Lithium manganese oxide (LiMn₂O₄) is an effective cathode material for high-capacity lithium-ion (Li-ion) batteries. Therefore, to optimize battery efficiency, it is essential to understand how sputtering deposition conditions affect the quality and performance of LiMn₂O₄. This research examines how argon deposition pressure affects the stoichiometric characteristics and electrochemical performance of LiMn₂O₄. The study finds that changing argon deposition pressures, from a low of 5 mTorr to a high of 30 mTorr, results in the formation of different coating stoichiometries. At low argon deposition pressures, stoichiometric LiMn₂O₄ cathode coatings formed, exhibiting the highest discharge capacity of 115 mAh/g. Conversely, at high argon deposition pressures, non-stoichiometric LiMn₂O₄ with lithium deficiency was produced. These coatings exhibited diminished electrochemical behavior, achieving a discharge capacity of only 70 mAh/g at 5 mTorr. The lack of lithium resulted in a significant reduction in electrochemical performance, indicated by a high surface charge transfer resistance (R₂ = 48,529 Ω), which led to a low discharge capacity of 40 mAh/g.

The authors report on a new table top radio frequency (RF)-magnetron sputtering unit and process for the sputter deposition of barium titanate thin films. Like silicon substrate in conventional electronics, strontium titanate (SrTiO3) is the substrate of choice in the emerging field of oxide electronics and hence Nb doped SrTiO3 n-type semiconducting substrates were considered. The authors observe substrate etching and nonstoichiometry in the film composition at high RF-power and low processing pressure, respectively. However, films deposited at 20 mTorr and 10 W of RF power resulted in stoichiometric BaTiO3. Layer by layer (two-dimensional) growth, prerequisite for epitaxial BaTiO3 on Nb:SrTiO3 (100) substrates, were realized at 600 °C. Hysteresis loops (phase angle versus applied voltage) in piezoresponse force microscopy confirm ferroelectricity of the films. Ultrathin epitaxial BaTiO3 on Nb:SrTiO3 (100) is of great interest as a ferroelectric tunnel junction with pronounced contrast between the ON/OFF tunnel resistance.

The electric stimulation (ES) of the cornea is a novel therapeutic approach to the treatment of degenerative visual diseases. Currently, ES is delivered by placing a mono-element electrode on the surface of the cornea that uniformly stimulates the eye along the electrode site. It has been reported that a certain degree of correlation exists between the location of the stimulated retinal area and the position of the electrode. Therefore, in this study, we present the development of a sectioned surface electrode for selective electric stimulation of the human cornea. The proposed device consists of 16 independent microelectrodes, a reference electrode, and 18 contact pads. The microelectrodes have a size of 200 µm × 200 µm, are arranged in a 4 × 4 matrix, and cover a total stimulation area of 16 mm². The proposed fabrication process, based on surface micromachining technology and flexible electronics, uses only three materials: polyimide, aluminum, and titanium, which allow us to obtain a simplified, ergonomic, and reproducible fabrication process. The fabricated prototype was validated to laboratory level by electrical and electrochemical tests, showing a relatively high electrical conductivity and average impedance from 712 kΩ to 1.4 MΩ at the clinically relevant frequency range (from 11 Hz to 30 Hz). Additionally, the biocompatibility of the electrode prototype was demonstrated by performing in vivo tests and by analyzing the polyimide films using Fourier transform infrared spectroscopy (FTIR). The resulting electrode prototype is robust, mechanically flexible, and biocompatible, with a high potential to be used for selective ES of the cornea.

The continued evolution of electronic devices relies on the development of new semiconductor memory technology. Given the high compatibility of the Hf0.5Zr0.5O2 thin films with the CMOS technology, we investigate the charge transport mechanisms that occur in a relative thick Hf0.5Zr0.5O2 thin film (4 to 6 nm-thick) when subjected to electrical stresses. To that end we fabricate Hf0.5Zr0.5O2 heterostructures with a Pt tip as the top electrode and TiN and Pt as bottom electrode by radio-frequency magnetron sputtering. After analyzing the surface morphology of the as-received and as-deposited films by atomic force microscopy, the transfer of the desired chemical stoichiometry from the sputtering target to the substrate surface is studied by Raman spectroscopy. The ferroelectricity of the Hf0.5Zr0.5O2 thin films is confirmed by piezoresponse force microscopy measurements, and a retention of 22 h is obtained, attesting to the non-volatility of the samples. Nano-scale electrical measurements reveal the presence of resistive switching, where the low resistance state (ON state) in both Pt-tip/Hf0.5Zr0.5O2/TiN and Pt-tip/Hf0.5Zr0.5O2/Pt heterostructures can be created by the formation of a conductive filament based on oxygen vacancies.