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Phonons and excitons in ZrSe2-ZrS2alloys

Oliver, SM and Fox, JJ and Hashemi, A and Singh, A and Cavalero, RL and Yee, S and Snyder, DW and Jaramillo, R and Komsa, HP and Vora, PM (2020) Phonons and excitons in ZrSe2-ZrS2alloys. In: Journal of Materials Chemistry C, 8 (17). pp. 5732-5743.

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Official URL: https://doi.org/10.1039/D0TC00731E


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 the�-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. © The Royal Society of Chemistry 2020.

Item Type: Journal Article
Publication: Journal of Materials Chemistry C
Publisher: Royal Society of Chemistry
Additional Information: The copyright for this article belongs to Authors
Keywords: Alloying; Binding energy; Blue shift; Energy gap; Excitons; Infrared devices; Phonons; Refractive index; Selenium compounds; Semiconductor quantum wells; Spectroscopic analysis; Spectroscopic ellipsometry; Sulfur compounds; Temperature; Zirconium compounds, Complex refractive index; Comprehensive analysis; Electronic parameters; Exciton transitions; Exciton-binding energy; Future applications; Light-matter interactions; Visible and near infrared, Density functional theory
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 03 Nov 2021 10:33
Last Modified: 03 Nov 2021 10:33
URI: http://eprints.iisc.ac.in/id/eprint/65485

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