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p-type behavior of CrN thin films via control of point defects

Arnaud le Febvrier, Davide Gambino, Fabien Giovannelli, Babak Bakhit, Simon Hurand, Gregory Abadias, Björn Alling, and Per Eklund
Phys. Rev. B 105, 104108 – Published 16 March 2022
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Abstract

We report the results of a combined experimental and theoretical study on nonstoichiometric CrN1+δ thin films grown by reactive magnetron sputtering on c-plane sapphire and MgO (100) substrates in an Ar/N2 gas mixture using different percentages of N2. There is a transition from n-type to p-type behavior in the layers as a function of nitrogen concentration varying from 48 to 52 at. % in CrN films. The compositional change follows a similar trend for all substrates, with a N/Cr ratio increasing from approximately 0.7 to 1.06–1.11 by increasing the percentage of N2 in the gas flow ratio. As a result of the change in stoichiometry, the lattice parameter and the Seebeck coefficient increase together with the increase of N in CrN1+δ; in particular, the Seebeck value coefficient transitions from 50μVK1 for CrN0.97 to +75μVK1 for CrN1.1. Density functional theory calculations show that Cr vacancies can account for the change in the Seebeck coefficient, since they push the Fermi level down in the valence band, whereas N interstitial defects in the form of N2 dumbbells are needed to explain the increasing lattice parameter. Calculations including both types of defects, which have a strong tendency to bind together, reveal a slight increase in the lattice parameter and a simultaneous formation of holes in the valence band. To explain the experimental trends, we argue that both Cr vacancies and N2 dumbbells, possibly in combined configurations, are present in the films. We demonstrate the possibility of controlling the semiconducting behavior of CrN with intrinsic defects from n to p type, opening possibilities to integrate this compound in energy-harvesting thermoelectric devices.

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  • Received 16 November 2021
  • Revised 10 January 2022
  • Accepted 25 February 2022

DOI:https://doi.org/10.1103/PhysRevB.105.104108

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Arnaud le Febvrier1,*, Davide Gambino1,†, Fabien Giovannelli2, Babak Bakhit1, Simon Hurand3, Gregory Abadias3, Björn Alling1, and Per Eklund1

  • 1Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden
  • 2GREMAN UMR-CNRS 7347, Université de Tours, INSA Centre Val de Loire, 15 Rue de la Chocolaterie, CS 2903, 41029 Blois Cedex, France
  • 3Institut Pprime, Département de Physique et Mécanique des Matériaux, UPR 3346, CNRS–Université de Poitiers–ENSMA, Boulevard Marie et Pierre Curie 11, TSA 41123, 86073 Poitiers Cedex 9, France

  • *arnaud.le.febvrier@liu.se
  • davide.gambino@liu.se

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Issue

Vol. 105, Iss. 10 — 1 March 2022

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