Aluminum-doped zinc oxide (AZO) target was fabricated using AZO nanopowders synthesized by co-precipitation method and then the AZO films with different thicknesses were deposited on glass by d.c. magnetron sputtering at room temperature. AZO target is nodules free and shows homogeneous microstructure, ultra-high density and low resistivity. ZnAl₂O₄ phase appears in AZO target and disappears in AZO films. All AZO films show c-axis preferred orientation and hexagonal structure. With increasing film thickness from 153 to 1404 nm, the crystallinity was improved and the angle of (002) peak was close to 34.45°. The increase in grain size and surface roughness is due to the increase in film thickness. The decrease of resistivity is ascribed to the increases of carrier concentration and Hall mobility. The lowest resistivity is 9.6 × 10^-4 𝛺.cm. The average transmittance of AZO films exceeds 80%, and a sharp fundamental absorption edge with red-shifting is observed in the visible range. The bandgap decreases from 3.26 to 3.02 eV.

ZnMn₂O₄ active layer for resistance random access memory (RRAM) was deposited on p⁺-Si substrate by chemical solution deposition. The bipolar resistive switching behaviours of the Ag/ZnMn₂O₄/p⁺-Si capacitor are investigated. The bipolar resistive switching is reproducible and shows high ON/OFF ratio of > 10² and long retention times of > 10⁵ s. The conduction mechanism of the Ag/ZnMn₂O₄/p⁺-Si capacitor in the low-resistance state (LRS) is ohmic conduction, whereas that of the device in high-resistance state (HRS) successively undergoes Ohm’s law, trap-filled-limited and Child’s law conduction procedure at room temperature.

Mn$_{0.03}$Zn$_{0.97}$O (MZO)/amorphous La$_{0.7}Zn$_{0.3}$MnO$_3$ (LZMO) heterostructures were deposited on p$^+$-Si substratesthrough sol–gel spin coating. Ag/MZO/LZMO/p$^+$-Si and Ag/LZMO/MZO/p$^+$-Si devices exhibit a bipolar, reversibleand remarkable resistive switching behaviour at room temperature. The ratio of the resistance at high-resistance state (HRS)to that at low-resistance state (LRS) ($R_{\rm HRS}/R_{\rm LRS}$) in the Ag/LZMO/MZO/p$^+$-Si device is approximately five orders of magnitude, and is maintained after over 10$^3$ successive switching cycles or over a period of $2\times 10^6$ s, indicating good endurance property and retention characteristics. Conversely, the ratio in the Ag/MZO/LZMO/p$^+$-Si device began to decrease after 100 successive switching cycles. The LZMO/MZO interface could play an important role in the resistive switching behaviour of the devices. The dominant conduction mechanism of the two devices is charge-trap emission.