title: Transient Thermometry and High-Resolution Transmission Electron Microscopy Analysis of Filamentary Resistive Switches.
abstract: We present data on the filament size and temperature distribution in Hf0.82Al0.18Ox-based Resistive Random Access Memory (RRAM) devices obtained by transient thermometry and high-resolution transmission electron microscopy (HRTEM). The thermometry shows that the temperature of the nonvolatile conducting filament can reach temperatures as high as 1600 K at the onset of RESET at voltage of 0.8 V and power of 40 μW. The size of the filament was estimated at about 1 nm in diameter. Hot filament increases the temperature of the surrounding high resistivity oxide, causing it to conduct and carry a significant fraction of the total current. The current spreading results in slowing down the filament temperature increase at higher power. The results of thermometry have been corroborated by HRTEM analysis of the as-fabricated and switched RRAM devices. The functional HfAlOx layer in as-fabricated devices is amorphous. In devices that were switched, we detected a small crystalline region of 10-15 nm in size. The crystallization temperature of the HfAlOx was determined to be 850 K in an independent annealing experiment. The size of the crystalline region agrees with thermal modeling based on the thermometry data. Scanning transmission electron microscopy (TEM) coordinated with electron energy loss spectroscopy could not detect changes in the chemical makeup of the filament.
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Jonghan
authors.initials: J
authors.lastname: Kwon
authors.affiliation: Department of Electrical and Computer Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Abhishek A
authors.initials: AA
authors.lastname: Sharma
authors.affiliation: IMEC , Kapeldreef 75, Leuven 3001, Belgium.
authors.forename: Chao-Yang
authors.initials: CY
authors.lastname: Chen
authors.affiliation: IMEC , Kapeldreef 75, Leuven 3001, Belgium.
authors.forename: Andrea
authors.initials: A
authors.lastname: Fantini
authors.affiliation: IMEC , Kapeldreef 75, Leuven 3001, Belgium.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Jurczak
authors.affiliation: National Institute of Standards and Technology , Materials Measurement Laboratory, 100 Bureau Drive, Gaithersburg, Maryland 20899, United States.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Herzing
authors.affiliation: Department of Electrical and Computer Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
authors.forename: James A
authors.initials: JA
authors.lastname: Bain
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Yoosuf N
authors.initials: YN
authors.lastname: Picard
authors.affiliation: Department of Materials Science and Engineering, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States.
authors.forename: Marek
authors.initials: M
authors.lastname: Skowronski
keywords: HRTEM; RRAM; STEM-EELS; filament; thermometry