Low-Intensity Light Detection with a High Detectivity Using 2D-Sb2Se3 Nanoflakes on 1D-ZnO Nanorods as Heterojunction Photodetectors.

Multifunctional photodetectors (PDs) with broadband responsivity (R) and specific detectivity (D*) at low light intensities are gaining significant attention. Thus, we report a bilayer PD creatively fabricated by layering two-dimensional (2D) Sb2Se3 nanoflakes (NFs) on one-dimensional (1D) ZnO nanorods (NRs) using simple thermal transfer and hydrothermal processes. The unique coupling of these two layers of materials in a nanostructured form, such as 2D-Sb2Se3 NFs/1D-ZnO NRs, provides an effective large surface area, robust charge transport paths, and light-trapping effects that enhance light harvesting. Furthermore, the combination of both layers can effectively facilitate photoactivity owing to proper band alignment. The as-fabricated device demonstrated superior overall performance in terms of a suitable bandwidth, good R, and high D* under low-intensity light, unlike the single-layered 1D-ZnO NRs and 2D-Sb2Se3 NF structures alone, which had poor detectivity or response in the measured spectral range. The PD demonstrated a spectral photoresponse ranging from ultraviolet (UV) to visible (220-628 nm) light at intensities as low as 0.15 mW·cm-2. The PD yielded a D* value of 3.15 × 1013 Jones (220 nm), which reached up to 5.95 × 1013 Jones in the visible light region (628 nm) at a 3 V bias. This study demonstrated that the 2D-Sb2Se3 NFs/1D-ZnO NRs PD has excellent potential for low-intensity light detection with a broad bandwidth, which is useful for signal communications and optoelectronic systems.

Photoilluminated Redox-Processed Rh2P Nanoparticles on Photocathodes for Stable Hydrogen Production in Acidic Environments.

While photoelectrochemical (PEC) cells show promise for solar-driven green hydrogen production, exploration of various light-absorbing multilayer coatings has yet to significantly enhance their hydrogen generation efficiency. Acidic conditions can enhance the hydrogen evolution reaction (HER) kinetics and reduce overpotential losses. However, prolonged acidic exposure deactivates noble metal electrocatalysts, hindering their long-term stability. Progress requires addressing catalyst degradation to enable stable, efficient, and acidic PEC cells. Here, we proposed a process design based on the photoilluminated redox deposition (PRoD) approach. We use this to grow crystalline Rh2P nanoparticles (NPs) with a size of 5-10 on 30 nm-thick TiO2, without annealing. Atomically precise reaction control was performed by using several cyclic voltammetry cycles coincident with light irradiation to create a system with optimal catalytic activity. The optimized photocathode, composed of Rh2P/TiO2/Al-ZnO/Cu2O/Sb-Cu2O/ITO, achieved an excellent photocurrent density of 8.2 mA cm-2 at 0 VRHE and a durable water-splitting reaction in a strong acidic solution. Specifically, the Rh2P-loaded photocathode exhibited a 5.3-fold enhancement in mass activity compared to that utilizing just a Rh catalyst. Furthermore, in situ scanning transmission electron microscopy (STEM) was performed to observe the real-time growth process of Rh2P NPs in a liquid cell.

Retraction: Progressive p-channel vertical transistors fabricated using electrodeposited copper oxide designed with grain boundary tunability.

Retraction of 'Progressive p-channel vertical transistors fabricated using electrodeposited copper oxide designed with grain boundary tunability' by Sung Hyeon Jung et al., Mater. Horiz., 2022, 9, 1010-1022, https://doi.org/10.1039/D1MH01568K.

Retraction: Ambipolar operation of progressively designed symmetric bidirectional transistors fabricated using single-channel vertical transistor and electrochemically prepared copper oxide.

Retraction of 'Ambipolar operation of progressively designed symmetric bidirectional transistors fabricated using single-channel vertical transistor and electrochemically prepared copper oxide' by Sung Hyeon Jung et al., Mater. Horiz., 2023, 10, 1373-1384, https://doi.org/10.1039/D2MH01413K.

Intensive harmonized synapses with amorphous Cu2O-based memristors using ultrafine Cu nanoparticle sublayers formed via atomically controlled electrochemical pulse deposition.

Resistive random-access memory (RRAM) devices have significant advantages for neuromorphic computing but have fatal problems of uncontrollability and abrupt resistive switching behaviors degrading their synaptic performance. In this paper, we propose the electrochemical design of an active Cu2O layer containing a strategic sublayer of ultrafine Cu nanoparticles (U-Cu NPs) to form uniformly dispersed conducting filaments, which can effectively improve the reliability for analog switching of RRAM-based neuromorphic computing. The electrochemical pulse deposited (EPD) U-Cu NPs are linked to the bottom electrode through a semi-conductive path within the bottom Cu2O layer, since the EPD is preferentially carried out on the conductive sites. All Cu2O films with U-Cu NPs are developed in situ in the single electrolyte bath without any pause. The proposed U-Cu NPs can concentrate the external electric field and can generate conductive filament paths for analog resistive switching. The applied electric field was uniformly spread to U-Cu NPs at the center of the active layer and displays resistive switching behavior via multiple conductive filaments. This shows a strong harmony between the resistance-switching characteristics and the analog operation of the active layer. This RRAM device shows outstanding gradual analog switching, great linearity, dynamic range, endurance, precision, speed, and retention characteristics simultaneously and adequately for neuromorphic computing by realizing multiple weak filament-type operation.

Surface-Confined Ultra-Low Scale Pd Engineered Layered Co(OH)2 toward High-Performance Hydrazine Electrooxidation in Alkaline Saline Water.

Applications of abundant seawater in electrochemical energy conversion are constrained due to the sluggish oxygen evolution reaction and the corrosive chlorine oxidation reaction. Hence, it is imperative to develop an efficient anodic reaction alternative suitable for coupling with the cathodic counterpart. Due to a low thermodynamic oxidation potential, hydrazine oxidation reaction (HzOR) offers a unique pathway to overcome these challenges. Herein, spontaneously in situ reduced atomic scale Pd surface-confined to electrochemically prepared layered Co(OH)2 on carbon cloth is synthesized. This study reveals the hydrazine and Pd-dependent morphological evolution of Co(OH)2 and its Pd hybrids into nanoparticulate form. Unlike various layered double hydroxides, Pd integrated Co(OH)2 benefits from the contribution of Co(OH)2 as an active HzOR catalyst and the reductive support to host Pd, resulting in synergistically improved performances. Mass activities of Pd in alkaline and alkaline saline electrolyte are 11.24 and 9.83 A mgPd -1 at 200 mV, respectively, corresponding to the highest HzOR activities among noble metals. The optimized Pd hybrid demonstrates ≈6.5 times the current density relative to PtC (14.91 mA cm-2 at 200 mV) in alkaline saline water with hydrazine. These findings would be beneficial to realize high overpotential anodic alternatives and reduce over-dependence on freshwater for electrocatalysis.

Ambipolar operation of progressively designed symmetric bidirectional transistors fabricated using single-channel vertical transistor and electrochemically prepared copper oxide.

In this study, a symmetric bidirectional transistors (SBT) is proposed. The device simultaneously implements the "strong-inversion" and "accumulation" mechanisms of a metal-oxide semiconductor field-effect transistor and TFT, respectively, in different bias directions in a single-channel vertical transistor (V-Tr). This ideal SBT device is designed and fabricated by selecting appropriate materials exhibiting a narrow bandgap and intrinsic characteristics of Sb-doped p-type Cu2O, using a V-Tr to optimize the device structure for high-field-induced short-channel and ambipolar operation, and implementing facile electrochemical deposition for channel and plasma channel treatments. To adopt artificial conductivity control for producing the transporting path of minority electron carriers, the patterned-channel-layer sidewall is locally treated using oxygen plasma, thereby suppressing the minority-carrier self-compensation. The SBT device exhibits an excellent on-current (i.e., symmetric accumulation and strong inversion modes in the p- and n-type channel regions, respectively) and excellent midregion off-current, similar to those of ideal ambipolar transistors. Moreover, owing to multilevel signals and excellent inverter behaviors, the SBT device is suitable for application in complementary-metal-oxide-semiconductors and logic memories.

Design of Bronze-Rich Dual-Phasic TiO2 Embedded Amorphous Carbon Nanocomposites Derived from Ti-Metal-Organic Frameworks for Improved Lithium-Ion Storage.

Dual-phasic (DP)-TiO2 -based composites are considered attractive anode materials for high lithium-ion storage because of the synergetic contribution from dual-phases in lithium-ion storage. However, a comprehensive investigation on more efficient architectures and platforms is necessary to develop lithium-storage devices with high-rate capability and long-term stability. Herein, for the first time, a rationally designed bronze-rich DP-TiO2 -embedded amorphous carbon nanoarchitecture, denoted as DP-TiO2 @C, from sacrificial Ti-metal-organic frameworks (Ti-MOFs) via a two-step pyrolysis process is proposed. The bronze/anatase DP-TiO2 @C nanocomposites are successfully synthesized using a unique pyrolysis process, which decomposes individually the metal clusters and organic linkers of Ti-MOFs. DP-TiO2 @C exhibits a significantly high density and even distribution of nanoparticles (<5 nm), enabling the formation of numerous heterointerfaces. Remarkably, the bronze-rich DP-TiO2 @C shows high specific capacities of 638 and 194 mAh g-1 at current densities of 0.1 and 5 A g-1 , respectively, owing to the contribution of the synergetic interfacial structure. In addition, reversible specific capacities are observed at a high rate (5 A g-1 ) during 6000 cycles. Thus, this study presents a new approach for the synthesis of DP-TiO2 @C nanocomposites from a sacrificial Ti-MOF and provides insights into the efficient control of the volume ratio in DP-TiO2 anode architecture.

Design of Functionally Stacked Channels of Oxide Thin-Film Transistors to Mimic Precise Ultralow-Light-Irradiated Synaptic Weight Modulation.

To utilize continuous ultralow intensity signals from oxide synaptic transistors as artificial synapses that mimic human visual perception, we propose strategic oxide channels that optimally utilize their advantageous functions by stacking two oxide semiconductors with different conductivities. The bottom amorphous indium-gallium-zinc oxide (a-IGZO) layer with a relatively low conductivity was designed for an extremely low initial postsynaptic current (PSCi) by achieving full depletion at a low negative gate voltage, and the stacked top amorphous indium-zinc oxide (a-IZO) layer improved the amplitude of the synaptic current and memory retention owing to the enhancement in the persistent photoconductivity characteristics. We demonstrated an excellent photonic synapse thin-film transistor (TFT) with a precise synaptic weight change even in the range of ultralow light intensity by adapting this stacking IGZO/IZO channel. The proposed device exhibited distinct ∆PSC values of 3.1 and 18.1 nA under ultralow ultraviolet light (350 nm, 50 ms) of 1.6 and 8.0 µW/cm2. In addition, while the lowest light input exhibited short-term plasticity characteristics similar to the "volatile-like" behavior of the human brain with a current recovery close to the initial value, the increase in light intensity caused long-term plasticity characteristics, thus achieving synaptic memory transition in the IGZO/IZO TFTs.

Progressive p-channel vertical transistors fabricated using electrodeposited copper oxide designed with grain boundary tunability.

A strategically designed electrodeposition method is proposed for the coating of p-type copper(i) oxide (Cu2O) channels for oxide thin film transistors. To date, conventional p-type oxide semiconductors have revealed a poor mobility and stability and this has obstructed the development of all oxide based logic devices. Furthermore, previous studies on p-type oxide transistors have been limited by the use of a typical planar type configuration. Our Cu2O electrodeposition method designed by incorporating Sb element promotes vertical alignment of the grain boundaries (GBs) and it perfectly coincides with the charge transport direction from the source to the drain in the vertical field effect transistors. These vertically aligned GBs are bundle type GBs and are likely to be ideal for vertical transistors with supreme electrical performances owing to the structurally suppressed grain boundary charge scattering. This alignment of the GBs in the electrodeposited Sb doped Cu2O (Sb:Cu2O) also demonstrates a superior vertical taper profile with conventional wet chemical etching owing to the extremely preferential etching rate along the GBs. Surprisingly, the sidewall formation, with a smooth and steep morphology causes the formation of abrupt and non-defective gate insulator/channel interfaces for superior spacer-free vertical transistors. Consequently, the Cu2O vertical field effect transistors exhibit extraordinary transistor performances of Vth = 0.4 V, µFE = 8 cm2 V-1 s-1, subthreshold swing = 0.24 V dec-1, on/off current ratio = 2 × 108 and qualified electrical and long-term stability characteristics under various environments. To the best of our knowledge, this is the first reported study on an electrodeposited method to design troublesome p-type oxide Cu2O as novel vertical transistors. Finally, power efficient logic inverter circuits with unprecedented performances, such as good noise margins, remarkable gain values of 15.6 (2 VDD) and 62.7 (5 VDD), and high frequency operation up to 10 kHz, are demonstrated using these p-type Cu2O transistors by interconnecting n-type IGZO transistors.

A synergistic strategy to remove hazardous water pollutants by mimicking burdock flower morphology structures of iron oxide phases.

Artificially mimicking structures/morphologies available in the nature to develop multifunctional materials for catalysis is receiving greater attention. Particularly, the burdock flower morphology, which has a hollow-globe surrounded by spiky sheets, represents a multifunctional structure helpful in adsorption as well as intercalation of molecules. Given this, we have strategically developed a robust microwave (MW) bubble-template process to achieve highly uniform α-Fe2O3 and carbon-enriched Fe3O4 (Fe3O4@C) phases resembling the characteristics of spiky hollow burdock morphologies. The utilization of the MW bubble-templates as a pretreatment to the iron-based precursor solution helps in producing hollowed open-space ferrous glycolate burdock flower morphology with rapid production rate and without any addition of extra agents. Such burdock flower structures remain intact even after annealing in air/N2 ambiance providing highly photoactive α-Fe2O3 or magnetic Fe3O4@C, respectively. Utilizing the hollow burdock flower structures together with the individual photo/magnetic properties of iron oxide phases, a dual-layer filter was designed to remove hazardous dye molecules from water, which efficiently photodegraded (99.2 %) in natural sunlight as well as showed excellent adsorption (99.7 %) within minutes. Comparatively, a lower catalytic activity using simple iron oxide nanoparticles, closed, and faded burdock morphologies were seen. Hence, the high catalytic activity in removing the dye molecules, retention of structural phases after repeated use, and strong durability were a result of the synergetic effect of photo/magnetic properties, activated surface/spiky open burdock structure.

Area-Selective Chemical Doping on Solution-Processed MoS2 Thin-Film for Multi-Valued Logic Gates.

Multi-valued logic gates are demonstrated on solution-processed molybdenum disulfide (MoS2) thin films. A simple chemical doping process is added to the conventional transistor fabrication procedure to locally increase the work function of MoS2 by decreasing sulfur vacancies. The resulting device exhibits pseudo-heterojunctions comprising as-processed MoS2 and chemically treated MoS2 (c-MoS2). The energy-band misalignment of MoS2 and c-MoS2 results in a sequential activation of the MoS2 and c-MoS2 channel areas under a gate voltage sweep, which generates a stable intermediate state for ternary operation. Current levels and turn-on voltages for each state can be tuned by modulating the device geometries, including the channel thickness and length. The optimized ternary transistors are incorporated to demonstrate various ternary logic gates, including the inverter, NMIN, and NMAX gates.

Energy Transfer-Induced Photoelectrochemical Improvement from Porous Zeolitic Imidazolate Framework-Decorated BiVO4 Photoelectrodes.

BiVO4 , which is a representative photoanode material for photoelectrochemical water splitting, intrinsically restricts high conversion efficiency, owing to faster recombination, low electron mobility, and short electron diffusion length. While the photocurrent density of typical BiVO4 corresponds to only 21.3% of the maximum photocurrent density (4.68 mA cm-2 ), decoration of the BiVO4 photoanode with zeolitic imidazolate framework-67 (ZIF-67) exhibits a synergetic effect to raise the overall photocatalytic ability at the BiVO4 surface region to a higher level via the energy-transfer process from BiVO4 to ZIF-67. The hybrid ZIF-67/BiVO4 photoanode follows two convenient photoelectrochemical pathways: 1) energy-transfer-induced water oxidation reaction in ZIF-67 and 2) water oxidation reaction by direct contact between the BiVO4 surface and electrolytes. Compared to the moderate photocurrent density (≈1 mA cm-2 ) of single-layer BiVO4 , the proposed ZIF-67/BiVO4 photoanodes show a remarkably high photocurrent (2.25 mA cm-2 ) with high stability, despite the lack of hole scavengers in the electrolyte. Furthermore, the absorbed photon-to-current efficiency of the ZIF-67/BiVO4 photoanode is ≈2.5 times greater than that of BiVO4 . This work proposes a promising solution for efficient water oxidation that overcomes the intrinsic material limitations of BiVO4 photoelectrodes by using energy transfer-induced photon recycling and the decoration of porous ZIFs.

ß-like FeOOH Nanoswords Activated by Ni Foam and Encapsulated by rGO toward High Current Densities, Durability, and Efficient Oxygen Evolution.

As an alternative to the oxygen evolution reaction (OER) electrocatalyst developed by a complex bi- or multimetal ion with layered double hydroxide (LDH) structures, we design a simple, self-supported, and single-metal-ion OER electrocatalyst having lower overpotentials and high current densities in alkaline water electrolyzers. Here, ß-like FeOOH nanosword structures encapsulated by reduced graphene oxide (rGO) were cost-effectively synthesized on formable Ni foam substrates as an efficient and highly durable OER catalyst. It is revealed that the rGO uniformly covered the ß-like FeOOH nanoswords to form a porous network achieving a lower overpotential of only 210 mV at 10 mA cm-2 with a stable operation for more than 40 h in alkali media. Moreover, a high current density of ∼300 mA cm-2 was achieved at less than 1.8 V. In-depth physical and electrochemical analysis indicated that the intrinsic charge transfer through activated Ni-foam, ß-like phase, and nanosword morphology was evidently beneficial for enhancing the OER activity of the bare FeOOH, and its encapsulation by rGO further improved the conductivity and long-life durability. Our integrated OER electrocatalyst developed by a simple method (repeated soaking and quenching process) will aid in scaling up ß-like FeOOH nanoswords for preparing uniform and large-area electrodes for industrial purposes.

Optimal n-Type Al-Doped ZnO Overlayers for Charge Transport Enhancement in p-Type Cu2O Photocathodes.

An effective strategy for improving the charge transport efficiency of p-type Cu2O photocathodes is the use of counter n-type semiconductors with a proper band alignment, preferably using Al-doped ZnO (AZO). Atomic layer deposition (ALD)-prepared AZO films show an increase in the built-in potential at the Cu2O/AZO interface as well as an excellent conformal coating with a thin thickness on irregular Cu2O. Considering the thin thickness of the AZO overlayers, it is expected that the composition of the Al and the layer stacking sequence in the ALD process will significantly influence the charge transport behavior and the photoelectrochemical (PEC) performance. We designed various stacking orders of AZO overlayers where the stacking layers consisted of Al2O3 (or Al) and ZnO using the atomically controlled ALD process. Al doping in ZnO results in a wide bandgap and does not degrade the absorption efficiency of Cu2O. The best PEC performance was obtained for the sample with an AZO overlayer containing conductive Al layers in the bottom and top regions. The Cu2O/AZO/TiO2/Pt photoelectrode with this overlayer exhibits an open circuit potential of 0.63 V and maintains a high cathodic photocurrent value of approximately -3.2 mA cm-2 at 0 VRHE for over 100 min.

High-Performance Non-Volatile InGaZnO Based Flash Memory Device Embedded with a Monolayer Au Nanoparticles.

Non-volatile memory (NVM) devices based on three-terminal thin-film transistors (TFTs) have gained extensive interest in memory applications due to their high retained characteristics, good scalability, and high charge storage capacity. Herein, we report a low-temperature (<100 °C) processed top-gate TFT-type NVM device using indium gallium zinc oxide (IGZO) semiconductor with monolayer gold nanoparticles (AuNPs) as a floating gate layer to obtain reliable memory operations. The proposed NVM device exhibits a high memory window (ΔVth) of 13.7 V when it sweeps from -20 V to +20 V back and forth. Additionally, the material characteristics of the monolayer AuNPs (floating gate layer) and IGZO film (semiconductor layer) are confirmed using transmission electronic microscopy (TEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) techniques. The memory operations in terms of endurance and retention are obtained, revealing highly stable endurance properties of the device up to 100 P/E cycles by applying pulses (±20 V, duration of 100 ms) and reliable retention time up to 104 s. The proposed NVM device, owing to the properties of large memory window, stable endurance, and high retention time, enables an excellent approach in futuristic non-volatile memory technology.

High-Intensity Ultrasound-Assisted Low-Temperature Formulation of Lanthanum Zirconium Oxide Nanodispersion for Thin-Film Transistors.

The process complexity, limited stability, and distinct synthesis and dispersion steps restrict the usage of multicomponent metal oxide nanodispersions in solution-processed electronics. Herein, sonochemistry is employed for the in situ synthesis and formulation of a colloidal nanodispersion of high-permittivity (κ) multicomponent lanthanum zirconium oxide (LZO: La2Zr2O7). The continuous propagation of intense ultrasound waves in the aqueous medium allows the generation of oxidant species which, on reaction, form nanofragments of crystalline LZO at ∼80 °C. Simultaneously, the presence of acidic byproducts in the vicinity promotes the formulation of a stable as-prepared LZO dispersion. The LZO thin film exhibits a κ of 16, and thin-film transistors (TFTs) based on LZO/indium gallium zinc oxide operate at low input voltages (≤4 V), with the maximum mobility (µ) and on/off ratio (Ion/Ioff) of 5.45 ± 0.06 cm2 V-1 s-1 and ∼105, respectively. TFTs based on the compound dielectric LZO/Al2O3 present a marginal reduction in leakage current, along with enhancement in µ (6.16 ± 0.04 cm2 V-1 s-1) and Ion/Ioff (∼105). Additionally, a 3 × 3 array of the proposed TFTs exhibits appreciable performance, with a µ of 3-6 cm2 V-1 s-1, a threshold voltage of -0.5 to 0.8 V, a subthreshold swing of 0.3-0.6 V dec-1, and an Ion/Ioff of 1-2.5 (×106).

Smart Bifunctional Sb2 Se3 Nanorods for Integrated Water Purification: Insoluble Liquid Separation and Photoelectrochemical Degradation.

Antimony selenide (Sb2 Se3 ) nanostructures enable bifunctional water purification by a single membrane through i) physical separation of water-insoluble oil and ii) photoelectrocatalytic degradation of water-soluble organic compounds. Sb2 Se3 nanorods with exposed surfaces of {h 0 0} and {h 0 l} planes exhibit superhydrophobicity (water contact angle of ≈159°) owing to extremely low surface energy of those dangling-bond-free van der Waals planes. Based on crystallographic understanding, superhydrophobic Sb2 Se3 nanorods were produced on a mesh-type substrate for utilization as a membrane for physical water/oil separation. Sb2 Se3 exhibited an optimal photocathodic response with p-type electrical conductivity under visible light along the longitudinal crystal direction. This indicated that the nanorods could be used as photoelectrocatalytic material for chemical water purification. A smart membrane with Sb2 Se3 nanostructures was proposed as a candidate for integrated water purification that can simultaneously accomplish water/oil separation and photoelectrocatalytic degradation of organic compounds in wastewater. Linear sweep voltammetry measurements of the Sb2 Se3 -membrane showed cathodic photocurrent generation (up to approximately 10 mA cm-2 at 0 V vs. reversible hydrogen electrode), which was enough to reduce O2 to an oxygen radical (O2 .- ) for degradation of methyl orange. Consequently, solar-driven integrated water purification was demonstrated for the first time by using a single material with a dual function of superhydrophobicity and photoactivity.

Bionanoelectronic platform with a lipid bilayer/CVD-grown MoS2 hybrid.

We demonstrate a bionanoelectronic platform for a supported lipid bilayer formed on an MoS2 film for biosensing, biomolecule recognition, and bioelectronic applications. A large-area MoS2 film was synthesized on a sapphire substrate and treated with O2 plasma or Al2O3 deposition to change the surface from hydrophobic to hydrophilic. Measurements of fluorescence and fluorescence recovery after photobleaching confirmed the physical properties of the lipid bilayer on the treated surfaces. We fabricated an electronic device using the treated MoS2 film and characterized the influence of the lipid bilayer on its electrical properties. Furthermore, transmembrane ion channels peptide (gramicidin A) were incorporated into the lipid bilayer and modulations of the electrical properties of the device under various pH conditions and calcium ion were observed. This sensitive and stable platform has strong potential for housing artificial channels and transmembrane ion channels for advanced bioapplications.

Highly Improved Quasi-Two-Dimensional Oxide Transistors via Non-centrosymmetric Nitrogen Dioxide Treatment, toward Extremely Low Process Temperature and Operant Self-Aligned Coplanar Structure.

Rapid degradations are typically encountered in low-temperature processed oxide thin-film transistors (TFTs) with a high indium composition and quasi-two-dimensional (Q2D) thin channel, owing to the breaking of numerous surface bonds of the Q2D oxide and the ineffectiveness of oxidation treatment. Strategically, a novel approach is proposed for the effective use of non-centrosymmetric nitrous oxide (NO2) as a reactive oxidizer gas for realizing the highly robust and rapid field-effect mobility properties of low-temperature-processed Q2D amorphous indium zinc oxide (a-IZO) TFTs. From the surface chemical analysis, it is found that NO2 stably reconstructs surface chemical bonding with NO3- ions by capturing the charged electrons and oxygen and the regions with and without NO2 treatment display extreme differences in their electrical conductivity. Thus, a new process design can be suggested for the fabrication of self-aligned coplanar Q2D transistors, with the aim of scaling down and replacing conventional hydrogen treatment or ultraviolet irradiation. This concept is tactically designed considering the problematic aging effect and impact of the NO2 treatment. The self-aligned coplanar top-gate Q2D a-IZO TFTs exhibit outstanding device performance with a field-effect mobility of 30.1 cm2 V-1 s-1 and a relatively low positive bias stress shift of 1.3 V at an extremely low process temperature of 80 °C.