The Critical Role of Anharmonic Lattice Dynamics for Macroscopic Properties of the Visible Light Absorbing Nitride Semiconductor CuTaN2

Franziska S. Hegner, Adi Cohen, Stefan S. Rudel, Silva M. Kronawitter, Manuel Grumet, Xiangzhou Zhu, Roman Korobko, Lothar Houben, Chang Ming Jiang, Wolfgang Schnick, Gregor Kieslich, Omer Yaffe, Ian D. Sharp, David A. Egger

Research output: Contribution to journalArticlepeer-review

Abstract

Ternary nitride semiconductors are rapidly emerging as a promising class of materials for energy conversion applications, offering an appealing combination of strong light absorption in the visible range, desirable charge transport characteristics, and good chemical stability. In this work, it is shown that finite-temperature lattice dynamics in CuTaN2 – a prototypical ternary nitride displaying particularly strong visible light absorption – exhibit a pronounced anharmonic character that plays an essential role in defining its macroscopic optoelectronic and thermal properties. Low-frequency vibrational modes that are Raman-inactive from symmetry considerations of the average crystal structure and unstable in harmonic phonon calculations are found to appear as intensive Raman features near room temperature. The atomic contributions to the anharmonic vibrations are characterized by combining Raman measurements with molecular dynamics and density functional theory calculations. This analysis reveals that anharmonic lattice dynamics have large ramifications on the fundamental properties of this compound, resulting in uniaxial negative thermal expansion and the opening of its bandgap to a near-optimal value for solar energy harvesting. The atomic-level understanding of anharmonic lattice dynamics, as well as the finding that they strongly influence key properties of this semiconductor at room temperature, have important implications for design of new functional materials, especially within the emerging class of ternary nitride semiconductors.

Original languageEnglish
Article number2303059
JournalAdvanced Energy Materials
Volume14
Issue number19
DOIs
StatePublished - 17 May 2024
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2024 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH.

Keywords

  • anharmonic lattice dynamics
  • molecular dynamics
  • nitrides
  • optoelectronic properties
  • raman spectroscopy

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