Dependence of the electronic and transport properties of ${\text{metal-MoSe}}_{2}$ interfaces on contact structures

Dependence of the electronic and transport properties of ${metal-MoSe}_{2}$ interfaces on contact structures

Deniz Çakır and F. M. Peeters

Phys. Rev. B 89, 245403 – Published 4 June 2014

Abstract

Transition metal dichalcogenides (TMDs) are considered as promising candidates for next generation of electronic and optoelectronic devices. To make use of these materials, for instance in field effect transistor applications, it is mandatory to know the detailed properties of contacts of such TMDs with metal electrodes. Here, we investigate the role of the contact structure on the electronic and transport properties of ${metal-MoSe}_{2}$ interfaces. Two different contact types, namely face and edge contacts, are studied. We consider both low (Sc) and high (Au) work function metals in order to thoroughly elucidate the role of the metal work function and the type of metal. First principles plane wave calculations and transport calculations based on nonequilibrium Green's function formalism reveal that the contact type has a large impact on the electronic and transport properties of ${metal-MoSe}_{2}$ interfaces. For the Sc electrode, the Schottky barrier heights are around 0.25 eV for face contact and bigger than 0.6 eV for edge contact. For the Au case, we calculate very similar barrier heights for both contact types with an average value of 0.5 eV. Furthermore, while the face contact is found to be highly advantageous as compared to the edge contact for the Sc electrode, the latter contact becomes a better choice for the Au electrode. Our findings provide guidelines for the fabrication of TMD-based devices.

Received 27 February 2014
Revised 13 May 2014

DOI:https://doi.org/10.1103/PhysRevB.89.245403

Authors & Affiliations

Deniz Çakır^* and F. M. Peeters^†

Department of Physics, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium

^*deniz.cakir@uantwerpen.be
^†francois.peeters@uantwerpen.be

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Vol. 89, Iss. 24 — 15 June 2014

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Figure 1
Optimized lowest energy structures of the MoSe $_{2}$ monolayer contacted to the Sc(0001) surface from different views used in the electronic structure and transport calculations. In (a) edge contact with zigzag termination, in (b) edge contact with armchair termination, and face contact in (c). The physical separation is the distance between the topmost layer of the metal electrode and topmost layer of the MoSe $_{2}$ monolayer at the interface. The $z$ direction is the transport direction in the Transiesta calculations. Shaded parts show the electrode regions. Figures are prepared using the vesta program [32].
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Figure 2
Partial density of states of (a) free standing MoSe $_{2}$ , (b) edge contacted MoSe $_{2}$ with zigzag termination, (c) armchair termination, and (d) face contacted MoSe $_{2}$ , as calculated with vasp. Vertical dashed line denotes the Fermi level. In (a) black solid, blue dotted, and red dashed curves show the projection of the total DOS on MoSe $_{2}$ , Mo, and Se, respectively. In (b), (c), and (d) we plot projection of the total DOS on different Mo and Se atoms. Here, Mo $_{n b}$ (blue line) and Mo $_{b}$ (dashed blue line) are used to show the molybdenum atoms far away from interface and at the interface, respectively. Similarly, Se $_{n b}$ (red line) and Se $_{b}$ (dashed red line) are the selenium atoms far away from interface and at the interface, respectively. The PDOS of the Mo $_{n b}$ , Mo $_{b}$ , Se $_{n b}$ , and Se $_{b}$ atoms is enlarged in order to make them visible.
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Figure 3
Top and side views of the energy resolved charge densities for (a) edge contact with armchair termination and (b) face contact. The charge densities associated with states in the energy range of $E_{F} - 0.25 eV < E < E_{F} + 0.25$ eV. Here, $E_{F}$ is the Fermi level. The value of isosurface is 0.005 $e$ /Å $^{3}$ . The charge density is superimposed to the ball-and-stick model. Figures are prepared using the vesta program [32].
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Figure 4
Partial density of states of (a) the edge contacted MoSe $_{2}$ with zigzag termination and (b) the face contacted MoSe $_{2}$ for the Au electrode, as calculated with vasp. Vertical dashed line denotes the Fermi level. We plot the projection of the total DOS on the different Mo and Se atoms. Here, Mo $_{n b}$ (blue line) and Mo $_{b}$ (dashed blue line) are used to show the molybdenum atoms far away from interface and at the interface, respectively. Similarly, Se $_{n b}$ (red line) and Se $_{b}$ (dashed red line) are the selenium atoms far away from interface and at the interface, respectively. The PDOS of the Mo $_{n b}$ , Mo $_{b}$ , Se $_{n b}$ , and Se $_{b}$ atoms is enlarged in order to make them visible.
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Figure 5
Transmission for edge contact (a) in zigzag termination, (b) in armchair termination, and (c) face contact at zero bias, as calculated with Transiesta. The zero of energy is at the Fermi level $E_{F}$ indicated by the vertical dashed lines.
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Figure 6
Current per total area covered by MoSe $_{2}$ monolayer on the Sc surface in the device region as a function of voltage for face contact (filled black circles) and edge contact with armchair termination (filled red squares). The area of the MoSe $_{2}$ monolayer in the device region directly contacted to the Sc surface in the face (edge) contact geometry is 28.65 (20.74) Å $^{2}$ . In the inset, to compare the current of edge contact with that of face contact on a similar scale we multiple it with 40.
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Physical Review B

covering condensed matter and materials physics

Dependence of the electronic and transport properties of ${metal-MoSe}_{2}$ interfaces on contact structures

Deniz Çakır and F. M. Peeters

Phys. Rev. B 89, 245403 – Published 4 June 2014

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Physical Review B

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Dependence of the electronic and transport properties of metal-MoSe2 interfaces on contact structures

Deniz Çakır and F. M. Peeters

Phys. Rev. B 89, 245403 – Published 4 June 2014

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Dependence of the electronic and transport properties of ${metal-MoSe}_{2}$ interfaces on contact structures