Structural transition and enhanced phase transition properties of Se doped Ge2Sb2Te5 alloys

Vinod Madhavan, K. Ramesh, K. S. Sangunni

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

Amorphous Ge2Sb2Te5 (GST) alloy, upon heating crystallize to a metastable NaCl structure around 150°C and then to a stable hexagonal structure at high temperatures (≥ 250°C). It has been generally understood that the phase change takes place between amorphous and the metastable NaCl structure and not between the amorphous and the stable hexagonal phase. In the present work, it is observed that the thermally evaporated (GST)1-x Sex thin films (0 ≤ x ≤ 0.50) crystallize directly to the stable hexagonal structure for x ≥ 0.10, when annealed at temperatures ≥ 150°C. The intermediate NaCl structure has been observed only for x <0.10. Chemically ordered network of GST is largely modified for x ≥ 0.10. Resistance, thermal stability and threshold voltage of the films are found to increase with the increase of Se. The contrast in electrical resistivity between the amorphous and crystalline phases is about 6 orders of magnitude. The increase in Se shifts the absorption edge to lower wavelength and the band gap widens from 0.63 to 1.05eV. Higher resistance ratio, higher crystallization temperature, direct transition to the stable phase indicate that (GST)1-x Sex films are better candidates for phase change memory applications.

Original languageEnglish
Article number8050
JournalScientific Reports
Volume5
DOIs
Publication statusPublished - 30 Jan 2015

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high resistance
threshold voltage
thermal stability
crystallization
electrical resistivity
heating
temperature
shift
electric potential
thin films
wavelengths

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Structural transition and enhanced phase transition properties of Se doped Ge2Sb2Te5 alloys. / Madhavan, Vinod; Ramesh, K.; Sangunni, K. S.

In: Scientific Reports, Vol. 5, 8050, 30.01.2015.

Research output: Contribution to journalArticle

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