Effect of Pt top electrode deposition on the valence state and resistance switching behavior of NbO 2-x
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Effect of Pt top electrode deposition on the valence state and resistance switching behavior of NbO2‑x Jimin Lee1 · Jaeyeon Kim1 · Taeho Kim1 · Hyunchul Sohn1 Received: 8 April 2020 / Accepted: 12 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Resistive random-access memory (ReRAM) devices for cross-point array structures require selector elements to suppress the sneak current though neighboring cells. Niobium oxide is a promising candidate for one selector-one ReRAM (1S1R) device because of its diverse electrical characteristics such as resistance threshold switching in NbO2 and resistance memory switching in Nb2O5. In this study, a new method to fabricate a self-formed 1S1R device is suggested, which uses the top electrode Pt sputtering process. During the Pt sputtering of the top electrode, it was observed that the Nb4+ in NbO2-x layer was oxidized into N b5+, resulting in N b2O5-rich films. Such self-formed N b2O5/NbO2-x layer exhibits dissimilar resistance switching behaviors depending on the compliance current during memory operation. A switching model is proposed based on the resistance switching characteristics of the N b2O5/NbO2-x layer on the compliance current during memory operation.
1 Introduction Resistive random-access memory (ReRAM) operates based on resistive switching and is considered as next generation memory for crossbar array architecture. Among the resistive switching materials such as perovskite oxides [1], amorphous silicon [2], and multiferroic materials [3], binary metal oxides [4–6] are actively pursued because of their scalability, fast switching, and simple operation [7–11]. However, sneak current through neighboring cells must be suppressed for resistive switching to be applied in a crossbar array architecture [12]. To reduce sneak current, a selector device must be integrated into the memory device [13,14]. Various selector materials have been investigated such as NbO2 and V O2 which exhibit metal–insulator transitions (MIT) [15–17], chalcogenides with ovonic threshold switching [18–20], and solid electrolytes that act as mixed ionic electronic conductors [21,22]. MIT materials are good candidates for selector devices because of their bidirectional resistance threshold switching (TS) characteristics and thermal stability [16]. MIT materials undergo a transition from insulating state to a metallic state under critical conditions, e.g., temperature and electric * Hyunchul Sohn [email protected] 1
Department of Materials Science and Engineering, Yonsei University, Seoul 03722, Republic of Korea
field. NbO2 is an advantageous MIT material for circuit applications because of its high transition temperature [17]. TS occurs in crystalline N bO2, and the MIT transition is induced in the switching channel by Joule heating [23,24]. The required crystalline N bO2 switching channel can be created during forming or post annealing [16,25]. Due to the narrow compositional window in its equilibrium phase diagram, depositi
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