turning BP into a metal. This effect is not common to all semiconductors, e.g., lithium doping does not induce the metallization of the wide band gap material hexagonal boron nitride [48]. In the present case, the doping induced semiconductor-metal transition is eased by the small band gap of BP.…”

Electronic structure of exfoliated and epitaxial hexagonal boron nitride

“…A possible work-around to this problem involves growing single-layer hBN through borazine (B 3 H 6 N 3 ) decomposition on metal surfaces such as Ni(111) [27], Ir(111) [28,29] and Cu(111) [30]. In these cases, hybridization between the hBN π-states and the electronic bands of the underlying metal substrate may significantly influence the bare hBN dispersion, requiring an intercalation step to decouple the hBN from the substrate [31][32][33]. The metal substrates can be avoided altogether by directly growing the hBN on silicon carbide (SiC) followed by annealing above 1150 • C, which produces a G/hBN heterostructure [34].…”

Layered Insulator/Molecule/Metal Heterostructures with Molecular Functionality through Porphyrin Intercalation

“…A promising approach for the fabrication of materials with tailored physical and chemical properties is to synthesize hybrid materials by combining different material classes such as two-dimensional (2D) layers and organic molecular materials at the nanoscale. − h -BN is one of the prominent building blocks for such architectures due to its insulating behavior, high thermal conductivity, and chemical and thermal stability. ,− Intercalation of atoms and small molecules has been studied for h- BN monolayers , and other 2D materials like graphene, , as well as for multilayer materials, , as a way to modify the materials’ properties and to fabricate heterostructures that are not accessible via conventional delamination and transfer processes of 2D materials. − Furthermore, reactions of small intercalated molecules, e.g. , CO and ethylene, have been reported. − To date, only very few studies have addressed imaging intercalated molecular entities such as C 60 underneath graphene. ,, However, none of these reports investigated the intercalation of functional molecules and its impact on the intrinsic properties of intercalated molecules.…”

“…1−3 h-BN is one of the prominent building blocks for such architectures due to its insulating behavior, high thermal conductivity, and chemical and thermal stability. 1,4−6 Intercalation of atoms and small molecules has been studied for h-BN monolayers 7,8 and other 2D materials like graphene, 9,10 as well as for multilayer materials, 11,12 as a way to modify the materials' properties and to fabricate heterostructures that are not accessible via conventional delamination and transfer processes of 2D materials. 13−20 Furthermore, reactions of small intercalated molecules, e.g., CO and ethylene, have been reported.…”