Resistives Schalten in HfO2-basierten Metall-Isolator-Metall Strukturen für nicht-flüchtigen Speicher
Zusammenfassung der Projektergebnisse
The most important result of the project is the establishment of a unified model for the switching behavior of valence change based devices using HfO2 as dielectric and TiN as the active electrode. In metal-insulator-metal stacks where only the oxygen stoichiometry of the dielectric was changed, all reported switching modes could be reproduced. Based on the achieved experimental correlation of switching modes and material states, a unified model could be suggested, taking into account electrode field driven oxygen ions, thermophoresis due to temperature gradients and diffusion due to concentration gradients. A similar model could be applied for the closely related system of TaO-based devices. In addition, oxygen deficient samples allow to stabilize quantum point contacts where the conductance is given by one or a few conductance quanta observable at room-temperature. Other important results from a more technology point of view include the role of residual carbon inside the sample which may form under certain conditions carbon-carbon and carbon-hafnium bonds that cannot be broken and lead to irreparable device failure as well as the use of nano-guided filament approaches by nano-patterned electrode techniques to improve RRAM variability challenges. Future directions are direct visualization of conducting filaments by transmission electron microscopy which will allow the ultimate clarification of the nanoscopic switching mechanism, and the investigation of the devices with respect to neuromorphic functionality for which controlled gradual transitions between multiple conducting states are required.
Projektbezogene Publikationen (Auswahl)
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In-operando hard X-ray photoelectron spectroscopy study on the impact of current compliance and switching cycles on oxygen and carbon defects in resistive switching Ti/HfO2/TiN cells. J. Appl. Phys. 115, 204509 (2014)
M. Sowinska, T. Bertaud, D. Walczyk, S. Thiess, P. Calka, L. Alff, C. Walczyk, and T. Schroeder
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Thickness independent reduced forming voltage in oxygen engineered HfO2 based resistive switching memories. Appl. Phys. Lett. 105, 073505 (2014)
S. U. Sharath, J. Kurian, P. Komissinskiy, E. Hildebrandt, T. Bertaud, C. Walczyk, P. Calka, T. Schroeder, and L. Alff
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Towards forming-free resistive switching in oxygen engineered HfO2−x. Appl. Phys. Lett. 104, 063502 (2014)
S. U. Sharath, T. Bertaud, J. Kurian, E. Hildebrandt, C. Walczyk, P. Calka, P. Zaumseil, M. Sowinska, D. Walczyk, A. Gloskovskii, T. Schroeder, and L. Alff
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Geometric conductive filament confinement by nanotips for resistive switching of HfO2-RRAM devices with high performance. Sci. Rep. 6, 25757 (2016)
G. Niu, P. Calka, M. Auf der Maur, F. Santoni, S. Guha, M. Fraschke, P. Hamoumou, B. Gautier, E. Perez, C. Walczyk, C. Wenger, A. Di Carlo, L. Alff, and T. Schroeder
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Hafnium carbide formation in oxygen deficient hafnium oxide thin films. Appl. Phys. Lett. 108, 252903 (2016)
C. Rodenbuecher, E. Hildebrandt, K. Szot, S. U. Sharath, J. Kurian, P. Komissinskiy, U. Breuer, R. Waser, and L. Alff
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Impact of oxygen stoichiometry on electroforming and multiple switching modes in TiN/TaOx/Pt based ReRAM. Appl. Phys. Lett. 109, 173503 (2016)
S. U. Sharath, M. J. Joseph, S. Vogel, E. Hildebrandt, P. Komissinskiy, J. Kurian, T. Schroeder, and L. Alff
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Control of switching modes and conductance quantization in oxygen engineered HfOx based memristive devices. Adv. Funct. Mater. 27 1700432 (2017)
S. U. Sharath, S. Vogel, L. Molina-Luna, E. Hildebrandt, C. Wenger, J. Kurian, M. Duerrschnabel, T. Niermann, G. Niu, P. Calka, M. Lehmann, H.-J. Kleebe, T. Schroeder, and L. Alff
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Electron holography on HfO2/HfO2-x bilayer structures with multilevel resistive switching properties. Nanotechnology 28, 215702 (2017)
G. Niu, M. A. Schubert, S. U. Sharath, P. Zaumseil, S. Vogel, C. Wenger, E. Hildebrandt, S. Bhupathi, E. Perez, L. Alff, M. Lehmann, T. Schroeder, and T. Niermann
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Mechanism of the Key Impact of Residual Carbon Content on the Reliability of Integrated Resistive Random Access Memory Arrays. J. Phys. Chem. C 121, 7005–7014 (2017)
G. Niu, X. Cartoixà, A. Grossi, C. Zambelli, P. Olivo, E. Perez, M. A. Schubert, P. Zaumseil, I. Costina, T. Schroeder, and C. Wenger
