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Herein, sol–gel-processed Y2O3 resistive random-access memory (RRAM) devices were fabricated. The top electrodes (TEs), such as Ag or Cu, affect the electrical characteristics of the Y2O3 RRAM devices. The oxidation process, mobile ion migration speed, and reduction process all impact the conductive filament formation of the indium–tin–oxide (ITO)/Y2O3/Ag and ITO/Y2O3/Cu RRAM devices. Between Ag and Cu, Cu can easily be oxidized due to its standard redox potential values. However, the conductive filament is easily formed using Ag TEs. After triggering the oxidation process, the formed Ag mobile metal ions can migrate faster inside Y2O3 active channel materials when compared to the formed Cu mobile metal ions. The fast migration inside the Y2O3 active channel materials successfully reduces the SET voltage and improves the number of programming–erasing cycles, i.e., endurance, which is one of the nonvolatile memory parameters. These results elucidate the importance of the electrochemical properties of TEs, providing a deeper understanding of how these factors influence the resistive switching characteristics of metal oxide-based atomic switches and conductive-metal-bridge-filament-based cells. [ABSTRACT FROM AUTHOR]

Herein, sol–gel-processed Y2O3–Al2O3 mixed oxide-based resistive random-access-memory (RRAM) devices with different proportions of the involved Y2O3 and Al2O3 precursors were fabricated on indium tin oxide/glass substrates. The corresponding structural, chemical, and electrical properties were investigated. The fabricated devices exhibited conventional bipolar RRAM characteristics without requiring a high-voltage forming process. With an increase in the percentage of Al2O3 precursor above 50 mol%, the crystallinity reduced, with the amorphous phase increasing owing to internal stress. Moreover, with increasing Al2O3 percentage, the lattice oxygen percentage increased and the oxygen vacancy percentage decreased. A 50% Y2O3–50% Al2O3 mixed oxide-based RRAM device exhibited the maximum high-resistance-state/low-resistance-state (HRS/LRS) ratio, as required for a large readout margin and array size. Additionally, this device demonstrated good endurance characteristics, maintaining stability for approximately 100 cycles with a high HRS/LRS ratio (>104). The HRS and LRS resistances were also retained up to 104 s without considerable degradation. [ABSTRACT FROM AUTHOR]

Yttrium oxide (Y2O3) resistive random-access memory (RRAM) devices were fabricated using the sol–gel process on indium tin oxide/glass substrates. These devices exhibited conventional bipolar RRAM characteristics without requiring a high-voltage forming process. The effect of current compliance on the Y2O3 RRAM devices was investigated, and the results revealed that the resistance values gradually decreased with increasing set current compliance values. By regulating these values, the formation of pure Ag conductive filament could be restricted. The dominant oxygen ion diffusion and migration within Y2O3 leads to the formation of oxygen vacancies and Ag metal-mixed conductive filaments between the two electrodes. The filament composition changes from pure Ag metal to Ag metal mixed with oxygen vacancies, which is crucial for realizing multilevel cell (MLC) switching. Consequently, intermediate resistance values were obtained, which were suitable for MLC switching. The fabricated Y2O3 RRAM devices could function as a MLC with a capacity of two bits in one cell, utilizing three low-resistance states and one common high-resistance state. The potential of the Y2O3 RRAM devices for neural networks was further explored through numerical simulations. Hardware neural networks based on the Y2O3 RRAM devices demonstrated effective digit image classification with a high accuracy rate of approximately 88%, comparable to the ideal software-based classification (~92%). This indicates that the proposed RRAM can be utilized as a memory component in practical neuromorphic systems. [ABSTRACT FROM AUTHOR]

In this study, we fabricated sol-gel-processed Y2O3-based resistive random-access memory (RRAM) devices. The fabricated Y2O3 RRAM devices exhibited conventional bipolar RRAM device characteristics and did not require the forming process. The long-term stability of the RRAM devices was investigated. The Y2O3 RRAM devices with a 20 nm thick Ag top electrode showed an increase in the low resistance state (LRS) and high resistance state (HRS) and a decrease in the HRS/LRS ratio after 30 days owing to oxidation and corrosion of the Ag electrodes. However, Y2O3 RRAM devices with inert Au-passivated Ag electrodes showed a constant RRAM device performance after 30 days. The 150 nm-thick Au passivation layer successfully suppressed the oxidation and corrosion of the Ag electrode by minimizing the chance of contact between water or oxygen molecules and Ag electrodes. The Au/Ag/Y2O3/ITO RRAM devices exhibited more than 300 switching cycles with a decent resistive window (>103). They maintained constant LRS and HRS resistances for up to 104 s, without significant degradation of nonvolatile memory properties for 30 days while stored in air. [ABSTRACT FROM AUTHOR]

We use sol–gel-processed SnO2 to fabricate thin-film transistors (TFTs) with good ambient stability, showing that SnO2 film densification can be effectively controlled by a choice of proper drying temperatures. In particular, TFTs comprising SnO2 films dried at 150 °C show conventional n-type semiconductor properties, high-saturation-regime field-effect mobility (7.3 cm2/Vs), good on/off current ratio, excellent sub-threshold swing values, and good electrical stability after 30-day exposure to ambient air, which alleviates the need for additional passivation layers to protect the active channel layer. Conversely, TFTs comprising SnO2 films dried at 50 or 100 °C show poor environmental stability due to low densification. Specifically, less dense films are characterized by the presence of loosely packed structures and small contact areas between crystallites, which promote the adsorption of gas molecules from the surroundings and result in significant TFT performance deterioration. [ABSTRACT FROM AUTHOR]

We demonstrate sol–gel-processed Mg-doped In2O3thin film transistors (TFTs) with high performance and improved stability. To improve the performance of indium oxide, which is unstable at a high negative threshold voltage, magnesium is used to suppress oxygen vacancy formation. As the Mg doping concentration increases, the oxygen deficiencies and OH impurities decrease, resulting in a positive shift in the threshold voltage and improved stability in negative bias stress environments. In this experiment, Mg-doped (0 to 2 wt%) indium oxide TFTs are fabricated. Indium oxide prepared from a synthesized solution of an indium nitrate hydrate precursor and 2-methoxyethanol has a mobility of 17.2 cm2/V s. In2O3TFTs doped with 1 wt% Mg also show a high mobility of 11.02 cm2/V s and a noticeable −1.5 V threshold voltage shift under negative bias stress. Our results suggest that the sol–gel-processed Mg-doped In2O3TFTs are a promising candidate for use in high-stability and high-performance applications in transparent devices. [ABSTRACT FROM AUTHOR]

In this letter, sol–gel-processed SnO2 films were deposited, with thicknesses varying from 3.5 to 5.0 nm, by controlling the concentration of the precursor solutions. Through electrical and spectroscopic investigations, it was found that the optical energy bandgap and the electron affinity were affected by the quantum confinement effect and Burstein–Moss effect. Moreover, the increased barrier height between Au and SnO2 semiconductors was enhanced when thinner SnO2 layers were used, resulting in strong Schottky diode characteristics. This letter allows one to examine the size scaling effects of ultrathin electrical devices with SnO2 channel layers. In addition, a generalized energy band diagram derived from the bandgap broadening in ultrathin SnO2 semiconductors is presented, which will allow the elucidation of the carrier transport mechanism and optical properties of quantum confined SnO2 semiconductor-based optical and electrical devices. [ABSTRACT FROM AUTHOR]

Sol–gel processed ultrathin nanostructured SnO2 thin-film transistors were successfully fabricated on a SiO2/Si substrate without using a self-aligned monolayer or high- ${k}$ insulator, which may be unsuitable techniques for the commercial fabrication of complementary metal–oxide–semiconductors. The highest extracted field mobility was approximately 100 cm2/V $\cdot$ s. In addition, by controlling the SnO2 film thickness, we successfully increased the on/off current ratio to ~107. The electrical performance of the proposed transistors is sufficient for high-resolution liquid crystal or organic light-emitting diode displays, which require a high field-effect mobility (>10 cm2/V $\cdot$ s) and high on/off current ratio (>106). Ultrathin SnO2 is also a promising rare-metal-free starting matrix for ternary and quaternary alloys, showing promising electric properties. [ABSTRACT FROM AUTHOR]

A sol-gel-processed ZrO2 layer was used as an active layer for a resistive random-access memory (RRAM). With top Ag electrodes, the fabricated devices show conventional bipolar switching memory properties. The impacts of device size and ZrO2 film thickness on device performance were investigated. The scaling of the device area and the successful increase in ZrO2 film thickness increased the high-resistance state (HRS)/low-resistance state (LRS) ratio values and improved the non-volatile memory properties, such as retention and endurance. The fabricated ITO/ZrO2/Ag RRAM shows good retention and endurance properties. The HRS and LRS were found to last for 104 s without any significant degradation. [ABSTRACT FROM AUTHOR]

Solution- p-type thin-film transistors, consisting of sol-gel-processed CuO films, were fabricated. The optoelectric properties of sol-gel-processed, CuO-based back gate thin-film transistors were investigated, and a detectivity of 1.38\times 10^ 11 (cm Hz ^ 1/2~\textW^-1) was achieved. This detectivity for sol-gel-processed CuO thin-film transistors is higher than that of the previously reported layered two-dimensional material systems and comparable to that of devices based on a one-dimensional nanowire system. Our results indicate that the sol-gel–processed, CuO-based photodetector system is a promising candidate for applications, such as near-infrared imaging devices, sensors, solar cells, and p-type inks for future printed electronics. [ABSTRACT FROM AUTHOR]

Sol–gel-processed Y2O3 films were used as active channel layers for resistive random access memory (RRAM) devices. The fabricated ITO/Y2O3/Ag RRAM devices exhibited the properties of conventional bipolar memory devices. A triethylamine stabilizer with a high vapor pressure and low surface tension was added to realize the local electric field area. During drying and high-temperature post-annealing processes, the large convective flow enhanced the surface elevation, and the increased –OH groups accelerated the hydrolysis reaction and aggregation. These phenomena afforded Y2O3 films with an uneven surface morphology and an increased surface roughness. The increased roughness of the Y2O3 films attributable to the triethylamine stabilizer enhanced the local electrical field, improved device reliability, and achieved successful repetition of the switching properties over an extended period. [ABSTRACT FROM AUTHOR]

Flexible indium tin oxide (ITO)/Y2O3/Ag resistive random access memory (RRAM) devices were successfully fabricated using a thermal-energy-free ultraviolet (UV)/ozone-assisted photochemical annealing process. Using the UV/ozone-assisted photochemical process, the organic residue can be eliminated, and thinner and smother Y2O3 films than those formed using other methods can be fabricated. The flexible UV/ozone-assisted photochemical annealing process-based ITO/Y2O3/Ag RRAM devices exhibited the properties of conventional bipolar RRAM without any forming process. Furthermore, the pure and amorphous-phase Y2O3 films formed via this process showed a decreased leakage current and an increased high-resistance status (HRS) compared with the films formed using other methods. Therefore, RRAM devices can be realized on plastic substrates using a thermal-energy-free UV/ozone-assisted photochemical annealing process. The fabricated devices exhibited a resistive window (ratio of HRS/low-resistance status (LRS)) of >104, with the HRS and LRS values remaining almost the same (i.e., limited deterioration occurred) for 104 s and up to 102 programming/erasing operation cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rare metal free SnO 2 main active layer was formed by a sol–gel process. • The Y 2 O 3 layers on SnO 2 semiconductors suitably function as passivation layers. • Partially diffused Y in SnO 2 can suppress the oxygen vacancy formation in SnO 2 semiconductor. • The fabricated SnO 2 TFTs with Y 2 O 3 passivation layers revealed remarkble NBS and PBS stability. Herein, a new combination of high-performance and bias-stress-stable SnO 2 thin-film transistors (TFTs) with Y 2 O 3 passivation layers is introduced. The Y 2 O 3 layers on SnO 2 semiconductors function suitably as passivation layers to minimize H 2 O adsorption and to avoid free carrier trapping by creating physical gaps that are larger than the characteristic diffusion length. Yttrium is observed to partially diffuse into SnO 2 , suppressing the formation of oxygen vacancies in the SnO 2 semiconductor because of its low electronegativity and standard electrode potential. The SnO 2 TFTs with Y 2 O 3 passivation layers exhibit a mobility of 5.7 ± 0.3 cm2/Vs, subthreshold swing of 1.1 ± 0.2 V/decade, threshold voltage (V TH) of + 6.8 ± 0.4 V, and on/off current ratio of 6.1 (±0.3) × 107. The fabricated sol–gel-processed SnO 2 TFTs with Y 2 O 3 passivation layers revealed remarkable negative and positive bias stress stabilities without hysteresis and consistently delivered high performance with enhancement mode operations. Owing to this high performance, the SnO 2 /Y 2 O 3 combination reported herein has potential as a commercial-product-level TFT for next-generation displays. [ABSTRACT FROM AUTHOR]

In this study, sol–gel-processed Li-doped SnO2-based thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The influence of Li dopant (wt%) on the structural, chemical, optical, and electrical characteristics was investigated. By adding 0.5 wt% Li dopant, the oxygen vacancy formation process was successfully suppressed. Its smaller ionic size and strong bonding strength made it possible for Li to work as an oxygen vacancy suppressor. The fabricated TFTs consisting of 0.5 wt% Li-doped SnO2 semiconductor films delivered the field-effect mobility in a 2.0 cm2/Vs saturation regime and Ion/Ioff value of 1 × 108 and showed enhancement mode operation. The decreased oxygen vacancy inside SnO2 TFTs with 0.5 wt% Li dopant improved the negative bias stability of TFTs. [ABSTRACT FROM AUTHOR]

Y-doped SnO2 thin film transistors were successfully fabricated by means of sol-gel process. The effect of Y concentration on the structural, chemical, and electrical properties of sol-gel-processed SnO2 films was investigated via GIXRD, SPM, and XPS; the corresponding electrical transport properties of the film were also evaluated. The dopant, Y, can successfully control the free carrier concentration by suppressing the formation of oxygen vacancy inside SnO2 semiconductors due to its lower electronegativity and SEP. With an increase of Ywt%, it was observed that the crystallinity and oxygen vacancy concentration decreased, and the operation mode of SnO2 thin film transistor changed from accumulation (normally on) to enhancement mode (normally off) with a positive Vth shift. [ABSTRACT FROM AUTHOR]

The effect of annealing ambient on SnO2 thin-film transistors (TFTs) fabricated via an ethanol-based sol-gel route was investigated. The annealing ambient has a significant effect on the structural characteristics and chemical composition and, in turn, the device performance. Although the crystalline-grain size of the SnO2 films annealed in air was the smallest, this size yielded the highest field-effect mobility. Compared with the minimization of boundary scattering via crystalline-size increase, augmentation of the free carrier concentration played a more critical role in the realization of high-performance devices. The fabricated SnO2 TFTs delivered a field-effect mobility, subthreshold swing, and on/off current ratio of 10.87 cm2/Vs, 0.87 V/decade, and 107, respectively. [ABSTRACT FROM AUTHOR]

We investigate the annealing environment effect on ZrO2-based resistive random-access memory (RRAM) devices. Fabricated devices exhibited conventional bipolar-switching memory properties. In particular, the vacuum-annealed ZrO2 films exhibited larger crystallinity and grain size, denser film, and a relatively small quantity of oxygen vacancies compared with the films annealed in air and N2. These led to a decrease in the leakage current and an increase in the resistance ratio of the high-resistance state (HRS)/low-resistance state (LRS) and successfully improved non-volatile memory properties, such as endurance and retention characteristics. The HRS and LRS values were found to last for 104 s without any significant degradation. [ABSTRACT FROM AUTHOR]

Abstract: A highly sensitive and stable tris(2,2′-bipyridyl)ruthenium(II) (Ru(bpy)3 2+) electrogenerated chemiluminescence (ECL) sensor was developed based on carbon nanotube (CNT) dispersed in mesoporous composite films of sol–gel titania and perfluorosulfonated ionomer (Nafion). Single-wall (SWCNT) and multi-wall carbon nanotubes (MWCNT) can be easily dispersed in the titania–Nafion composite solution. The hydrophobic CNT in the titania–Nafion composite films coated on a glassy carbon electrode certainly increased the amount of Ru(bpy)3 2+ immobilized in the ECL sensor by adsorption of Ru(bpy)3 2+ onto CNT surface, the electrocatalytic activity towards the oxidation of hydrophobic analytes, and the electronic conductivity of the composite films. Therefore, the present ECL sensor based on the CNT–titania–Nafion showed improved ECL sensitivity for tripropylamine (TPA) compared to the ECL sensors based on both titania–Nafion composite films without CNT and pure Nafion films. The present Ru(bpy)3 2+ ECL sensor based on the MWCNT–titania––Nafion composite gave a linear response (R 2 =0.999) for TPA concentration from 50nM to 1.0mM with a remarkable detection limit (S/N=3) of 10nM while the ECL sensors based on titania–Nafion composite without MWCNT, pure Nafion films, and MWCNT–Nafion composite gave a detection limit of 0.1μM, 1μM, and 50nM, respectively. The present ECL sensor showed outstanding long-term stability (no signal loss for 4 months). [Copyright &y& Elsevier]

Abstract: The sol–gel-immobilized Tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)3 2+] electrogenerated chemiluminescence (ECL) sensor was applied to the reversed-phase high-performance liquid chromatography (HPLC) determination of phenothiazine derivatives (promazine, chlorpromazine, triflupromazine, thioridazine, and trifluoperazine) and erythromycin in human urine samples. In this method, Ru(bpy)3 2+ was immobilized in sol–gel-derived titania (TiO2)–Nafion nanocomposite films coated on a dual platinum electrode. This method eliminates an extra pump needed for the delivery of Ru(bpy)3 2+ reagent into a reaction/observation zone in front of photomultiplier tube because the immobilized-Ru(bpy)3 2+ is recycled on the electrode surface by an applied potential at +1.3V versus Ag/AgCl (3M NaCl) reference electrode. The resulting analytical performances such as detection limit, working range, sensitivity, and measurement precision were slightly worse than those obtained with the conventional post-column Ru(bpy)3 2+ addition approach. The lack of significant interferences and the low detection limits for phenothiazine derivatives and erythromycin indicate that the proposed HPLC-Ru(bpy)3 2+ ECL detection method is suitable for the determination of those compounds in biological fluids. [Copyright &y& Elsevier]