Memories that constitute resistance as the state variable encompass a very broad range of materials and switching mechanisms.

Of these technologies, some, namely magnetic random access memory (MRAM), phase-change memory (PCM) and reduction/oxidation (redox) memories, have received more attention from the scientific community and the semiconductor industry and are thus in a more advanced state of research and/or development.

At IBM Research – Zurich, we are pursuing yet another resistive memory concept based on carbon.

Carbon-based memory could be a significant complement to the rapid advances in carbon-based nano-electronics. This could pave the way for potential all-carbon computing devices of the future.

The elemental nature of carbon would enable a carbon-based memory to be scaled down to very small feature sizes and to be immune to compositional changes that typically plague alternate multi-elemental non-volatile memory materials.

Moreover, the high resilience of carbon to a variety of external stimuli would ensure robustness and endurance of such a carbon-based memory.

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Evangelos Eleftheriou

Evangelos Eleftheriou

Department head, IBM Fellow

Stochastic phase-change neurons

Experimental studies using a conductive mode atomic force microscope demonstrated the ability to switch the resistance of carbon films down to tens of nanometers by the application of electrical pulses [1].

The thermal origins of this resistance change were firmly established by laser-pulse-induced resistance patterning and bulk annealing studies. Raman spectroscopy and NEXAFS spectroscopy allowed us to conclude that the resistance change is caused by the clustering of existing sp2 sites within the sp3 matrix.

We have also built nanoscale devices where reversible unipolar resistive switching was demonstrated by controlling the nanoscale graphitic filament formation and rupture with appropriate electrical pulses and built-in current compliance [2].

Our recent focus is on oxygenated amorphous carbon to address the issue of low endurance due to the difficulty of breaking the conductive carbon filaments. In oxygenated amorphous carbon, oxygen is added as a dopant to facilitate the breaking of the carbon filaments because it is known that carbon-based materials, when exposed to oxygen, break down in a process called Joule heating [4].

Publications

[1] A. Sebastian, A. Pauza, C. Rossel, R. M. Shelby, A. F. Rodriguez, H. Pozidis and E. Eleftheriou,
Resistance switching at the nanometre scale in amorphous carbon,” New Journal of Physics 13(1), 013020, 2011.

[2] L. Dellmann, A. Sebastian, P. Jonnalagada, C. A. Santini, W. W. Koelmans, C. Rossel and E. Eleftheriou,
Nonvolatile resistive memory devices based on hydrogenated amorphous carbon,” Proceedings of the IEEE European Solid-State Device Research Conference (ESSDERC), pp. 268-271, 2013.

[3] W.W. Koelmans and A. Sebastian,
“Carbon Memory: The Key Technical Challenges,” ITRS ERD Workshop, Albuquerque, 2014.

[4] C.A. Santini, A. Sebastian, C. Marchiori, V.P. Jonnalagadda, L. Dellmann, W.W. Koelmans, M.D. Rossell, C.P. Rossel and E. Eleftheriou,
Oxygenated amorphous carbon for resistive memory applications,” Nature Communications 6, 8600, 2015.

[5] W.W. Koelmans, T. Bachmann, F. Zipoli, A. K. Ott, C. Dou, A.C. Ferrari, O. Cojocaru-Mirédin, S. Zhang, M. Wuttig, V.K. Nagareddy, M.F. Craciun, A.M. Alexeev, C.D. Wright, V.P. Jonnalagadda, A. Curioni, A. Sebastian and E. Eleftheriou,
Carbon-based resistive memories,” International Memory Workshop, May 2016.