Epitaxial growth and air-stability of monolayer Cu₂Te*

Abstract

A new two-dimensional atomic crystal, monolayer cuprous telluride (Cu 2 Te) has been fabricated on a graphene-SiC(0001) substrate by molecular beam epitaxy (MBE). The low-energy electron diffraction (LEED) characterization shows that the monolayer Cu 2 Te forms a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msqrt> <mml:mn>3</mml:mn> </mml:msqrt> <mml:mo>×</mml:mo> <mml:msqrt> <mml:mn>3</mml:mn> </mml:msqrt> </mml:mrow> </mml:math> superstructure with respect to the graphene substrate. The atomic structure of the monolayer Cu 2 Te is investigated through a combination of scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations. The stoichiometry of the Cu 2 Te sample is verified by x-ray photoelectron spectroscopy (XPS) measurement. The angle-resolved photoemission spectroscopy (ARPES) data present the electronic band structure of the sample, which is in good agreement with the calculated results. Furthermore, air-exposure experiments reveal the chemical stability of the monolayer Cu 2 Te. The fabrication of this new 2D material with a particular structure may bring new physical properties for future applications.