2019, Niu, Gang, Calka, Pauline, Huang, Peng, Sharath, Sankaramangalam Ulhas, Petzold, Stefan, Gloskovskii, Andrei, Fröhlich, Karol, Zhao, Yudi, Kan, Jinfeng, Schubert, Markus Andreas, Bärwolf, Florian, Ren, Wei, Ye, Zuo-Guang, Perez, Eduardo, Wenger, Christian, Alff, Lambert, Schroeder, Thomas

The HfO2-based resistive random access memory (RRAM) is one of the most promising candidates for non-volatile memory applications. The detection and examination of the dynamic behavior of oxygen ions/vacancies are crucial to deeply understand the microscopic physical nature of the resistive switching (RS) behavior. By using synchrotron radiation based, non-destructive and bulk-sensitive hard X-ray photoelectron spectroscopy (HAXPES), we demonstrate an operando diagnostic detection of the oxygen ‘breathing’ behavior at the oxide/metal interface, namely, oxygen migration between HfO2 and TiN during different RS periods. The results highlight the significance of oxide/metal interfaces in RRAM, even in filament-type devices. IMPACT STATEMENT: The oxygen ‘breathing’ behavior at the oxide/metal interface of filament-type resistive random access memory devices is operandoly detected using hard X-ray photoelectron spectroscopy as a diagnostic tool. © 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

2016, Niu, Gang, Calka, Pauline, Auf der Maur, Matthias, Santoni, Francesco, Guha, Subhajit, Fraschke, Mirko, Hamoumou, Philippe, Gautier, Brice, Perez, Eduardo, Walczyk, Christian, Wenger, Christian, Di Carlo, Aldo, Alff, Lambert, Schroeder, Thomas

Filament-type HfO2-based RRAM has been considered as one of the most promising candidates for future non-volatile memories. Further improvement of the stability, particularly at the “OFF” state, of such devices is mainly hindered by resistance variation induced by the uncontrolled oxygen vacancies distribution and filament growth in HfO2 films. We report highly stable endurance of TiN/Ti/HfO2/Si-tip RRAM devices using a CMOS compatible nanotip method. Simulations indicate that the nanotip bottom electrode provides a local confinement for the electrical field and ionic current density; thus a nano-confinement for the oxygen vacancy distribution and nano-filament location is created by this approach. Conductive atomic force microscopy measurements confirm that the filaments form only on the nanotip region. Resistance switching by using pulses shows highly stable endurance for both ON and OFF modes, thanks to the geometric confinement of the conductive path and filament only above the nanotip. This nano-engineering approach opens a new pathway to realize forming-free RRAM devices with improved stability and reliability.