Characterzation of Ge-Sb-Te phase-change memory materials

Mihail Iovu; Eduard Colomeico; Vasile Benea; Diana Harea

doi:10.1117/12.981555

1 November 2012 Characterzation of Ge-Sb-Te phase-change memory materials

Mihail Iovu, Eduard Colomeico, Vasile Benea, Diana Harea

Proceedings Volume 8411, Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VI; 841103 (2012) https://doi.org/10.1117/12.981555
Event: Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies 2012, 2012, Constanta, Romania

Abstract

Phase-change memory materials are promising for the next generation of non-volatile flash memory that will serve in new mobile computing entertainment and other handheld electronics. Among them are chalcogenide glasses Ge-Sb-Te (GST) which can exist in two separate structural states – amorphous and crystalline. Switching of the material from one to another state can be done by heating applying an electrical pulse or by exposure to intense laser beam. In the present work we report the changes of optical parameters of amorphous Ge₁Sb₂Te₄, Ge₁Sb₄Te₇, and Ge₂Sb₂Te⁵ thin films under heat treatment and light exposure. The illumination with white during 1 hour does not change the transmission spectra of the as-deposited amorphous film. The spot of phase change transformation of the amorphous material was observed when the film was illuminated with UV laser pulses. From the transmission spectra T=f(λ) the optical constants (Absorption coefficient α, optical band gap E_g, refractive index n, the average electronic energy gap E0 and the dielectric oscillator strength E_d were calculated. For Ge₁Sb₂Te₄ the value of E₀ is smaller than optical band gap E_g=1.08 eV obtained from the Tauc plot. Large values of the refractive index n are obtained for smaller E₀=0.931 eV and for large E_d=7.448 eV. The anealing of the amorphous Ge₂Sb₂Te₅ thin film at T=100 ^oC during t=4 min shifts the transmission spectra in the low frequency region. The anealing at higher temperatures makes the thin film non-transparent, e.g. take place the process of crystalization.

Citation Download Citation

Mihail Iovu, Eduard Colomeico, Vasile Benea, and Diana Harea "Characterzation of Ge-Sb-Te phase-change memory materials", Proc. SPIE 8411, Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VI, 841103 (1 November 2012); https://doi.org/10.1117/12.981555

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