The Critical Role of Anharmonic Lattice Dynamics for Macroscopic Properties of the Visible Light Absorbing Nitride Semiconductor CuTaN2
Journal
Advanced Energy Materials
Date Issued
2024-01-01
Author(s)
Hegner, Franziska S.
Cohen, Adi
Rudel, Stefan S.
Kronawitter, Silva M.
Grumet, Manuel
Zhu, Xiangzhou
Korobko, Roman
Houben, Lothar
Schnick, Wolfgang
Kieslich, Gregor
Yaffe, Omer
Sharp, Ian D.
Egger, David A.
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.
Subjects
anharmonic lattice dynamics | molecular dynamics | nitrides | optoelectronic properties | raman spectroscopy
Type
journal article