In this study, the bipolar switching properties and electrical conduction behaviors of the ITO thin films RRAM devices were investigated. For the transparent RRAM devices structure, indium tin oxide thin films were deposited by using the RF magnetron sputtering method on the ITO/glass substrate. For the ITO/ITO_X/ITO/glass (MIM) structure, an indium tin oxide thin film top electrode was prepared to form the transparent RRAM devices. From the experimental results, the 10² On/Off memory ratio and bipolar switching cycling properties for set/reset stable states were found and discussed. All transparent RRAM devices exhibited the obvious memory window and low set voltage for the switching times of 120 cycles. The electrical transport mechanisms were dominated by the ohmic contact and space charge limit conduction (SCLC) models for set and reset states. Finally, the transmittances properties of the transparent ITO/ITO_X/ITO RRAM devices for the different oxygen growth procedures were about 90% according to the UV–Vis spectrophotometer for the visible wavelength range.

By the conventional solid state reaction method, a small amount of lithium fluoride (LiF) was used as the sintering promoter to improve the sintering and piezoelectric characteristics of (Ba_0.95Ca_0.05)(Ti_0.93Sn_0.07)O₃ (BCTS) lead-free piezoceramic sheets. Using X-ray diffraction (XRD) and a scanning electron microscope (SEM), the inferences of the crystalline and surface microstructures were obtained and analyzed. Then, the impedance analyzer and d₃₃-meter were used to measure the dielectric and piezoelectric characteristics. In this study, the optimum sintering temperature of the BCTS sheets decreased from 1450 °C to 1390 °C due to LiF doping. For the 0.07 wt % LiF-doped BCTS sheets sintered at 1390 °C, the piezoelectric constant (d₃₃) is 413 pC/N, the electric–mechanical coupling coefficient (k_p) is 47.5%, the dielectric loss (tan δ) is 3.9%, and the dielectric constant (ε_r) is 8100, which are all close to or even better than that of the pure undoped BCTS ceramics. The Curie temperature also improved, from 85 °C for pure BCTS to 140 °C for BCTS–0.07 LiF sheets. Furthermore, by using the vibration system and fixing 1.5 g tip mass at the end of the sheets, as the vibration frequency is 20 Hz, the proposed piezoelectric ceramic sheets also reveal a good energy harvesting performance at the maximum output peak voltage of 4.6 V, which is large enough and can be applied in modern low-power electronic products.

Using two kinds of targets (gallium and silicon dioxide) and the rf magnetron sputtering deposited technique, GdO_x:SiO₂ thin film RRAM devices were deposited on TiN/Si substrate to form a metal–insulator–metal (MIM) structure. In addition, different oxygen concentrations and rf sputtering power parameters were prepared for the GdO_x:SiO₂ thin films. Decrease of the defects and oxygen vacancies of the GdO_x:SiO₂ thin films were used and repaired by rapid thermal annealing technology. Indium tin oxide (ITO) as the top electrode on the GdO_x:SiO₂ thin film was prepared by the physical vapor deposition (PVD) method, and ITO/GdO_x:SiO₂/TiN/Si structures of the GdO_x:SiO₂ thin films’ RRAM devices were also made. In addition, the current–voltage curves and devices’ endurance properties were measured by an impedance analyzer. Finally, the crystalline style, the preferred phase, the grain size, and surface microstructure of the thin films were analyzed and observed from X-ray diffraction and field emission scanning electron microscope measurements.

In this study, non-stoichiometry lead-free piezoelectric ceramic Li_0.058(K_0.48Na_0.535)_0.966(Nb_0.9Ta_0.1)O₃ (LKNNT) thick films were deposited on Pt/Ti/Si substrates using spin-coating method technology to form a LKNNT/Pt/Ti/Si structure of the micro-pressure thick films. Additionally, the influence on the crystalline properties, surface microstructure images, and mechanical properties, and the piezoelectric properties of the non-stoichiometry lead-free piezoelectric ceramic Li_0.058(K_0.48Na_0.535)_0.966(Nb_0.9Ta_0.1)O₃ (LKNNT) thick films were observed, analyzed, and calculated using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), focused ion beam (FIB) microscopy, nano-indention technology, and other instruments. This study was divided into two parts: The first part was the investigation into the fabrication parameters and properties of the bottom layer (Pt) and buffer layer (Ti). The Pt/Ti/Si structures were achieved by the DC sputtering method, and then the rapid thermal annealing (RTA) post-treatment process was used to re-arrange the grains and reduce defects in the lead-free Li_0.058(K_0.48Na_0.535)_0.966(Nb_0.9Ta_0.1)O₃ (LKNNT) thick films. In the second part, lead-free Li_0.058(K_0.48Na_0.535)_0.966(Nb_0.9Ta_0.1)O₃ (LKNNT) powder was prepared by the solid-state reaction method, and then acetic acid (C₂H₄O₂) solvent was added to form a slurry for spin-coating technology processing. The fabrication parameters, thick film micro-structure, crystalline properties, nano-indention technology, and the piezoelectric coefficient characteristics of the developed lead-free Li_0.058(K_0.48Na_0.535)_0.966(Nb_0.9Ta_0.1)O₃ (LKNNT)/Pt/Ti/Si structure of the micro-pressure thick film devices a were investigated. According to the experimental results, the optimal fabrication processing parameters of the lead-free Li_0.058(K_0.48Na_0.535)_0.966(Nb_0.9Ta_0.1)O₃ (LKNNT) were an RTA temperature of 500 °C, a Ti buffer-layer thickness of 273.9 nm, a Pt bottom electrode-layer thickness of 376.6 nm, a theoretical density of LKNNT of 4.789 g/cm³, a lattice constant of 3.968 × 10⁻⁸ cm, and a d₃₃ value of 150 pm/V. Finally, regarding the mechanical properties of the micro-pressure devices for when a microforce of 3 mN was applied, the thick film revealed a hardness of 60 MPa, a Young’s modulus of 13 GPa, and an elasticity interval of 1.25 μm, which are suitable for future applications of micro-pressure devices.