One-dimensional pure zinc oxide (ZnO) and Y-doped ZnO nanorod arrays have been successfully fabricated on the silicon substrate for comparison by a simple hydrothermal process at the low temperature of 90°C. The Y-doped nanorods exhibit the same c-axis-oriented wurtzite hexagonal structure as pure ZnO nanorods. Based on the results of photoluminescence, an enhancement of defect-induced green-yellow visible emission is observed for the Y-doped ZnO nanorods. The decrease of E₂(H) mode intensity and increase of E₁(LO) mode intensity examined by the Raman spectrum also indicate the increase of defects for the Y-doped ZnO nanorods. As compared to pure ZnO nanorods, Y-doped ZnO nanorods show a remarked increase of saturation magnetization. The combination of visible photoluminescence and ferromagnetism measurement results indicates the increase of oxygen defects due to the Y doping which plays a crucial role in the optical and magnetic performances of the ZnO nanorods.

Polycrystalline thin films of Ca-modified lead titanate (PCT) were deposited on Pt/SiO₂/Si substrates using a diol-based sol–gel process. Calcium acetylacetonate hydrate was adopted as a starting material instead of the calcium acetate or calcium nitrate tetrahydrate used conventionally. By changing the Ca content (5–35 mol%) and heating temperature (500–800°C), the influences of various processing parameters on the characteristics of thin films were studied. With the increase of the Ca content, the relative dielectric constant (ε _r) of PCT thin film increased from 43 to 70 at the heating temperature of 700°C. It was found that the coercive field (E _c) and the remanent polarization (P _r) decreased, but the pyroelectric coefficient (γ) increased with an increase of Ca content. The results reveal that PCT thin film with a Ca content of 25 mol% exhibits the largest figures of merit for the voltage responsivity and the specific detectivity at a heating temperature of 700°C.

Bi_0.8Pr_0.2Fe_0.95Mn_0.05O₃/Bi_3.96Gd_0.04Ti_2.95W_0.05O₁₂ (BPFMO/BGTWO) bilayer thin films with Multiferroic/Ferroelectric (MF/FE) structures were deposited onto Pt(111)/Ti/SiO₂/Si(100) substrates by using the sol-gel method with rapid thermal annealing. The BPFMO/BGTWO thin films exhibited well-saturated ferromagnetic and ferroelectric hysteresis loops because of the electro-magnetic coupling induced by the MF/FE structure. The remnant magnetization (2Mr) and remnant polarization (2Pr) were 4.6 emu/cm³ and 62 μC/cm², respectively. Moreover, the bipolar I-V switching curves of BPFMO/BGTWO bilayer thin films resistive random access memory (RRAM) devices were discussed, and investigated for LRS/HRS.

Copper-doped zinc oxide films (Zn_1−xCu_xO) (x = 0, 2%, 4%, 6%) were fabricated on conductive substrates using the sol-gel process. The crystal structure, optical and resistive switching properties of Zn_1−xCu_xO films are studied and discussed. RRAM is made using Zn_1−xCu_xO as the resistive layer. The results show that the (002) peak intensity and grain size of Zn_1−xCu_xOfilms increase from 0 to 6%. In addition, PL spectroscopy shows that the oxygen vacancy defect density of Zn_1−xCu_xO films also increases with the increase in Cu. The improved resistive switching performance of the RRAM device can be attributed to the formation of conductive filaments and the destruction of more oxygen vacancies in the Zn_1−xCu_xO film. Consequently, the RRAM device exhibits a higher low resistance state to high resistance state ratio and an HRS state of higher resistance value.

Bi_1-xMg_xFeO₃ (BMFO, x = 0, 0.02, 0.04, 0.06 and 0.08) multiferroic films were directly synthesized on flexible stainless steel (FSS), save the bottom electrode process, by means of sol–gel spin-coating technology. The effects of different bending conditions on ferroelectric, dielectric and leakage-current properties of BMFO films were investigated. The leakage-current densities of BiFeO₃ (BFO, x = 0) and BMFO (x = 0.06) films were 5.86 × 10⁻⁴ and 3.73 × 10⁻⁷ A/cm², which shows that the BMFO (x = 0.06) has more than three orders of magnitude lower than that of BFO film. The residual polarization (2 Pr) can be enhanced from 120 to 140 μC/cm². The proper doping of Mg in BiFeO₃ film could provide an effective method for reducing the leakage-current values as well as boosting the ferroelectric properties. In this study, the leakage-current mechanism of low electric field and high electric field of BMFO film is analyzed and established. In addition, the flexible BMFO film maintains practical ferroelectric and leakage-current properties at retention time of 10⁶ s under different symmetry bending conditions. These results indicate that the BFMO film will be very practical in opto-electronic and storage device applications.