Memory Effect in Simple Cu Nanogap Junction
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1250-G10-05
Memory Effect in Simple Cu Nanogap Junction Hiroshi Suga1, Masayo Horikawa1, Hisao Miyazaki2, Shunsuke Odaka2, Kazuhito Tsukagoshi2, Tetsuo Shimizu1, and Yasuhisa Naitoh1 1 Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki, Japan 2 Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, Japan ABSTRACT We have investigated the resistance switching effect in Cu nanogap junction. Nanogap structures were created by means of electromigration and their electrical properties were measured in a high vacuum chamber. The measured current-voltage characteristics exhibited a clear negative resistance and memory effect with a large on-off ratio of over 105. The estimation from I-V curves indicates that the resistance switching was caused by the gap size change, which implies that the nanogap switching (NGS) effect also occurs in Cu electrodes, a popular wiring material in an integrated circuit.
INTRODUCTION Resistive switching behavior of nanogap junction, which consists of two electrodes with a separation of about ten nanometer or below, is a very attractive subject of scientific and technical research.1 It was found that the nanogap junction exhibits a reversible resistance switching effect that is dependent on the intensity of the applied voltage between the nanogap junction. We call the switching effect the “nanogap switch” (NGS) effect. This NGS device is nonvolatile, and has the potential for application in future nonvolatile memory devices.2-4 It was suggested that the nonvolatile resistance changes in the NGS occur as a result of tunneling changes in gap width between the electrodes, which are caused by the applied bias voltage. Moreover, a clear negative differential resistance (NDR) is also shown in an I-V curve for all nanogap junctions that exhibit resistance switching. The NGS device has a wide selectivity for electrode materials such as various metals2, 4 silicon , and graphene5. Since copper is the most popular material for wiring material in the integration circuit 6, it is expected that the NGS device with Cu electrodes is very advantages for industrial applications. On the other hand, when the line and space between Cu wires is achieved at single nanoscale level in near future, a leakage may be caused by the NGS effect. Therefore, it is important to evaluate its nanoscale behavior, such as that in a resistance switch in Cu nanogap junctions. It is anticipated that Cu electrodes in Cu nanogap junctions will readily become coated with layers of insulative oxide. Therefore, the effect without oxide layers on the NGS effect should be investigated. In this letter, we investigated NGS effect in Cu nanogap junctions. In order to protect Cu surfaces form oxidization, the nanogap formations and electrical measurements were also carried out in the same vacuum chamber without exposing the samples to ambient air.
EXPERIMENT Figure 1 shows diag
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