Fig. 7
Disorder analysis from switching traces. To investigate the variability of the switching current profiles, we performed K-means analysis with 12 clusters, restricting the data to the switching current traces in the positive voltage window. The result of the K-means analysis is shown in the cluster label map in a, and the mean response of each cluster in b. Note that clusters with <20 members are not plotted on this graph. To obtain a more quantitative estimate on the disorder, a Gaussian fitting procedure was applied to each switching current profile. An example of the data is shown in Fig. 5. c after conversion from voltage to time axis. The procedure involves finding the time at which the integral of the area under the curve is half of the total area under the curve, and fitting to only points at and beyond this time. Such points are indicated as red filled circles in the graph. A Gaussian fit is then performed on these points, with the constraint that the area of the Gaussian be equal to the area of the whole switching curve (to normalize for the polarization). The extracted map of the variance is plotted in d, and clearly shows substantial variability from one nanocapacitor to another
