Mechanism for bipolar resistive switching in transition-metal oxides

We introduce a model that accounts for the bipolar resistive switching phenomenon observed in transition-metal oxides. It qualitatively describes the electric-field-enhanced migration of oxygen vacancies at the nanoscale. The numerical study of the model predicts that strong electric fields develop in the highly resistive dielectric-electrode interfaces leading to spatially inhomogeneous oxygen vacancies distribution and a concomitant resistive switching effect. The theoretical results qualitatively reproduce nontrivial resistance hysteresis experiments that we also report providing key validation to our model.

Figure 1

(Color online) (a) Schematic model with a single conductive channel within the dielectric. The three regions $L$, $R$, and $B$ correspond to the two high resistance interfaces and the more conductive central bulk, respectively. The small boxes indicate the domains. (b) Detailed scheme of the conductive path. The grayscale qualitatively depicts the variation in the oxygen vacancy concentration through the channel (darker corresponds to higher concentration). The top figure shows the initial state with uniformly distributed oxygen vacancies and the bottom one shows the inhomogeneous distribution after the first few “forming” voltage cycles (see text).

Figure 2

(Color online) Top panel: resistive hysteresis loop ($R_T$ vs $V$) for the subsequent voltage cycles number 5, 6, and 7. (a) Inset: the $R_T$ vs $I$ hysteresis (loop number 5) shows qualitatively similar results (the vertical axis scale is the same as in the main figure). Bottom panel: experimental hysteresis loops measured in (b) manganite and (c) cuprate devices. The first one was pulsed in current control mode while the second in voltage mode. The details of the experimental procedures are described in Refs. 21, 25, respectively.

Figure 3

(Color online) Density concentration profiles normalized to the initial uniform density value ${\delta }_i/{\delta }_o$ at the beginning of voltage cycles number 5, 6, and 7 in the symmetric system.

Figure 4

(Color online) Top (semi-log scale): snapshots of the density concentration profiles for the symmetric configuration normalized to the initial uniform density value ${\delta }_i/{\delta }_o$ during the hysteresis cycle (first half). Bottom: the corresponding profiles of local resistance ${\rho }_i$ for the same snapshots. Inset: position of the snapshots in the (first half) hysteresis loop.

Figure 5

(Color online) Resistive hysteresis loops obtained for an increasing degree of asymmetry. $A_L=1000$ and $A_R=1000$, 100, 50, and 25 in panels (a), (b), (c), and (d), respectively. The right panels show experimental data for a manganite (e) and a cuprate sample (f) that were rendered asymmetric by means of intense and fixed polarity pulsing. The former was pulsed in current control mode and the latter in voltage control similarly as in Refs. 21, 25, respectively. Notice the qualitative similarity of data of panels (e) and (f) with panel (d) and of data in Fig. 2b with panel (a). The data of Fig. 2c seem to be in between the results of panels (a) and (b).