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Reversible Conductivity Transformations in Chalcogenide Alloy Films

  • E. J. Evans
  • J. H. Helbers
  • S. R. Ovshinsky
Part of the Institute for Amorphous Studies Series book series (IASS)

Abstract

Certain amorphous chalcogenide alloys, such as Ge15Te85, exhibit metastable conductivity. These reversible structural changes in amorphous alloys entailing variation in order and conductivity have been made the basis of memory devices.(1) In this paper, we present our observations on induced conductivity transformation from one state to another. Because the conductivity involves structural changes in the bulk we relate our results to those obtained from calorimetric (2) and structural investigation (3) on the same materials. We also present measurements on the electrical characteristics of memory switches.

Keywords

Threshold Voltage Amorphous Alloy Conductive State High Resistance State Memory Material 
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References

  1. 1.
    S.R. Ovshinsky, Phys. Rev. Lett. 21 (1968) 1450; also U.S. Patent No. 3,271,591.ADSCrossRefGoogle Scholar
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    H. Fritzsche and S.R. Ovshinsky, J. Non-Crystalline Solids 2 (1970) 148.ADSCrossRefGoogle Scholar
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    The dilatometric and calorimetric measurements were made on bulk samples whereas the resistivity measurements were taken on sputtered films. There is no certainty that the composition of the samples was identical. In addition, bulk samples used for the dilatometric studies were cooled from the melt and hence are expected to have different structure from films deposited on cold substrates.Google Scholar
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    It is not implied that considerably more energy is required to SET than RESET. Since the thermal time constant of the thin-film sample on glass is shorter than the minimum flashlamp pulse width, the energy lost from the broad pulse will be significantly higher than the narrow-pulse due to heat conduction. The indicated energy is flashlamp input and has not been quantitatively related to absorbed energy in the sample. Electrical pulse measurements indicate that RESET and SET energies are comparable.Google Scholar
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    R.G. Neale, J. Non-Crystalline Solids 2 (1970) 558.ADSCrossRefGoogle Scholar
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    H. Fritzsche, Physics of Instabilities in Amorphous Semiconductors, presented at Symp. on Instabilities in Semiconductors, IBM, Watson Res. Lab., Yorktown Heights, N.Y. (1969).Google Scholar
  8. 8.
    S.R. Ovshinsky, Ovonic Switching Devices, presented at Intern. Colloq. on Amorphous and Liquid Semiconductors, Bucharest, Rumania (1967).Google Scholar

Copyright information

© Plenum Press, New York 1991

Authors and Affiliations

  • E. J. Evans
    • 1
  • J. H. Helbers
    • 1
  • S. R. Ovshinsky
    • 1
  1. 1.Energy Conversion Devices, Inc.TroyUSA

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