First-principles structure determination of interface materials: The ${\text{Ni}}_{x}\text{InAs}$ nickelides

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First-principles structure determination of interface materials: The ${Ni}_{x} InAs$ nickelides

Georg Schusteritsch, Steven P. Hepplestone, and Chris J. Pickard

Phys. Rev. B 92, 054105 – Published 5 August 2015

Abstract

We present here a first-principles study of the ternary compounds formed by Ni, In, and As, a material of great importance for self-aligned metallic contacts in next-generation InAs-based MOS transistors. The approach we outline is general and can be applied to study the crystal structure and properties of a host of other new interface compounds. Using the ab initio random structure searching approach we find the previously unknown low-energy structures of ${Ni}_{x} InAs$ and assess their stability with respect to the known binary compounds of Ni, In, and As. Guided by experiments, we focus on ${Ni}_{3} InAs$ and find a rich energy landscape for this stoichiometry. We consider the five lowest-energy structures, with space groups $P m m n, P b c m, P 2_{1} / m, C m c m$ , and $R \bar{3}$ . The five low-energy structures for ${Ni}_{3} InAs$ are all found to be metallic and nonmagnetic. By comparison to previously published TEM results we identify the crystal structure observed in experiments to be $C m c m {Ni}_{3} InAs$ . We calculate the work function for $C m c m {Ni}_{3} InAs$ and, according to the Schottky-Mott model, expect the material to form an Ohmic contact with InAs. We further explicitly consider the interface between $C m c m {Ni}_{3} InAs$ and InAs and find it to be Ohmic with an $n -type$ Schottky barrier height of $- 0.55 eV$ .

Received 2 December 2014
Revised 9 April 2015

DOI:https://doi.org/10.1103/PhysRevB.92.054105

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

Authors & Affiliations

Georg Schusteritsch^1,*, Steven P. Hepplestone¹, and Chris J. Pickard^1,2

¹Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
²London Institute for Mathematical Sciences, 35a South Street, Mayfair, London W1K 2XF, United Kingdom

^*g.schusteritsch@ucl.ac.uk

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Vol. 92, Iss. 5 — 1 August 2015

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Figure 1
Ternary phase diagram of the Ni-In-As system shown at the top, with slices through the ternary convex hull shown at the bottom. Structures that are found to be stable are shown as red dots, while structures that do not fall onto the convex hull are shown as blue dots. Blue dots labeled $x = 1 - 6$ indicate the positions of the structures ${Ni}_{x} InAs$ on the ternary diagram. The left-hand side, center, and right-hand side plots at the bottom show the slices through the ternary phase diagram along InAs to Ni, As to Ni, and In to Ni, respectively. The slices through the ternary phase diagrams are shown as black solid lines, while the binary convex hull for InAs and Ni is shown as a black dashed line, with the gray line indicating the zero offset to the binary convex hull. ${Ni}_{3} InAs$ is found to be stable for the binary system InAs/Ni, while it is marginally unstable by $0.01 eV / atom$ on the ternary convex hull. The ternary phase diagram is based on a plot created using the stools analysis tool set [36].
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Figure 2
Unit cell of the five lowest-energy ${Ni}_{3} InAs$ structures labeled according to their space group. The relative energy of each structure with respect to the lowest-energy $P m m n$ structure is given in brackets. We also show the $C m c m$ structure overlaid on a zoomed-in image of the TEM results, which originally appeared in Ref. [5]. TEM image ©2012 IEEE. Reprinted, with permission, from Ref. [5]. Purple, green, and gray circles represent In, As, and Ni atoms, respectively.
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Figure 3
Electronic density of states of the five lowest-energy structures of ${Ni}_{3} InAs$ . All structures are found to have a nonzero value of the density of states at the Fermi level, showing their metallic nature. The Fermi energy is shown as a dashed gray vertical line. Gray dotted horizontal lines indicate the zero offset of the shifted curves.
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Figure 4
Density of states of $C m c m {Ni}_{3} InAs$ . The calculations were performed using the hybrid HSE functional and show metallic behavior further validating the results shown in Fig. 3.
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Figure 5
Partial density of states of $C m c m {Ni}_{3} InAs$ . The calculations show that the metallic behavior shown in Fig. 3 can be traced back to the Nickel atoms.
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Figure 6
Atomic structure of the ${InAs/Ni}_{3} InAs$ interface and the planar averaged electrostatic local reference potential, $\bar{V}$ , as a function of the perpendicular distance from the interface. The macroscopic average of the local reference potential is shown as dashed red and blue lines in the ${Ni}_{3} InAs$ and InAs regions, respectively. The Fermi energy of the ${Ni}_{3} InAs$ region is shown as a red solid line, while the conduction band minimum (CBM) of the InAs region is shown as a blue line. Only a small section of the total atomic structure of the interface is shown. Purple, green, and gray circles represent In, As, and Ni atoms, respectively.
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Physical Review B

covering condensed matter and materials physics

First-principles structure determination of interface materials: The ${Ni}_{x} InAs$ nickelides

Georg Schusteritsch, Steven P. Hepplestone, and Chris J. Pickard

Phys. Rev. B 92, 054105 – Published 5 August 2015

Abstract

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Article Text

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Physical Review B

covering condensed matter and materials physics

First-principles structure determination of interface materials: The NixInAs nickelides

Georg Schusteritsch, Steven P. Hepplestone, and Chris J. Pickard

Phys. Rev. B 92, 054105 – Published 5 August 2015

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First-principles structure determination of interface materials: The ${Ni}_{x} InAs$ nickelides