%0 Journal Article
%A Zhang, Hehe
%A Yoo, Sijung
%A Menzel, Stephan
%A Funck, Carsten
%A Cüppers, Felix
%A Wouters, Dirk J.
%A Hwang, Cheol Seong
%A Waser, R.
%A Hoffmann-Eifert, Susanne
%T Understanding the Coexistence of Two Bipolar Resistive Switching Modes with Opposite Polarity in Pt/TiO 2 /Ti/Pt Nanosized ReRAM Devices
%J ACS applied materials & interfaces
%V 10
%N 35
%@ 1944-8252
%C Washington, DC
%I Soc.
%M FZJ-2018-05199
%P 29766 - 29778
%D 2018
%X Redox-type resistive random access memories based on transition-metal oxides are studied as adjustable two-terminal devices for integrated network applications beyond von Neumann computing. The prevailing, so-called, counter-eight-wise (c8w) polarity of the switching hysteresis in filamentary-type valence change mechanism devices originates from a temperature- and field-controlled drift-diffusion process of mobile ions, predominantly oxygen vacancies in the switching oxide. Recently, a bipolar resistive switching (BRS) process with opposite polarity, so-called, eight-wise (8w) switching, has been reported that, especially for TiO2 cells, is still not completely understood. Here, we report on nanosized (<0.01 μm2) asymmetric memristive cells from 3 to 6 nm thick TiO2 films by atomic layer deposition, which reveal a coexistence of c8w and 8w switching in the same cell. As important characteristics for the studied Pt/TiO2/Ti/Pt devices, the resistance states of both modes are nonvolatile and share one common state; i.e., the high-resistance state of the c8w mode equals the low-resistance state of the 8w-mode. A transition between the opposite hysteresis loops is possible by voltage control. Specifically, 8w BRS in the TiO2 cells is a self-limited low-energy nonvolatile switching process. Additionally, the 8w reset process enables the programming of multilevel high-resistance states. Combining the experimental results with data from simulation studies allows to propose a model, which explains 8w BRS by an oxygen transfer process across the Pt/TiO2 Schottky interface at the position of the c8w filament. Therefore, the coexistence of c8w and 8w BRS in the nanoscale asymmetric Pt/TiO2/Ti/Pt cells is understood from a competition between drift/diffusion of oxygen vacancies in the oxide layer and an oxygen exchange reaction across the Pt/TiO2 interface.
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:30088755
%U <Go to ISI:>//WOS:000444355700059
%R 10.1021/acsami.8b09068
%U https://juser.fz-juelich.de/record/851649