The detailed microstructures of the Co3O4 nanosheets were characterized with TEM. Figure 1b represents typical TEM images of Co3O4 nanosheets. The HRTEM

image shown in the inset of Figure 1b clearly demonstrates lattice fringes with a d-spacing of 0.46 nm (111), matching well with the XRD pattern. To further elucidate find more the composition, energy-dispersive X-ray spectroscopy was used to determine the nominal stoichiometric atomic ratio of Co and O, as shown in Figure 1c. The chemical composition of the film was investigated by XPS analysis. The spectra (Co 2p and O 1s, as shown in Figure 2) were acquired and processed using standard XPS peak fitting. Two peaks at binding energies of 780 and 795.1 eV were observed from the Co 2p spectra. The tetrahedral Co2+ and octahedral Co3+ contributed to the spin-orbit doublet 2p spectral profile of Co3O4[21]. The relatively sharp peak widths correspond to 2p 1/2 to 2p 3/2 with separation of 15.1 eV, and the weak satellite structure found in the high binding energy side of 2p 3/2 and 2p l/2 transitions

indicate the co-existence of Co(II) and Co(III) on the surface of the material. The Co 2p spectrum is well consistent with the XPS spectrum of Co3O4[22–24]. Figure 2 Co 2 p (a) and O 1 s (b) XPS spectra of Co 3 O 4 sample. The O 1s spectra of the sample was also presented in the inset of the same figure The peak at around 530 eV is due to lattice O, while the peak at about 531.6 eV can be attributed to the low coordinated oxygen ions (chemisorbed oxygen) at the surface [25]. Figure LY2835219 solubility dmso 3a presents the typical current–voltage (I-V) characteristics of RRAM cell with the Au/Co3O4/ITO

structure, measured by sweeping voltage, at a speed of 1 V/s, in the sequence of 0 → 2 → 0 → −2 → 0 V. During the measurements, the bias voltages were applied to the gold top electrode with ITO bottom electrode about as ground. By steady increase of the positive voltages imposed on the RRAM cell, a pronounced change of resistance from the high-resistance state (HRS/OFF) to the low-resistance state (LRS/ON) was observed at about 1.05 V, which is called as the SET’ process, and then the device was set in threshold switching mode (no change in current after this voltage). Figure 3 RS properties of the Au/Co 3 O 4 /ITO memory cells. (a) Typical bipolar resistance switching I-V curves of the Au/Co3O4/ITO cells. (b) Electrical pulse-induced resistance switching of the Au/Co3O4/ITO memory cell at room temperature for 60 s, (inset, data retention of Au/Co3O4/ITO memory cell for >104 s), and (c) I-V curves on log scale. Subsequently, an opposite ‘RESET’ process could also be cited, with the voltage sweep to negative values check details bringing the device first to an intermediate switching state at −1.53 V that increased up to −1.93 V and, after that, completely to OFF state. The sample exhibits a typical bipolar nature of resistive switching.