Phonons and excitons in ZrSe2-ZrS2alloys

Sean M. Oliver, Joshua J. Fox, Arsalan Hashemi, Akshay Singh, Randal L. Cavalero, Sam Yee, David W. Snyder, R. Jaramillo, Hannu Pekka Komsa, Patrick M. Vora

Research output: Contribution to journalArticle

Abstract

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−xusing 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−xbonds. 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 theΓ-point exciton binding energy at room temperature. This study illustrates the large effects of alloying on ZrSxSe2−xand lays the foundation for future applications of this material.

Original languageEnglish (US)
Pages (from-to)5732-5743
Number of pages12
JournalJournal of Materials Chemistry C
Volume8
Issue number17
DOIs
StatePublished - May 7 2020

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

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    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-ZrS2alloys. Journal of Materials Chemistry C, 8(17), 5732-5743. https://doi.org/10.1039/d0tc00731e