I-V characteristics obtained for the pre-formed and post formed states of the oxide. The voltage sweeps form 0 to 9 V were applied twice on twenty different locations over the NiO layer of the blanket sample.
(Color online) Resistances of the pre-formed and post-formed states calculated over different locations on the NiO layer of the blanket sample. The resistive switch ratio R pre-forming/R post-forming is 108 Ω. The dispersion is small.
(Color online) Pre-forming (a) and post-forming (b) survey spectra obtained on the NiO/Pt stack before and after resistive switching by HAXPES. The NiO surface (hν = 2.1 keV) and bulk layer (hν = 6.5 keV and 9.75 keV) were successively probed. Spectra shifted on the y axis for convenience.
(Color online) STEM EDX image (top) and corresponding chemical analysis (bottom). The NiO composition is homogenous across the layer. A NiPt alloy is observed at the NiO/Pt interface.
(Color online) Ni 2p 3/2 (a), O 1s (b) core level and valence band photoelectron spectra (c) obtained by HAXPES at 2.1 keV. Bands shift toward high binding energies in the low resistive state (post-formed state) relatively to the Fermi level (E F), probably due to n-doping.
(Color online) (a) Platinum photoelectron spectra measured at 9.75 keV; (b) Plot of energy band shifts observed for the post-formed state as a function of photon beam energy. Peak shifts are similar for NiO core levels and their amplitude decrease from the surface to the buried interface. Regarding Platinum, no band shifts were observed in the low resistive state. The error bars are set at 0.15 eV.
(Color online) Top: oxygen core level photoelectron spectra compared for three different x-ray beam energies in pre-formed and post-formed states after background subtraction, normalization and energy shift correction.
(Color online) Top: nickel core level photoelectron spectra compared for three different x-ray beam energies in pre-formed and post-formed states after background subtraction, normalization and energy shift correction. Bottom: Gaussian/Lorentzian components used for spectra decomposition at 2.1 keV. The three high energy features are oxidized nickel (Ni2+ or Ni3+) contribution whereas, the low energy peak represents metallic nickel (Ni0) contribution.
Fit parameters of the peak around 851 eV, used for modeling the metallic nickel (Ni0) contribution in the two resistive states (cf. Fig. 8 ). Component full width at half-maximum (FWHM) and relative areas (with respect to total Ni 2p 3/2 signal area) are compared. Errors were estimated at about 0.08 eV for FWHM and 0.34% for relative areas.
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