Studies on Control of Oxygen Vacancies in MOD-made BaTiO 3 Thin Film by Nitrogen Annealing to Improve Resistive Switchin
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Studies on Control of Oxygen Vacancies in MOD-made BaTiO3 Thin Film by Nitrogen Annealing to Improve Resistive Switching Behavior for ReRAM Application S. Maejima, T. Sugie, K. Yamashita, and M. Noda Kyoto Institute of Technology, Sakyo-ku Matsugasaki Kyoto, Japan ABSTRACT Metal Organic Decomposition (MOD)-made BaTiO3 (BT) thin films were prepared for Resistive Random Access Memory (ReRAM) under various annealing conditions and investigated for improving the properties of bipolar-type resistive switching, focusing on the relation between oxygen vacancies and the behavior of resistive hysteresis. BT thin films with both pre- and final- annealing in nitrogen showed the resistive hysteresis of bipolar-type switching with current ON/OFF ratios of 2 orders of magnitude for both bias polarities. Finally they showed the endurance property with the 106 switching cycles. It was suggested that oxygen vacancies near the oxide surface (both interfaces at metal electrode/oxide and between layer-bylayered oxide layers) are increased by N2 annealing and enhanced the interface-type resistive switching. Pre-annealing in N2 was also found to be very effective to improve endurance properties, implying that not only the electrode/oxide interface but also the middle part of the film would contribute the interface-type mechanism.
INTRODUCTION One of interface-type resistive switching is considered to originate from the movements of oxygen vacancies near the electrode/oxide interface, showing also bipolar switching. However, there remains an essential issue that the interface-type switching in various perovskite oxides has not been investigated in detail. In this work, we have tried to increase oxygen vacancies in Metal Organic Decomposition (MOD)-made BaTiO3 (BT) thin film by nitrogen annealing especially near the interface, thereafter evaluated the effect on the endurance properties of BT thin film diode. Other than the merits of Chemical Solution Deposition (CSD) that large area and uniform deposition are available, the elements in MOD are mixed metalorganically at the molecular level and are chemically stable, so MOD is advantageous to obtain a homogeneous film. Resistive Random Access Memory (ReRAM) has so far been investigated with various types of oxide materials including ABO3 perovskite materials [1-3] such as BT [4,5]. However, little has been reported on BT thin films for ReRAM prepared by a CSD technique such as MOD. Furthermore, a mechanism of interface-type resistive switching is considered to originate from the movements of oxygen vacancies near the electrode/oxide interface, also showing the bipolar-type switching [6]. However, one of the important issues in ReRAM is that the mechanism of bipolar-type resistive switching is unclear still now when used perovskite oxides. It is considered that oxygen vacancies and electrons in the oxide play important roles in the bipolar-type resistive switching. In this work, we prepared BT thin films by the MOD process
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