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Proceedings Paper

Characterzation of Ge-Sb-Te phase-change memory materials
Author(s): Mihail Iovu; Eduard Colomeico; Vasile Benea; Diana Harea
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Paper 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 Eg, refractive index n, the average electronic energy gap E0 and the dielectric oscillator strength Ed were calculated. For Ge1Sb2Te4 the value of E0 is smaller than optical band gap Eg=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 Ed=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.

Paper Details

Date Published: 1 November 2012
PDF: 6 pages
Proc. SPIE 8411, Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VI, 841103 (1 November 2012); doi: 10.1117/12.981555
Show Author Affiliations
Mihail Iovu, Institute of Applied Physics (Moldova)
Eduard Colomeico, Institute of Applied Physics (Moldova)
Vasile Benea, Institute of Applied Physics (Moldova)
Diana Harea, Institute of Applied Physics (Moldova)

Published in SPIE Proceedings Vol. 8411:
Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VI
Paul Schiopu; Razvan Tamas, Editor(s)

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