Optical Properties of Se-Excess Ge2Sb2SexTe1 (4.23 < x < 4.97) Phase-Change Thin Films

Ji, Congzheng; Zheng, Fengang

doi:10.3390/cryst16090578

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Optical Properties of Se-Excess Ge₂Sb₂Se_xTe₁ (4.23 < x < 4.97) Phase-Change Thin Films

by

Congzheng Ji

¹ and

Fengang Zheng

^1,2,*

¹

School of Physical Science and Technology, Jiangsu Key Laboratory of Thin Films, Soochow University, Suzhou 215006, China

²

SJTU-Pinghu Institute of Intelligent Optoelectronics, Pinghu 314200, China

^*

Author to whom correspondence should be addressed.

Crystals 2026, 16(9), 578; https://doi.org/10.3390/cryst16090578

Submission received: 2 August 2026 / Revised: 2 September 2026 / Accepted: 2 September 2026 / Published: 4 September 2026

(This article belongs to the Section Inorganic Crystalline Materials)

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Abstract

In this study, Se-excess Ge₂Sb₂SeₓTe₁ (GSST) thin films were synthesized via magnetron co-sputtering. The crystal structure, surface morphology, complex refractive index, and bandgap of the Se-excess GSST thin films were systematically investigated. Owing to the formation of higher-energy Sb–Se bonds at an annealing temperature of 350 °C, grain refinement occurred (the average dendrite trunk width decreased from 0.64 μm to 0.37 μm). Consequently, the extinction coefficient (k) in the crystalline state was reduced to 0.17, resulting in a figure of merit (FOM) of 8.76 at the telecommunications C-band wavelength of 1550 nm.

Keywords: phase-change materials; GSST; optical materials and properties; Raman

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MDPI and ACS Style

Ji, C.; Zheng, F. Optical Properties of Se-Excess Ge₂Sb₂Se_xTe₁ (4.23 < x < 4.97) Phase-Change Thin Films. Crystals 2026, 16, 578. https://doi.org/10.3390/cryst16090578

AMA Style

Ji C, Zheng F. Optical Properties of Se-Excess Ge₂Sb₂Se_xTe₁ (4.23 < x < 4.97) Phase-Change Thin Films. Crystals. 2026; 16(9):578. https://doi.org/10.3390/cryst16090578

Chicago/Turabian Style

Ji, Congzheng, and Fengang Zheng. 2026. "Optical Properties of Se-Excess Ge₂Sb₂Se_xTe₁ (4.23 < x < 4.97) Phase-Change Thin Films" Crystals 16, no. 9: 578. https://doi.org/10.3390/cryst16090578

APA Style

Ji, C., & Zheng, F. (2026). Optical Properties of Se-Excess Ge₂Sb₂Se_xTe₁ (4.23 < x < 4.97) Phase-Change Thin Films. Crystals, 16(9), 578. https://doi.org/10.3390/cryst16090578

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

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Optical Properties of Se-Excess Ge₂Sb₂Se_xTe₁ (4.23 < x < 4.97) Phase-Change Thin Films

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