[paper] Boropheneand Metal Interface

Vaishnavi Vishnubhotla, Sanchali Mitra, and Santanu Mahapatraa

First-principles based study of 8-Pmmn boropheneand metal interface

J. Appl. Phys. 134, 034301 (2023); doi: 10.1063/5.0144328

DOI 10.1063/5.0144328

Nano-Scale Device Research Laboratory, Department of Electronic Systems Engineering, 

Indian Institute of Science (IISc) Bangalore, India

Abstract: Borophene, the lightest member of mono-elemental 2D materials family, has attracted much attention due to its intriguing polymorphism. Among many polymorphs, digitally discovered 8-Pmmn stands out owing to its unique tilted-Dirac fermions. However, the property of interfaces between 8-Pmmn and metal substrates has so far remained unexplored, which has critical importance of its application in any electronic devices. Here, with the help of density functional theory, we show that the unique tilted-Dirac property is completely lost when 8-Pmmn borophene is interfaced with common electrode materials such as Au, Ag, and Ti. This is attributed to the high chemical reactivity of borophene as observed from crystal orbital Hamilton population and electron localization function analysis. In an effort to restore the Dirac property, we insert a graphene/hexagonal-boron-nitride (hBN) layer between 8-Pmmn and metal, a technique used in recent experiments for other 2D materials. We show that while the insertion of graphene successfully restores the Dirac nature for all three metals, hBN fails to do so while interfacing with Ti. The quantum chemical insights presented in this work may aid in to access the Dirac properties of 8-Pmmn in experiments.

FIG: (a) Top and side views of 3 × 3 × 1 supercell of 8-Pmmn borophene. The lattice parameters are a = 3.26 Å, b = 4.52 Å, and h = 2.19 Å. The inner and ridge atoms are denoted by blue and green atoms, respectively. (b) Crystal orbital Hamilton population (COHP) analysis and (c) electron localization function (ELF) plot for graphene and 8-Pmmn borophene.

Acknowledgments: The authors acknowledge the Supercomputer Education and Research Center (SERC), Indian Institute of Science (IISc), Bangalore, for CPU- and GPU-based computations. The computational charges were aided by the Mathematical Research Impact Centric Support (MATRICS) scheme of Science and Engineering Research Board (SERB), Government of India, under Grant No. MTR/2019/000047.