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Highly scalable non-volatile and ultra-low-power phase-change nanowire memory


The search for a universal memory storage device that combines rapid read and write speeds, high storage density and non-volatility is driving the exploration of new materials in nanostructured form1,2,3,4,5,6,7. Phase-change materials, which can be reversibly switched between amorphous and crystalline states, are promising in this respect, but top-down processing of these materials into nanostructures often damages their useful properties4,5. Self-assembled nanowire-based phase-change material memory devices offer an attractive solution owing to their sub-lithographic sizes and unique geometry, coupled with the facile etch-free processes with which they can be fabricated. Here, we explore the effects of nanoscaling on the memory-storage capability of self-assembled Ge2Sb2Te5 nanowires, an important phase-change material. Our measurements of write-current amplitude, switching speed, endurance and data retention time in these devices show that such nanowires are promising building blocks for non-volatile scalable memory and may represent the ultimate size limit in exploring current-induced phase transition in nanoscale systems.

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Figure 1: Structural characterization and electrical switching behaviour of Ge2Sb2Te5 nanowires.
Figure 2: Ge2Sb2Te5 nanowire size-dependent memory switching properties.
Figure 3: Recrystallization (data-retention) properties of a 60-nm Ge2Sb2Te5 nanowire.
Figure 4: Size-dependent recrystallization dynamics of Ge2Sb2Te5 nanowires with thickness ranging from 30 nm to 200 nm.


  1. Ovshinsky, S. R. Reversible electrical switching phenomena in disordered structures. Phys. Rev. Lett. 21, 1450–1453 (1968).

    Article  Google Scholar 

  2. Lai, S. & Lowrey, T. OUM-a 180 nm nonvolatile memory cell element technology for stand alone and embedded applications. IEDM Tech. Dig. 803–806 (2001).

  3. Pirovano, A. et al. Scaling analysis of phase-change memory technology. IEDM Tech. Dig. 699–702 (2003).

  4. Hudgens, S. & Johnson, B. Overview of phase-change chalcogenide nonvolatile memory technology. MRS Bull. 29, 829–832 (2004).

    Article  CAS  Google Scholar 

  5. Lee, S. H. et al. Full integration and cell characteristics for 64 Mb nonvolatile PRAM. Proc. Symp. VLSI Tech. Dig. 20–21 (2004).

  6. Lankhorst, M. H. R., Ketelaars, B. W. S. M. M. & Wolters, R. A. M. Low-cost and nanoscale non-volatile memory concept for future silicon chips. Nature Mater. 4, 347–352 (2005).

    Article  CAS  Google Scholar 

  7. Chen, Y. C. et al. Ultra-thin phase-change bridge memory device using GeSb. IEDM Tech. Dig. 1–3 (2006).

  8. Lieber, C. M. Nanoscale science and technology: building a big future from small things. MRS Bull. 28, 486–491 (2003).

    Article  CAS  Google Scholar 

  9. Agarwal, R. & Lieber, C. M. Semiconductor nanowires: optics and optoelectronics. Appl. Phys. A: Mater. Sci. Proc. 85, 209–215 (2006).

    Article  CAS  Google Scholar 

  10. Lee, S. H., Ko, D. K., Jung, Y. & Agarwal, R. Size-dependent phase transition memory switching behavior and low writing currents in GeTe nanowires. Appl. Phys. Lett. 89, 223116 (2006).

    Article  Google Scholar 

  11. Jung, Y., Lee, S. H., Ko, D. K. & Agarwal, R. Synthesis and characterization of Ge2Sb2Te5 nanowires with memory switching effect. J. Am. Chem. Soc. 128, 14026–14027 (2006).

    Article  CAS  Google Scholar 

  12. Yu, D., Wu, J., Gu, Q. & Park, H. Germanium telluride nanowires and nanohelices with memory-switching behavior. J. Am. Chem. Soc. 128, 8148–8149 (2006).

    Article  CAS  Google Scholar 

  13. Hwang, Y. N. et al. Full integration and reliability evaluation of phase-change RAM based on 0.24 µm-CMOS technologies. Proc. Symp. VLSI Tech. Dig. 173–174 (2003).

  14. Gill, M., Lowrey, T. & Park, J. Ovonic unified memory—a high-performance nonvolatile memory technology for stand alone and embedded applications. ISSCC Dig. Tech. Papers 202–203 (2002).

  15. Cho, W. Y. et al. A 0.18-µm 3.0-V 64-Mb nonvolatile phase-transition random access memory (PRAM). IEEE J. Solid-State Circ. 40, 293–300 (2005).

    Article  Google Scholar 

  16. Happ, T. D. et al. Novel one-mask self-heating pillar phase change memory. Proc. Symp. VLSI Tech. Dig. 120–121 (2006).

  17. Jeong, C. W. et al. Highly reliable ring-type contact for high-density phase change memory. Jpn. J. Appl. Phys. 45, 3233–3237 (2006).

    Article  CAS  Google Scholar 

  18. Privitera, S., Bongiorno, C. & Rimini, E. Crystal nucleation and growth processes in Ge2Sb2Te5 . Appl. Phys. Lett. 84, 4448–4450 (2004).

    Article  CAS  Google Scholar 

  19. Martens, H. C. F. & Vlutters, R. Thickness dependent crystallization speed in thin phase change layers used for optical recording. J. Appl. Phys. 95, 3977–3983 (2004).

    Article  CAS  Google Scholar 

  20. Khonik, V. A., Kitagawa, K. & Morii, H. On the determination of the crystallization activation energy of metallic glasses. J. Appl. Phys. 87, 8440–8443 (2000).

    Article  CAS  Google Scholar 

  21. Couchman, P. R. & Jesser, W. A. Thermodynamic theory of size dependence of melting temperature in metals. Nature 269, 481–483 (1977).

    Article  CAS  Google Scholar 

  22. Goldstein, A. N., Echer, C. M. & Alivisatos, A. P. Melting in semiconductor nanocrystals. Science 256, 1425–1427 (1992).

    Article  CAS  Google Scholar 

  23. Wu, Y. & Yang, P. Melting and welding semiconductor nanowires in nanotubes. Adv. Mater. 13, 520–523 (2001).

    Article  CAS  Google Scholar 

  24. Porter, D. A. & Eastering, K. E. in Phase Transformations in Metals and Alloys 2nd edn Ch. 5 (Chapman & Hall, London, 1992).

    Book  Google Scholar 

  25. Kalb, J. A., Wen, C. Y., Spaepen, F., Dieker, H. & Wuttig, M. Crystal morphology and nucleation in thin films of amorphous Te alloys used for phase change recording. J. Appl. Phys. 98, 054902 (2005).

    Article  Google Scholar 

  26. Jeong, T. H., Kim, M. R., Seo, H., Kim, S. J. & Kim, S. Y. Crystallization behavior of sputter-deposited amorphous Ge2Sb2Te5 thin films. J. Appl. Phys. 86, 774–778 (1999).

    Article  CAS  Google Scholar 

  27. Matsuzaki1, N. et al. Oxygen-doped GeSbTe phase-change memory cells featuring 1.5 V/100 µA standard 0.13 µm CMOS operations. IEDM Tech. Dig. 738–741 (2005).

  28. Horii, H. et al. A novel cell technology using N-doped GeSbTe films for phase change RAM. Proc. Symp. VLSI Tech. Dig. 177–178 (2003).

  29. Whang, D., Jin, S., Wu, Y. & Lieber, C. M. Large-scale hierarchical organization of nanowire arrays for integrated nanosystems. Nano Lett. 3, 1255–1259 (2003).

    Article  CAS  Google Scholar 

  30. Schmidt, V., Riel, H., Senz, S., Karg, S., Riess, W. & Gosele U. Realization of a silicon nanowire vertical surround-gate field-effect transistor. Small 2, 85–88 (2006).

    Article  CAS  Google Scholar 

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The authors would like to thank Hee-Suk Chung for helpful discussions. This work was supported by startup funds from the University of Pennsylvania, Materials Research Science & Engineering Center (MRSEC) seed award (DMR05-20020) and in part by NSF, DMR-0706381 and the University of Pennsylvania Research Foundation (URF) award.

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R.A., S.L. and Y.J. conceived and designed the experiments. Y.J. and S.L. performed the experiments. R.A., S.L. and Y.J. analysed the data. R.A., S.L. and Y.J. co-wrote the paper.

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Correspondence to Ritesh Agarwal.

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The authors declare no competing financial interests.

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Lee, SH., Jung, Y. & Agarwal, R. Highly scalable non-volatile and ultra-low-power phase-change nanowire memory. Nature Nanotech 2, 626–630 (2007).

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