Imaging the Three-Dimensional Conductive Channel in Filamentary-Based Oxide Resistive Switching Memory

Filamentary-based oxide resistive memory is considered as a disruptive technology for nonvolatile data storage and reconfigurable logic. Currently accepted models explain the resistive switching in these devices through the presence/absence of a conductive filament (CF) that is described as a reversible nanosized valence-change in an oxide material. During device operation, the CF cycles billion of times at subnanosecond speed, using few tens of microamperes as operating current and thus determines the whole device’s performance. Despite its importance, the CF observation is hampered by the small filament size and its minimal compositional difference with the surrounding material. Here we show an experimental solution to this problem and provide the three-dimensional (3D) characterization of the CF in a scaled device. For this purpose we have recently developed a tomography technique which combines the high spatial resolution of scanning probe microscopy with subnanometer precision in material removal, leading to a true 3D-probing metrology concept. We locate and characterize in three-dimensions the nanometric volume of the conductive filament in state-of-the-art bipolar oxide-based devices. Our measurements demonstrate that the switching occurs through the formation of a single conductive filament. The filaments exhibit sizes below 10 nm and present a constriction near the oxygen-inert electrode. Finally, different atomic-size contacts are observed as a function of the programming current, providing evidence for the filament’s nature as a defects modulated quantum contact

Putative Adverse Outcome Pathway for CYP-induced developmental neurotoxicity.

<p>Brown boxes show molecular initiating events (MIE), key events (KEs) and adverse outcomes (AOs) related to cypermethrin exposure at the highest dose (20mg/kg; CYP20). Orange boxes show MIE, KEs and AOs related to cypermethrin exposure at the lower dose (5mg/kg; CYP5). Common mechanisms / commonly observed changes are in double-lined boxes.</p

Genes commonly dysregulated in the brain of CYP20 and CYP5-exposed offspring.

<p>Fold change ≥ 1.2.</p

Behavioral tests used in the two experiments.

<p>Control and CYP-exposed offspring were exposed to both weakly and highly emotionally challenging environments. Conditions were defined as weakly challenging when the animals could escape from the stress generated by the apparatus and luminosity was low (no more than 30 lux). On the contrary, conditions were defined as highly challenging when the animals were not able to escape from the stress generated by the apparatus and luminosity was high (200 lux). The orange circles show the conditions for the CYP5-exposed offspring while the brown circles show the conditions for the CYP20-exposed offspring.</p

General toxicity induced by perinatal exposure to cypermethrin.

<p><b>A</b>: Cypermethrin did not modify maternal weight gain during pre and postnatal exposure. Maternal weight gain was evaluated every two days, during the pre and postnatal period. <b>B</b>: Each treatment session was associated with a clinical and behavioral assessment of the mothers (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0184475#sec002" target="_blank">Materials and methods</a> for details). <b>C</b>: On the day of delivery, sex ratio within each group and the number of pups by litter were determined. Data are mean +/- sem; Experiment 1: n = 20-21/group; Experiment 2: n = 13-14/group. ** p < 0.01 and *** p < 0.001 compared to CTL.</p

Adult CYP5-exposed offspring displayed maladaptive behavior in response to highly stressful conditions.

<p><b>A</b>: The elevated plus maze (EPM) was used as a weakly challenging task. Total distance travelled in the apparatus (1–2), time spent and mean speed in different parts of the EPM were used to assess emotional reactivity (3). Time spent in stretched attend postures was also measured to collect data on risk assessment (4). <b>B</b>: Emotional reactivity in response to weakly challenging environments was also evaluated by confronting mice to a novel slightly lighted environment during 5 min: total distance travelled was monitored over the total duration of the test (1). Data were also analyzed on a minute-by minute basis (2). <b>C</b>: Emotional reactivity in response to highly challenging environments was evaluated in the forced swimming task by measuring total time spent immobile over the total duration of the test (1) and on a minute-by-minute basis (2). <b>D</b>: Habituation to a second exposure to stressful environments was assessed by confronting mice to the EPM 24h later the first trial. Distance travelled on day 2 is depicted on (1) and (2), and habituation between day 1 and day 2 is depicted on (3) and (4). (5) and (6) show how offspring habituate between day 1 and day 2 in terms of spatial exploration of the apparatus. Data are mean +/- sem; n = 13–14 / group. *p < 0.05, ** p < 0.01, *** p < 0.001.</p

Adult CYP5-exposed offspring displayed maladaptive behavior in response to social contexts.

<p><b>A</b>: In the three-chambered sociability test, CYP5-exposed offspring displayed no preference for the chamber containing the social partner (mouse 1), unlike the controls (1). When the object was replaced by a novel social partner (mouse 2) in a subsequent trial, CYP5-exposed offspring, as well as the controls, preferred interacting with the novel partner compared to the already known partner (2). * <i>p</i> < 0.05, ** <i>p</i> < 0.01, *** <i>p</i> < 0.001 compared to time spent in contact with wire cup containing mouse 1. <b>B</b>: Social skills were also assessed in more realistic conditions: in a territorial context <i>i</i>.<i>e</i>. a male—male interaction task and in a <b>C:</b> reproductive context <i>i</i>.<i>e</i>. male—female interaction task. In these tasks, both social and non-social behaviors were scored over the total duration of the test (1). The microstructure of social / non-social behaviors was also monitored (2). And each parameter was measured on a minute-by-minute basis (3). Data are mean +/- sem; n = 13–14 / group. *p < 0.05, ** p < 0.01, *** p < 0.001, # p < 0.09 compared to the controls.</p

Perinatal exposure to cypermethrin disturbed early postnatal development in male offspring.

<p><b>A</b>: Somatic growth and maturation endpoints revealed no significant effect of CYP. Body weight data are mean +/- sem; n = 20–21 /group in experiment 1 and n = 13–14 in experiment 2. Eyelid opening data are percent of pups with at least one eye opened. <b>B</b>: Neuromotor and reflex development investigate the state of motor development and its coordination, and its ability to maintain balance. CYP negatively impacted these parameters. Percentage of pups with the corresponding reflex. <b>C</b>: Communicative and auditory sensory functions in response to perinatal exposure to CYP. Communicative skills data are expressed in mean +/- sem; n = 20–21 /group in experiment 1 and n = 13–14 in experiment 2. Data related to auditory startle response are expressed as percent of pups having the reflex. *** p < 0.001, ** p < 0.01, *p < 0.05 and # p < 0.09.</p

Adult CYP20-exposed offspring displayed maladaptive behavior in response to highly stressful conditions.

<p><b>A</b>: The openfield was used as a weakly challenging task. Total distance travelled in the apparatus (1–2), time spent and the mean speed in different parts of the openfield were used to assess emotional reactivity (3). <b>B</b>: Emotional reactivity in response to highly challenging environments was evaluated by confronting mice to a novel cage with no sawdust. Total distance travelled was monitored over the total duration of the test (1). Data were also analyzed on a minute-by minute basis (2–3). <b>C-D</b>: Emotional reactivity in response to highly challenging environments was evaluated in the forced swimming task and the tail suspension task. In each condition, total time spent immobile was scored over the total duration of the test (1) and on a minute-by-minute basis (2). <b>E</b>: Habituation to a second exposure to stressful environments was assessed by confronting mice to the forced swimming task 24h later the first trial. Performance on day 2 is depicted on (1) and (2), and habituation between day 1 and day 2 is depicted on (3) and (4). Data are mean +/- sem; n = 20–21 /group. *** p < 0.001, ** p < 0.01, *p < 0.05 and # p < 0.09.</p

Morphological effects observed at the end of the treatment period (PND15).

<p>Morphological effects observed at the end of the treatment period (PND15).</p