Effect of crystallographic anisotropy on the resistance switching phenomenon in perovskites
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Typical I-V curves of the three types of YBCO/Ag junctions. Upper left inset: Schematic drawing of the measurement. Bottom right inset: Typical time profile of the applied current.
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(Color online) Comparison of time scales for in-plane and out-of-plane diffusion processes. Initial LRS state represents an oxygen structure around 1 nm in size which is located at x = 0 (filled area); this state is not stable and undergoes the diffusion process. Dotted lines visualize snapshots of such process using one-dimensional diffusion equation for c(x,t) (see text) after 10, 100, and 1000 s in the out-of-plane direction (D c ) and dashed line after 10 s in the in-plane direction (D ab ) from the same initial state. Left inset: Schematic drawing of the YBCO/Ag junctions with contact made: a) only in the c-axis direction – type (i), b) only in the ab-plane direction – type (ii) and c) in both directions – type (iii). Right inset: Typical relaxation curve from LRS back to equilibrium HRS for a junction with a contact only in the c-axis direction. The typical relaxation time constant estimated from the exponential decay fit was about 9 h in qualitative agreement with our oxygen diffusion model. The measurements were done at 100 nA current and ∼1–10 mV voltage biases insufficient to cause any resistance switching. The relaxation times may, however, vary from sample to sample depending on the oxygen vacancy concentration, interface quality, and other factors.
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