Structural and Electronic Properties of Germanene on ${\mathrm{MoS}}_{2}$

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Structural and Electronic Properties of Germanene on ${MoS}_{2}$

L. Zhang, P. Bampoulis, A. N. Rudenko, Q. Yao, A. van Houselt, B. Poelsema, M. I. Katsnelson, and H. J. W. Zandvliet

Phys. Rev. Lett. 116, 256804 – Published 21 June 2016; Erratum Phys. Rev. Lett. 117, 059902 (2016)

See Synopsis: A Good Match for Germanene

Abstract

To date germanene has only been synthesized on metallic substrates. A metallic substrate is usually detrimental for the two-dimensional Dirac nature of germanene because the important electronic states near the Fermi level of germanene can hybridize with the electronic states of the metallic substrate. Here we report the successful synthesis of germanene on molybdenum disulfide ( ${MoS}_{2}$ ), a band gap material. Preexisting defects in the ${MoS}_{2}$ surface act as preferential nucleation sites for the germanene islands. The lattice constant of the germanene layer ( $3.8 \pm 0.2 Å$ ) is about 20% larger than the lattice constant of the ${MoS}_{2}$ substrate (3.16 Å). Scanning tunneling spectroscopy measurements and density functional theory calculations reveal that there are, besides the linearly dispersing bands at the $K$ points, two parabolic bands that cross the Fermi level at the $Γ$ point.

Received 24 January 2016

DOI:https://doi.org/10.1103/PhysRevLett.116.256804

Physics Subject Headings (PhySH)

Dichalcogenides Germanene

Scanning electron microscopy Scanning tunneling spectroscopy

Condensed Matter, Materials & Applied Physics

Erratum

Erratum: Structural and Electronic Properties of Germanene on ${MoS}_{2}$ [Phys. Rev. Lett. 116, 256804 (2016)]

L. Zhang, P. Bampoulis, A. N. Rudenko, Q. Yao, A. van Houselt, B. Poelsema, M. I. Katsnelson, and H. J. W. Zandvliet

Phys. Rev. Lett. 117, 059902 (2016)

Synopsis

A Good Match for Germanene

Published 21 June 2016

Germanene—the germanium analog of graphene—can remain a topological insulator when placed on a molybdenum disulfide substrate.

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Authors & Affiliations

L. Zhang¹, P. Bampoulis¹, A. N. Rudenko², Q. Yao¹, A. van Houselt¹, B. Poelsema¹, M. I. Katsnelson², and H. J. W. Zandvliet^1,*

¹Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
²Institute for Molecules and Materials, Radboud University, Heijendaalseweg 135, 6525 AJ Nijmegen, The Netherlands

^*Corresponding author. h.j.w.zandvliet@utwente.nl

$Z_{2}$ Invariance of Germanene on ${MoS}_{2}$ from First Principles

Taher Amlaki, Menno Bokdam, and Paul J. Kelly

Phys. Rev. Lett. 116, 256805 (2016)

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Vol. 116, Iss. 25 — 24 June 2016

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Figure 1
(a) Scanning tunneling microscopy image of the ${MoS}_{2}$ substrate. Inset: small scale image revealing the honeycomb structure of ${MoS}_{2}$ (obtained after a fast Fourier transform operation of the raw data). The set points are 0.2 V and 1 nA, respectively. (b) Scanning tunneling microscopy image of the ${MoS}_{2}$ surface after the deposition of $\sim 10 %$ of a monolayer of germanium at room temperature. Small germanium islands are nucleated at preexisting defect sites of the ${MoS}_{2}$ substrate. The set points are 0.5 V and 0.6 nA, respectively.
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Figure 2
(a) Scanning tunneling microscopy image of the ${MoS}_{2} / germanium$ substrate. The sample bias is 0.5 V and the tunneling current is 0.3 nA. (b) A zoom-in on a bare ${MoS}_{2}$ area. The STM image reveals a honeycomb structure with a lattice constant of $3.15 \pm 0.2 Å$ , which corresponds to the lattice constant of ${MoS}_{2}$ . The sample bias and the tunneling current are the same as in (a). (c) A zoom-in on the large germanene island of panel (a) reveals a hexagonal lattice with a lattice constant of $3.8 \pm 0.2 Å$ . The sample bias and the tunneling current are the same as in (a). (d) Differential conductivity recorded on a germanene island (black curve) and the surrounding ${MoS}_{2}$ surface (red curve). The set points are 1 V and 0.3 nA. (e) Line scan taken across the germanene island indicated with the blue dashed line in (a). The apparent height of the germanene islands is $\sim 3.2 Å$ . (f) Line scan taken on top of the germanene island indicated with the red dashed line in (a). The measured lattice constant of the germanene island corresponds to $3.8 \pm 0.2 Å$ . (g)–(h) Ball and stick models of germanene and ${MoS}_{2}$ . Top views (g) and side views (h).
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Figure 3
(a) A continuous film of germanene on ${MoS}_{2}$ after the deposition of about a monolayer of germanium. The sample bias and tunnel current are $- 1 V$ and 0.3 nA, respectively. (b) Left: ball-and-stick model. Large (small) circles represent upward (downward) buckled germanium atoms. Right: High-resolution scanning tunneling microscopy image of germanene (only the upward buckled germanium atoms are resolved). (c) Differential conductivity recorded on the germanene film. The set points are $- 1.4 V$ and 0.6 nA, respectively.
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Figure 4
Calculated total and partial densities of states of germanene on ${MoS}_{2}$ . Vertical solid and dashed lines correspond to the Fermi energy and Dirac point, respectively.
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Figure 5
Band structure shown along the high-symmetry points of the Brillouin zone and the corresponding orbital-resolved density of states calculated for contracted germanene with a lattice constant $a_{Ge} = 3.82 Å$ and a buckling parameter $Δ = 0.86 \pm 0.10 Å$ . Horizontal solid and dashed lines correspond to the Fermi energy and Dirac point, respectively. Green and blue circles mark the $π$ and $σ$ bands, respectively.
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Physical Review Letters

Structural and Electronic Properties of Germanene on ${MoS}_{2}$

L. Zhang, P. Bampoulis, A. N. Rudenko, Q. Yao, A. van Houselt, B. Poelsema, M. I. Katsnelson, and H. J. W. Zandvliet

Phys. Rev. Lett. 116, 256804 – Published 21 June 2016; Erratum Phys. Rev. Lett. 117, 059902 (2016)

See Synopsis: A Good Match for Germanene

Abstract

Physics Subject Headings (PhySH)

Erratum

Erratum: Structural and Electronic Properties of Germanene on ${MoS}_{2}$ [Phys. Rev. Lett. 116, 256804 (2016)]

L. Zhang, P. Bampoulis, A. N. Rudenko, Q. Yao, A. van Houselt, B. Poelsema, M. I. Katsnelson, and H. J. W. Zandvliet

Phys. Rev. Lett. 117, 059902 (2016)

Synopsis

A Good Match for Germanene

Published 21 June 2016

Authors & Affiliations

See Also

$Z_{2}$ Invariance of Germanene on ${MoS}_{2}$ from First Principles

Taher Amlaki, Menno Bokdam, and Paul J. Kelly

Phys. Rev. Lett. 116, 256805 (2016)

Article Text (Subscription Required)

References (Subscription Required)

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Physical Review Letters

Structural and Electronic Properties of Germanene on MoS2

L. Zhang, P. Bampoulis, A. N. Rudenko, Q. Yao, A. van Houselt, B. Poelsema, M. I. Katsnelson, and H. J. W. Zandvliet

Phys. Rev. Lett. 116, 256804 – Published 21 June 2016; Erratum Phys. Rev. Lett. 117, 059902 (2016)

See Synopsis: A Good Match for Germanene

Abstract

Physics Subject Headings (PhySH)

Erratum

Erratum: Structural and Electronic Properties of Germanene on MoS2 [Phys. Rev. Lett. 116, 256804 (2016)]

L. Zhang, P. Bampoulis, A. N. Rudenko, Q. Yao, A. van Houselt, B. Poelsema, M. I. Katsnelson, and H. J. W. Zandvliet

Phys. Rev. Lett. 117, 059902 (2016)

Synopsis

A Good Match for Germanene

Published 21 June 2016

Authors & Affiliations

See Also

Z2 Invariance of Germanene on MoS2 from First Principles

Taher Amlaki, Menno Bokdam, and Paul J. Kelly

Phys. Rev. Lett. 116, 256805 (2016)

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Structural and Electronic Properties of Germanene on ${MoS}_{2}$

Erratum: Structural and Electronic Properties of Germanene on ${MoS}_{2}$ [Phys. Rev. Lett. 116, 256804 (2016)]

$Z_{2}$ Invariance of Germanene on ${MoS}_{2}$ from First Principles