In this study, the hopping conduction distance and bipolar switching properties of the Gd:SiOx thin film by (radio frequency, rf) rf sputtering technology for applications in RRAM devices were calculated and investigated. To discuss and verify the electrical switching mechanism in various different constant compliance currents, the typical current versus applied voltage (I-V) characteristics of gadolinium oxide RRAM devices was transferred and fitted. Finally, the transmission electrons’ switching behavior between the TiN bottom electrode and Pt top electrode in the initial metallic filament forming process of the gadolinium oxide thin film RRAM devices for low resistance state (LRS)/high resistance state (HRS) was described and explained in a simulated physical diagram model.

In the reset state, the decay reaction mechanism and bipolar switching properties of vanadium oxide thin film RRAM devices for LRS/HRS are investigated and discussed here. To discover the properties of I-V switching curves, the first order rate law behaviors of the reset state between the resistant variety properties and the reaction time were observed. To verify the decay reaction mechanism in the reset state, vanadium oxide thin films from RRAM devices were measured by different constant voltage sampling and exhibited the same decay reaction rate constant. Finally, the electrical conduction transfer mechanism and metallic filament forming model described by I-V switching properties of the RRAM devices were proven and investigated.

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.

Activation energy, bipolar resistance switching behavior, and the electrical conduction transport properties of ITO_X:SiO₂ thin film resistive random access memory (RRAM) devices were observed and discussed. The ITO_X:SiO₂ thin films were prepared using a co-sputtering deposition method on the TiN/Si substrate. For the RRAM device structure fabrication, an Al/ITO_X:SiO₂/TiN/Si structure was prepared by using aluminum for the top electrode and a TiN material for the bottom electrode. In addition, grain growth, defect reduction, and RRAM device performance of the ITO_X:SiO₂ thin film for the various oxygen gas flow conditions were observed and described. Based on the I-V curve measurements of the RRAM devices, the turn on-off ratio and the bipolar resistance switching properties of the Al/ITO_X:SiO₂/TiN/Si RRAM devices in the set and reset states were also obtained. At low operating voltages and high resistance values, the conductance mechanism exhibits hopping conduction mechanisms for set states. Moreover, at high operating voltages, the conductance mechanism behaves as an ohmic conduction current mechanism. Finally, the Al/ITO_X:SiO₂/TiN/Si RRAM devices demonstrated memory window properties, bipolar resistance switching behavior, and nonvolatile characteristics for next-generation nonvolatile memory applications.

In this work, lead-free (Na_0.475K_0.475Li_0.05)NbO₃ + x wt.% ZnO (NKLN, x = 0 to 0.3) piezoelectric ceramics with high piezoelectric g-coefficients were prepared by conventional solid-state synthesis method. By adding different concentrations of ZnO dopants, we aimed to improve the material properties and enhance their piezoelectric properties. The effects of the ZnO addition on the microstructure, dielectric, piezoelectric and ferroelectric properties of the proposed samples are investigated. Adding ZnO reduced the dielectric constant and improved the g-value of the samples. The properties of the samples without ZnO doping were g₃₃ = 31 mV·m/N, g₁₅ = 34 mV·m/N, k_p = 0.39, Q_m = 92, ε_r = 458, d₃₃ = 127 pC/N and dielectric loss = 3.4%. With the preferable ZnO doping of 1 wt.%, the piezoelectric properties improved to g₃₃ = 40 mV·m/N, g₁₅ = 44 mV·m/N, k_p = 0.44, Q_m = 89, ε_r = 406, d₃₃ = 139 pC/N and dielectric loss = 2.4%. Finally, ring-shaped shear mode piezoelectric accelerometers were fabricated using the optimum ZnO-doped samples. The simulated resonant frequency using ANSYS 2024 R1 software was approximately 23 kHz, while the actual measured resonant frequency of the devices was 19 kHz. The sensitivity was approximately 7.08 mV/g. This piezoelectric accelerometer suits applications requiring lower sensitivity and higher resonant frequencies, such as monitoring high-frequency vibrations in high-speed machinery, robotic arms or scientific research and engineering fields involving high-frequency vibration testing.