A set of (001) epitaxial NiO films were prepared on highly textured (001) Pt seed layers using magnetron sputtering, and their resistive switching performance was measured. Cube-to-cube epitaxial relationships of NiO(001)//Pt(001) and NiO[001]//Pt[001] were demonstrated. Currentvoltage measurements revealed that the Ag/(001)NiO/(001)Pt capacitor structures exhibited stable bipolar switching behavior with an ON/OFF ratio of 20 and an endurance of over 5 Â 10 3 cycles. Furthermore, inserting a HfO 2 buffer layer between the NiO film and the Ag top electrode increased the ON/OFF ratio to more than 10 3 and reduced the SET/RESET voltage to below 60.2 V. These enhancements are attributed to the differing filament growth mechanisms that occur in the NiO and HfO 2 layers. The present work suggests that Ag/HfO 2 /(001)NiO/(001)Pt capacitor structures are a promising technology for next-generation, ultra-low voltage resistive switching memory.

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：Amorphous Ge-doped HfO x films have been deposited on p-Si(100) substrates by means of RF magnetron sputtering. Microstructural investigations reveal the partial oxidation of doped Ge atoms in the amorphous HfO x matrix and the existence of HfSiO x interfacial layer. Capacitance-voltage hysteresis of the Ag/ Ge-doped HfO x /Si/Ag memory capacitor exhibits a memory window of 3.15 V which can maintain for more than 510 4 cycles. Current-voltage characteristics reveal that Poole-Frenkel tunneling is responsible for electron transport in the Ge-doped HfO x film.

Photo-induced changes of capacitance-voltage curves for amorphous Ni-doped HfO 2 films are probed under different visible light illumination conditions. The illumination-induced minority carriers injection effect enhances the negative shift of flat band voltage, and results in a significant enlargement of memory window. This enlargement exhibits negligible dependence on light wavelength but strong dependence on light intensity in the visible light region. A large memory window width of 6.12 V is obtained under illumination using 650 nm red light with an intensity of 5 mW cm −2 . Acceptable endurance and retention properties show potential applications on new-type photosensitive nano-floating-gate nonvolatile memory devices.