University of Oulu

Oliver, S. M., Fox, J. J., Hashemi, A., Singh, A., Cavalero, R. L., Yee, S., Snyder, D. W., Jaramillo, R., Komsa, H.-P., & Vora, P. M. (2020). Phonons and excitons in ZrSe2–ZrS2 alloys. Journal of Materials Chemistry C, 8(17), 5732–5743.

Phonons and excitons in ZrSe₂-ZrS₂ alloys

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Author: Oliver, Sean M.1,2; Fox, Joshua J.3,4; Hashemi, Arsalan5;
Organizations: 1Department of Physics and Astronomy, George Mason University, Fairfax, VA, USA
2Quantum Materials Center, George Mason University, Fairfax, VA, USA
3Electronic Materials and Devices Department, Applied Research Laboratory, Pennsylvania State University, University Park, Pennsylvania, USA
42-Dimensional Crystal Consortium, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, USA
5Department of Applied Physics, Aalto University, Aalto, Finland
6Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
7Department of Physics, Indian Institute of Science, Bangalore, India
8Microelectronics Research Unit, University of Oulu, Oulu, Finland
Format: article
Version: submitted version
Access: open
Online Access: PDF Full Text (PDF, 1.5 MB)
Persistent link:
Language: English
Published: Royal Society of Chemistry, 2020
Publish Date: 2020-06-15


Zirconium disulfide (ZrS2) and zirconium diselenide (ZrSe2) are promising materials for future optoelectronics due to indirect band gaps in the visible and near-infrared (NIR) spectral regions. Alloying these materials to produce ZrSxSe2−x (x = 0…2) would provide continuous control over key optical and electronic parameters required for device engineering. Here, we present a comprehensive analysis of the phonons and excitons in ZrSxSe2−x using low-temperature Raman spectroscopy and room-temperature spectroscopic ellipsometry (SE) measurements. We extract the Raman-active vibrational mode frequencies and find that they compare favorably with density functional theory (DFT) calculations. Our simulations and polarization-resolved measurements demonstrate that substitutional doping renders infrared (IR) modes to be Raman-active. This leads to a Raman spectrum dominated by nominally IR phonons, a phenomenon that originates from the large ionicity of the ZrSxSe2−x bonds. SE measurements of the complex refractive index quantify the blue-shift of direct, allowed exciton transitions with increasing S content, and we find strong light–matter interactions with low optical loss in the NIR. Correlating these data with DFT allows for an estimation of the Γ-point exciton binding energy at room temperature. This study illustrates the large effects of alloying on ZrSxSe2−x and lays the foundation for future applications of this material.

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Series: Journal of materials chemistry. C, Materials with applications in optical, magnetic & electronic devices
ISSN: 2050-7526
ISSN-E: 2050-7534
ISSN-L: 2050-7526
Volume: 8
Issue: 17
Pages: 5732 - 5743
DOI: 10.1039/d0tc00731e
Type of Publication: A1 Journal article – refereed
Field of Science: 116 Chemical sciences
216 Materials engineering
Funding: The work was financially supported by the National Science Foundation (NSF) through the Pennsylvania State University 2D Crystal Consortium - Materials Innovation Platform (2DCC-MIP) under NSF cooperative agreement DMR-1539916. P. Vora, S. Oliver, and S. Yee also acknowledge support from the George Mason University (GMU) Quantum Materials Center, the GMU Presidential Scholars Program, and the GMU Undergraduate Research Scholars Program. H. Komsa and A. Hashemi are grateful to the Academy of Finland for the support under Projects No. 286279 and 311058. H. Komsa and A. Hashemi also thank CSC–IT Center for Science Ltd. for generous grants of computer time. R. Jaramillo and A. Singh acknowledge support by an Office of Naval Research MURI through grant #N00014-17-1-2661.
Academy of Finland Grant Number: 286279
Detailed Information: 286279 (Academy of Finland Funding decision)
311058 (Academy of Finland Funding decision)
Copyright information: ©The Royal Society of Chemistry 2020. The Definitive Version of Record can be found online at: