We investigated the effect of top contact interface and microstructural characteristics of the insulating layers on resistive switching behaviors by fabricating and characterizing the HfO2/ZnO bilayer heterostructures. Different thickness of ZnO underlying layer and different deposition temperatures of the upper HfO2 layer were designed to analyze the intrinsic contribution of the crystalline microstructure of the insulating bilayer. Pt and Ti top electrodes were used to demonstrate the extrinsic contribution of the interface configuration. It was observed that all devices show bipolar RS characteristics. Unlike the device composed of Pt/HfO2/ZnO/Pt that exhibit an abrupt switching, a gradually continuous switching in the reset process was identified in the device composed of Ti/HfO2/ZnO/Pt. Interfacial charge migration process/characteristic plays a key role in the RS process as well as its conduction mechanism. The RS performance of the former is significantly better than that of the latter, including much lower reset voltage, two orders of magnitude larger OFF/ON ratio and HRS resistance. In addition, as compared to the intrinsic contribution arising from the microstructure of the HfO2/ZnO bilayer to the RS performances and current transport mechanism, the extrinsic effect contributed from the electrode characteristics (and its interface) is dominant.

It is relatively easy to obtain highly oriented/textured Ba(ZrxTi1–x)O3 (BZT) films by magnetron sputtering, but it is complicated to control the composition of these sputtered oriented films. Here, a series of BZT ceramic targets with different ingredients (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) and a BaTiO3 (x = 0) target were fabricated by solid-state sintering. Then, the corresponding BZT thin films were deposited on LaNiO3 (LNO) buffered Pt/Ti/(001)Si substrates adopting radio-frequency magnetron sputtering. Benefit from the prefabricated (001)-LNO buffer layer and optimized BZT film preparation process, all BZT films exhibit highly (00l) preferred orientation. However, the degree of orientation, lattice parameter, dielectric properties, ferroelectric behaviors, and energy-storage characteristics are all highly dependent on the Zr content of BZT films sputtered by targets with the same composition. (00l)-oriented BZT films with relatively low Zr content have a better crystalline structure [narrower full width at half maximum (FWHM), larger grains]. It is also found that the rising of the Zr content in (00l)-oriented BZT films will result in a larger out-of-plane lattice parameter, and these results indicate that the doping amount of Zr will strongly change the heterointerface stress/strain states and the growth mode of the oriented films, and then effectively tailor their electric performances.