A low temperature solution-processed thin-film transistor (TFT) using zinc oxide (ZnO) film as an exposed sensing semiconductor channel was fabricated to detect and identify various solution solvents. The TFT devices would offer applications for low-cost, rapid and highly compatible water-soluble detection and could replace conventional silicon field effect transistors (FETs) as bio-sensors. In this work, we demonstrate the utility of the TFT ZnO channel to sense various liquids, such as polar solvents (ethanol), non-polar solvents (toluene) and deionized (DI) water, which were dropped and adsorbed onto the channel. It is discussed how different dielectric constants of polar/non-polar solvents and DI water were associated with various charge transport properties, demonstrating the main detection mechanisms of the thin-film transistor.

In this work, we used a sol–gel process to fabricate a ZnO-ZrO ₂ -stacked resistive switching random access memory (ReRAM) device and investigated its switching mechanism. The Gibbs free energy in ZnO, which is higher than that in ZrO ₂ , facilitates the oxidation and reduction reactions of filaments in the ZnO layer. The current–voltage ( I – V ) characteristics of the device revealed a forming-free operation because of nonlattice oxygen in the oxide layer. In addition, the device can operate under bipolar or unipolar conditions with a reset voltage of 0 to ±2 V, indicating that in this device, Joule heating dominates at reset and the electric field dominates in the set process. Furthermore, the characteristics reveal why the fabricated device exhibits a greater discrete distribution phenomenon for the set voltage than for the reset voltage. These results will enable the fabrication of future ReRAM devices with double-layer oxide structures with improved characteristics.

A new sol-gel-derived Ti_xZr_ySi_zO nanocrystal (NC) memory with a high-performance data retention characteristic is demonstrated by the hot-hole-trapping method. Prior to rapid thermal annealing, the high-density NC layer is formed by depositing a well-mixed solution of titanium tetrachloride, silicon tetrachloride, and zirconium tetrachloride. The electrical properties of the sol-gel-derived NC memory are demonstrated in terms of memory window, charge retention, program speed, and endurance. The memory window of the NC memory from the novel hot-hole-trapping mechanism can be achieved up to 4.18 ± 0.21 V, and long retention times obtained from extrapolation up to 10⁶ s are observed as 8%, 13%, and 21% window narrowing under respective temperatures of 25 °C, 85 °C, and 125 °C. The good electrical performance is attributed to the contribution of the high density of isolated NCs and hole-trapped into the deep-trap energy level, so no significant lateral and vertical charge leakage occurs.

This study investigates an advanced copper (Cu) chemical displacement technique (CDT) with varying the chemical displacement time for fabricating Cu/SiO2-stacked resistive random-access memory (ReRAM). Compared with other Cu deposition methods, this CDT easily controls the interface of the Cu-insulator, the switching layer thickness, and the immunity of the Cu etching process, assisting the 1-transistor-1-ReRAM (1T-1R) structure and system-on-chip integration. The modulated shape of the Cu-SiO2 interface and the thickness of the SiO2 layer obtained by CDT-based Cu deposition on SiO2 were confirmed by scanning electron microscopy and atomic force microscopy. The CDT-fabricated Cu/SiO2-stacked ReRAM exhibited lower operation voltages and more stable data retention characteristics than the control Cu/SiO2-stacked sample. As the Cu CDT processing time increased, the forming and set voltages of the CDT-fabricated Cu/SiO2-stacked ReRAM decreased. Conversely, decreasing the processing time reduced the on-state current and reset voltage while increasing the endurance switching cycle time. Therefore, the switching characteristics were easily modulated by Cu CDT, yielding a high performance electrochemical metallization (ECM)-type ReRAM.

Direct ink-jet printing of a zinc-oxide-based thin-film transistor (ZnO-based TFT) with a three-dimensional (3-D) channel structure was demonstrated for ultraviolet light (UV) and visible light photodetection. Here, we demonstrated the channel structures by which temperature-induced Marangoni flow can be used to narrow the channel width from 318.9 ± 44.1 μm to 180.1 ± 13.9 μm via a temperature gradient. Furthermore, a simple and efficient oxygen plasma treatment was used to enhance the electrical characteristics of switching I_ON/I_OFF ratio of approximately 10⁵. Therefore, the stable and excellent gate bias-controlled photo-transistors were fabricated and characterized in detail for ultraviolet (UV) and visible light sensing. The photodetector exhibited a superior photoresponse with a significant increase of more than 2 orders of magnitude larger drain current generated upon UV illumination. The results could be useful for the development of UV photodetectors by the direct-patterning ink-jet printing technique. Additionally, we also have successfully demonstrated that a metal-semiconductor junction structure that enables plasmon energy detection by using the plasmonic effects is an efficient conversion of plasmon energy to an electrical signal. The device showed a significant variations negative shift of threshold voltage under different light power density with exposure of visible light. With the ZnO-based TFTs, only ultraviolet light detection extends to the visible light wavelength.

Electrochemical-metallization-type resistive random access memories (ReRAMs) show promising performance as next-generation nonvolatile memory. In this paper, the Cu chemical displacement technique (CDT) is used to form the bottom electrode of ReRAM devices. Compared with conventional deposition methods, the Cu-CDT method has numerous advantages for ReRAM fabrication, including low cost, low temperature fabrication, and the provision of unconsolidated Cu film and large surface roughness. Moreover, the Cu-CDT method is a favorable candidate for overcoming the Cu etching problem and is thus suitable for fabricating ReRAM devices. Using this technique, the surface morphology of a thin Cu film can be easily controlled. The obtained results show that the electric fields during the Forming and SET operations decreased, and the on-state current increased in the RESET operation, as the Cu-CDT displacement time was increased. The Cu-CDT samples exhibited a low operation field, large memory window (>10⁶), and excellent endurance switching cycle characteristics. Moreover, this paper proposes a model to explain the electrical characteristics of ReRAM, which are dependent on the surface morphology.