Epitaxial HfTe2 Dirac semimetal in the 2D limit

Polychronis Tsipas,Athanasios Dimoulas,Evgenia Symeonidou,Panagiotis Pappas,Christina Zacharaki,Evangelia Xenogiannopoulou,Sotirios Fragkos,Nikitas Siannas

doi:10.1063/5.0065839

Abstract

One monolayer semimetallic HfTe2 thin films are grown on three substrates with different electronic properties in order to study the substrate effect on the electronic structure of the HfTe2 epilayer. Angle resolved photoelectron spectroscopy measurements indicate that the band features are identical in all three cases, providing evidence that the HfTe2 epilayer does not interact with any of the substrates to form hybridized bands and any band feature originates from the HfTe2 material itself. However, a shift of HfTe2 energy bands is observed among the three cases, which is attributed to substrate electron doping. This paves the way for accessing the Dirac point of HfTe2 Dirac semimetal, which is located about ∼0.2 to 0.3 eV above the Fermi level in the case of suspended HfTe2 in a non-destructive way.

Highlights

Combined Reflection High-Energy Electron Diffraction (RHEED), Scanning Tunneling Microscopy (STM), and Angle Resolved Photoelectron Spectroscopy (ARPES) indicate that 1ML Hf Te2 is grown epitaxially on all three substrates and the valence bands exhibit a Dirac-like cone independent of the substrate, showing that these bands originate from the material itself and are not hybridized bands coming from the interaction between the epilayer and the substrate
The surface of the 1ML Hf Te2 epitaxial film grown on the Si(111)/InAs(111) substrate at the temperature of 450 ○C is investigated by in situ room temperature ultra-high vacuum (UHV)-STM (Fig. 1)
1ML Hf Te2 semimetallic films are grown on three different substrates, namely, Si(111)/InAs(111), SiC/graphene, and sapphire/MoS2 in order to study the substrate effect on the electronic properties of the Hf Te2 epilayer

Summary

Introduction

Topological materials have recently emerged and gained attention due to their unique electronic properties for realizing both fundamental physics and technological applications.1–10 A particular class of topologically non-trivial matter, known as “three dimensional (3D) graphene,” is the Dirac semimetals, which possess crossing linearly dispersive valence and conduction bands.11,12 To date, the majority of 3D Dirac semimetals has been grown by bulk methods and appears in the bulk form, while their epitaxial growth results in defective and discontinuous films.13–15 Only recently, it has been shown that high quality crystalline ZrTe2, Hf Te2, and HfxZr1−xTe2 thin films, whose electronic band structure exhibits similar behavior16–18 with the already proven 3D Dirac semimetals, can be grown epitaxially on InAs(111) and AlN(0001) substrates.Recent theoretical calculations19,20 predict that both ZrTe2 and Hf Te2 materials possess topological properties. A shift of Hf Te2 energy bands is observed among the three cases, which is attributed to substrate electron doping.

Results

Conclusion