Koehl, A.; Wasmund, H.; Herpers, A.; Guttmann, P.; Werner, S.; Henzler, K.; Du, H.; Mayer, J.; Waser, R.; Dittmann, R.: Evidence for multifilamentary valence changes in resistive switching SrTiO3 devices detected by transmission X-ray microscopy. APL Materials 1 (2013), p. 042102/1-8
10.1063/1.4822438

Abstract:
Transmission X-ray microscopy is employed to detect nanoscale valence changes in resistive switching SrTiO3 thin film devices. By recording Ti L-edge spectra of samples in different resistive states, we could show that some spots with slightly distorted structure and a small reduction to Ti3+ are already present in the virgin films. In the ON-state, these spots are further reduced to Ti3+ to different degrees while the remaining film persists in the Ti4+ configuration. These observations are consistent with a self-accelerating reduction within pre-reduced extended growth defects.