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Observation of filament formation process of Cu/HfO2/Pt ReRAM structure by hard x-ray photoelectron spectroscopy under bias operation

Published online by Cambridge University Press:  20 January 2012

Takahiro Nagata ,
Masamitsu Haemori ,
Yoshiyuki Yamashita ,
Hideki Yoshikawa ,
Keisuke Kobayashi  and
Toyohiro Chikyow
Takahiro Nagata*
Affiliation:
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Ibaraki 305-0044, Japan
Masamitsu Haemori
Affiliation:
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Ibaraki 305-0044, Japan
Yoshiyuki Yamashita
Affiliation:
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Ibaraki 305-0044, Japan; and NIMS Beamline Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148, Japan
Hideki Yoshikawa
Affiliation:
NIMS Beamline Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148, Japan
Keisuke Kobayashi
Affiliation:
NIMS Beamline Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148, Japan
Toyohiro Chikyow
Affiliation:
International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Ibaraki 305-0044, Japan
*
a)Address all correspondence to this author. e-mail: NAGATA.Takahiro@nims.go.jp
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Abstract

We have demonstrated resistance switching using polycrystalline HfO2 film with a Cu top electrode for nonvolatile memory applications and revealed the Cu diffusion into the HfO2 layer during the filament formation process. Resistive switching was clearly observed in the Cu/HfO2/Pt structure by performing a current–voltage measurement. The current step from a high-resistive state to a low-resistive state was of the order of 103–104 Ω, which provided a sufficient on/off ratio for use as a switching device. The filament formation process was investigated by employing hard x-ray photoelectron spectroscopy under bias operation. The application of a bias to the structure reduced the Cu2O state at the interface and the intensity ratio of Cu 2p3/2/Hf 3d5/2, providing evidence of Cu2O reduction and Cu diffusion into the HfO2 layer. These results also provide evidence that the resistance switching of the Cu/HfO2/Pt structure originates in a solid electrolyte (nanoionics model) containing Cu ions.

Keywords

X-ray photoelectron spectroscopyOxideMemory
Type
Invited Feature Paper
Information
Journal of Materials Research , Volume 27 , Issue 6 , 28 March 2012 , pp. 869 - 878
Copyright
Copyright © Materials Research Society 2012

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