This work reports the effect of Ti diffusion on the bipolar resistive switching in Au/BiFeO₃/Pt/Ti capacitor-like structures. Polycrystalline BiFeO₃ thin films are deposited by pulsed laser deposition at different temperatures on Pt/Ti/SiO₂/Si substrates. From the energy filtered transmission electron microscopy and Rutherford backscattering spectrometry it is observed that Ti diffusion occurs if the deposition temperature is above 600°C. The current-voltage (I–V) curves indicate that resistive switching can only be achieved in Au/BiFeO₃/Pt/Ti capacitor-like structures where this Ti diffusion occurs. The effect of Ti diffusion is confirmed by the BiFeO₃ thin films deposited on Pt/sapphire and Pt/Ti/sapphire substrates. The resistive switching needs no electroforming process, and is incorporated with rectifying properties which is potentially useful to suppress the sneak current in a crossbar architecture. Those specific features open a promising alternative concept for nonvolatile memory devices as well as for other memristive devices like synapses in neuromorphic circuits.

43°Y-cut lithium niobate (LiNbO₃, LN) single-crystalline thin films, which are integrated with two types of Bragg reflectors of W/SiO₂ and Mo/SiO₂, respectively, are fabricated by means of the crystal-ion-slicing technique. Crack-free LN thin films are obtained when the Mo/SiO₂ reflector is adopted, while crumples take place when the LN thin film is combined with W/SiO₂. Moreover, solidly-mounted-type thin film bulk acoustic wave resonators (LN-SMRs) based on the single-crystalline LN film and Bragg reflector layers of Mo/SiO₂ are prepared and characterized. The results indicate that the LN thin film combined with the Mo/SiO₂ reflector has good thin film quality, and $k_{eff}^2$ of the LN-SMR reaches 20%.

This article investigates a spurious resonance appearing near the antiresonance when the double-busbar configuration is applied to layered surface acoustic wave (SAW) resonators using 42 $^\circ$ YX-LiTaO $_3$ thin plates, and possible mitigation methods are studied both theoretically and experimentally. First, the origin of the spurious resonance is revealed, and the influence of structural parameters is studied using the periodic 3-D finite-element method (FEM) powered by the hierarchical cascading technique (HCT). Then, possible methods are discussed for spurious mitigation. Finally, experimental data are provided for validation of the present analysis.

This paper reports an LNO surface acoustic wave (SAW) resonator based on a shear horizontal mode with high operating frequency over 3 GHz, large electromechanical coupling of 33.54%, Q factor of 380, and a relatively good figure of merit (FOM) of 127. Combing crystal-ion-slicing (CIS) technology with a room temperature bonding method, a 4-inch single crystalline LNO thin film on silicon is prepared successfully. The influence of damaged LNO film on crystalline quality and SAW performance is comprehensively analyzed. After totally removing the damaged layer, the electromechanical coupling and Q factor is significantly improved. The high-performance SAW resonator possesses the potential to meet the requirements of SAW filters for the fifth-generation (5G) communication in terms of high frequency, large bandwidth, and a high-quality factor.

A 43° rotated Y-cut LiNbO₃ (LN) single-crystal thin film coated with a bottom electrode and a Mo/Ti Bragg reflector is successfully transferred onto the 4-in. LN wafer substrate by means of crystal-ion-slicing (CIS) technique and benzocyclobutene bonding method. The multilayer film is crack-free, and the Mo/Ti reflector shows good acoustic reflection efficiency. A thin film bulk acoustic wave resonator based on the Mo/Ti Bragg reflector and the LN thin film (LN-BAW) is prepared, and the properties are further analyzed. The results indicate that the LN-BAW provides a large K_t² of ∼16.63% and the Q-factor and figure-of-merit of the LN-BAW reach 183 and 30.4, respectively.