Electron. Mater., Volume 2, Issue 1 (March 2021) – 4 articles

A solid solution of a 100Li₃PS₄·xLi₃PO₄ solid electrolyte was easily prepared by liquid-phase synthesis. Instead of the conventional solid-state synthesis methods, ethyl propionate was used as the reaction medium. The initial stage of the reaction among Li₂S, P₂S₅ and Li₃PO₄ was proved by ultraviolet-visible spectroscopy. The powder X-ray diffraction (XRD) results showed that the solid solution was formed up to x = 6. At x = 20, XRD peaks of Li₃PO₄ were detected in the prepared sample after heat treatment at 170 °C. However, the samples obtained at room temperature showed no evidence of Li₃PO₄ remaining for x = 20. Solid phosphorus-31 magic angle spinning nuclear magnetic resonance spectroscopy results proved the formation of a POS₃³⁻ unit in the sample with x = 6. Improvements of ionic conductivity at room temperature and activation energy were obtained with the formation of the solid solution. The sample with x = 6 exhibited a better stability against Li metal than that with x = 0. The all-solid-state half-cell employing the sample with x = 6 at the positive electrode exhibited a better charge–discharge capacity than that employing the sample with x = 0. Full article

A new organic material with three 4,4-difluoro-4-borata-3a-azonia-4a-aza-s-indacene dyes (BODIPYs) at the periphery of the central core is successfully synthesized (3BDP3T) and its corresponding aqueous nanoparticles are prepared via the encapsulation approach and characterized in detail both experimentally and theoretically with the aid of the Density Functional Theory (DFT). The linear and non-linear optical properties of the synthesized material are also studied. Until now, the development of organic materials with three BODIPYs as substituents is limited and their properties are not fully resolved. The obtained 3BDP3T-based nanoparticles exhibit far-red and near infrared (NIR) emission with photoluminescence quantum yields of 0.021, which is promising as a new fluorescent contrast agent in the far-red and NIR spectral regions. Full article

Modern technology asks for thin films of sustainable piezoelectrics, whereas electro-mechanical properties of such films are poorly explored and controlled. Here, dynamic and quasi-static polarization, dielectric, and piezoelectric responses were experimentally studied in thin-film stacks of barium titanate sandwiched between electrodes and grown on top of strontium titanate substrate. Accurate piezoelectric characterization was secured by using double beam interferometric technique. All out-of-plane responses were found to be hysteresis-free. Effective piezoelectric coefficient ~50 pm/V and linear strain-voltage characteristic were achieved. The observed behavior was ascribed to field induced out-of-plane polarization, whereas spontaneous polarization is in-plane due to in-plane tensile thermal strain. Hysteresis-free linear piezoresponse was anticipated in thin films on commercial silicon substrates, enabling large thermal strain. Full article

Co-sputtering of SiO₂ and high-κ Ta₂O₅ was used to make multicomponent gate dielectric stacks for In-Ga-Zn-O thin-film transistors (IGZO TFTs) under an overall low thermal budget (T = 150 °C). Characterization of the multicomponent layers and of the TFTs working characteristics (employing them) was performed in terms of static performance, reliability, and stability to understand the role of the incorporation of the high-κ material in the gate dielectric stack. It is shown that inherent disadvantages of the high-κ material, such as poorer interface properties and poor gate insulation, can be counterbalanced by inclusion of SiO₂ both mixed with Ta₂O₅ and as thin interfacial layers. A stack comprising a (Ta₂O₅)_x(SiO₂)_{100 − x} film with x = 69 and a thin SiO₂ film at the interface with IGZO resulted in the best performing TFTs, with field-effect mobility (µ_FE) ≈ 16 cm²·V⁻¹·s⁻¹, subthreshold slope (SS) ≈ 0.15 V/dec and on/off ratio exceeding 10⁷. Anomalous V_th shifts were observed during positive gate bias stress (PGBS), followed by very slow recoveries (time constant exceeding 8 × 10⁵ s), and analysis of the stress and recovery processes for the different gate dielectric stacks showed that the relevant mechanism is not dominated by the interfaces but seems to be related to the migration of charged species in the dielectric. The incorporation of additional SiO₂ layers into the gate dielectric stack is shown to effectively counterbalance this anomalous shift. This multilayered gate dielectric stack approach is in line with both the large area and the flexible electronics needs, yielding reliable devices with performance suitable for successful integration on new electronic applications. Full article