Boosting the adsorption capacity/selectivity of graphene oxide membranes via photocatalytic perforation for water treatment

Floating-gate (FG) synaptic transistors based on two-dimensional (2D) materials hold great promise for highly integrated neuromorphic computing hardware. Achieving an ultrathin tunnel oxide layer with high electrical and interface quality is crucial for the performance and reliability of 2D FG transistors but has been proven challenging. Here, we report that a high-quality FG stack, with an ultrathin tunneling layer HfOx and atomically abrupt FG interface, can be prepared by the layer-by-layer oxidation of the top surface of 2D HfS2. With this approach, 2D FG transistors can be easily fabricated by inserting the obtained HfOx/HfS2 heterostructure between the channel and gate dielectric of MoS2 transistors, exhibiting a high on/off current ratio of ∼ 107, a large memory window of 14.5 V, and a data retention time exceeding 104 seconds. Moreover, HfOx/HfS2-based 2D FG transistors show synaptic behavior with high linearity in both potentiation and depression during the repeated cycles up to 50 times. A high recognition accuracy of ∼90.25% is achieved in the CIFAR-10 data set simulation based on the experimental data.

Contact electrification (CE) remains a critical challenge in advanced material technologies where uncontrolled surface charging can compromise manufacturability, reliability, and performance of the materials for practical applications. Ultrathin glass with micrometer-scale thickness is a state-of-the-art specialty oxide material for flexible touchscreens in new-generation electronic devices. Despite extensive studies on CE on thermally grown oxide thin films, the physical and chemical properties of the stand-alone ultrathin oxide materials could be very different and thus lead to distinct CE behaviors. Such behaviors have not been experimentally investigated due to the challenge of their ultrathin form factor as well as the lack of experimental methods that would allow the successful study of CE on stand-alone ultrathin glass materials. Here, we, for the first time, visualize and quantify CE-induced surface charges on ultrathin glasses using sideband-mode Kelvin probe force microscopy (KPFM). To enable the KPFM measurement, we have established experimental strategies, including electrode preparation enabling the measuring circuit, and surface cleaning procedures improving surface activation and hydrophilicity. Nanosized atomic force microscopy (AFM) probes were used to scan and induce triboelectric charges on the stand-alone glass surfaces with a variety of thicknesses (30-100 μm) under ultrapure N2 conditions. Time-dependent measurements reveal the surface charges on a 30 μm-thick glass sample decay from 4.47 to 0.37 V in 240 min. Moreover, we found that electrostatic charges exhibit a capacitor-like discharging behavior primarily through the bulk material yielding a long relaxation time constant of ∼41 min, which is different from the lateral surface discharging behavior in a thermally grown SiO2 thin film reported previously. Furthermore, the thickness-dependent surface charging effect was characterized for the ultrathin glass substrates, where the change in contact potential difference between the charged and uncharged region (ΔVCPD) was found to remain nearly constant across this thickness range from 1.39 ± 0.17 V at 30 μm to 1.34 ± 0.29 V at 100 μm. A self-capacitance analytical model was developed and employed to estimate the corresponding surface charge density (σ), yielding comparable values of 136.26 ± 16.25 μC/m2 at 30 μm and 131.44 ± 28.41 μC/m2 at 100 μm. Additionally, the external bias applied to the AFM tips can be used to enhance, suppress, or invert the intrinsic CE response of glass materials. This work extends nanoscale CE characterization beyond oxide thin films to stand-alone oxide materials, providing a framework to understand and manipulate electrostatic charging in glass systems for practical applications.

Abstract Thin inorganic films, such as metal oxides, are frequently employed as functional materials for decoupling or optimisation of the interaction between molecular magnetic layers and metallic surfaces. In the case of single-molecule magnet (SMM) deposits, an effective decoupling layer can reduce the hybridisation with the metallic substrate, which would otherwise suppress their intrinsic magnetic bistability. In this work, we investigate the potential of an ultra-thin Fe oxide layer as a substrate for the terbium(III) bis-phthalocyaninato (TbPc 2 ) SMM in technological platforms. A multi-technique approach was employed to evaluate the integrity of a TbPc 2 sub-monolayer deposit and to determine the molecular adsorption geometry at the surface. Furthermore, large-scale facilities experiments were performed, and X-ray magnetic circular dichroism was used to probe the magnetic properties of the TbPc 2 sub-monolayer. Similar to what is observed on metallic surfaces, a suppression of the slow relaxation mechanisms in TbPc 2 is detected. The central finding is that while the magnetic moments and electronic configuration of the molecule are preserved, the characteristic slow magnetic relaxation is suppressed. This highlights the critical role of substrate phonon stiffness and tunnel barrier thickness in stabilizing the SMM behavior.

Oxide semiconductors have emerged as common channel materials in transistors and hold promise for next-generation electronics, yet achieving high mobility typically requires costly vacuum-based techniques. Here, ultrathin (5 nm) indium native oxide (InOx) prepared by ambient-air liquid-metal printing (LMP) at a low temperature (250 °C) is applied as a semiconducting channel in a field-effect transistor (FET). The resulting InOx is found to be polycrystalline, with large lateral grains that extend vertically throughout the film thickness. InOx FETs in a transfer length method configuration demonstrate a high conductivity mobility (μCON) of 125 cm2 V-1 s-1, with systematic analysis of contact resistance confirming the potential for channel length scaling. Integration with atomic-layer-deposited gate dielectrics further reveals excellent compatibility; for instance, an InOx FET integrated with HfO2 exhibits a high field-effect mobility (μFE) of 107 cm2 V-1 s-1, an on/off current ratio (ION/IOFF) of >107, a subthreshold swing (SS) of 204 mV dec-1, and a gate leakage of <10-6 A cm-2, while maintaining stable performance over 104 endurance cycles without degradation. Postfabrication oxygen plasma treatment is applied to achieve enhancement-mode operation, and a depletion-load inverter is demonstrated, exhibiting a voltage gain of 69.8 V/V. These results demonstrate the great potential of LMP InOx as a semiconducting channel in high-performance and power-efficient transistors for next-generation oxide electronics.

Developing multifunctional photoelectric synapses provides an effective solution for further improving the computational speed and integration of chips. However, conflicts in working mechanisms between photodetection and photoelectric synapses block the way to achieve both high responsivity and significant synaptic characteristics. In this work, InGaN core-shell nanorods-based wide-spectrum multifunctional synapses with an ultrathin oxide layer have been designed and prepared. Validated through multiple characterization techniques and density functional theory (DFT) calculation, the trap levels introduced by the oxide layer enable the regulation of the carrier relaxation time. Benefiting from both gradient indium composition and tunable carrier relaxation time, multifunctional integration of wide-spectrum response and synaptic plasticity is achieved, which allows the synapses to switch by merely modulating the incident light wavelength. In photodetector mode, the synapses have a wide-spectrum response spanning from visible to infrared light, which reveals a peak responsivity of 31.47 A/W and an ultrafast response time of 190/240 µs under 5 V bias and 810 nm illumination. In photoelectric synapse mode, the synapses exhibit tunable and stable synaptic plasticity under 365 nm illumination. Consequently, the synapses' multi-functionality is demonstrated through applications in both dual-band encrypted light communication and handwritten digit image recognition, achieving an accuracy of 89.12%.

The present study investigates the morphology, chemical composition, and phase constitution of oxide scales formed on the Fe40Al5Cr0.2TiB intermetallic alloy after long-term oxidation at 700 °C for 2000 h in air and water vapor environments. The results demonstrate the formation of an extremely thin oxide scale (≈300 nm), composed predominantly of α-Al2O3, which provides effective protection against further oxidation. The oxide layer exhibits locally heterogeneous morphology, including whisker-like structures and fine crystallites. Due to the very limited thickness of the oxide scale, significant challenges arise in the interpretation of microanalytical data. It is shown that the accelerating voltage strongly influences the effective information depth in SEM-EDS analysis, leading to a substantial contribution from the substrate even at low voltages. Monte Carlo simulations were used to support the interpretation of electron-matter interactions and to explain the observed discrepancies in chemical analysis. The study demonstrates that reliable characterization of ultrathin oxide scales requires careful optimization of SEM parameters and the combined use of complementary techniques, including EDS/WDS, XRD, and EBSD. The findings highlight the importance of methodological considerations in the analysis of thin oxide layers and provide guidance for the correct interpretation of experimental data in similar systems.

Ultra-thin p-type nickel oxide films grown by reactive pulsed laser deposition at room temperature: production of a pn heterojunction

A universal FIB approach for contamination- and damage-free plan-view TEM lamellae using NaCl sacrificial layers.

Photochemically-driven high-entropy oxide interphase for stable alkali-metal anodes.

Influence of process parameters on the sheet resistance and transmittance of ultrathin Indium Tin Oxide (ITO) films

Although optoelectronic memristors with nonvolatile bipolar photoconductivity enable in-sensor vision-centric neuromorphic hardware, achieving wavelength-defined polarity inversion across a broad spectrum remains a challenging task. Herein, a stable optoelectronic memristor composed of nonstoichiometric lead oxide (PbOx) coated black phosphorus (BP) nanosheets is demonstrated. The optoelectronic processes in the PbOx-BP heterostructure result in programmable polar photoresponses across the 365nm - 1,550nm wavelength range. Visible light causes positive photoconductance via photoelectrochemical Ag+ reduction and conductive filament reconstruction. Conversely, ultraviolet light drives the reverse photogenerated electron transfer to chemically oxidize the Ag CFs, while infrared light induces their localized melting via the photothermal effect. This bipolar optoelectronic tunability enables all-optical Boolean logic operations, allowing for the realization of 14 binary functions through optical reconfiguration. Furthermore, multispectral computing tasks, including edge extraction and spectral noise suppression, are performed, yielding a classification accuracy of up to 98.6% for 16 crop species using an all-optical convolutional neural network. The ultra-thin oxide coating presents an effective surface modification approach to improve two-dimensional devices, while the optoelectronic bipolarity establishes a framework for all-optical modulation in neuromorphic machine vision.

The glycerol electro-oxidation reaction (GEOR) to formate represents an attractive technology for the concurrent production of hydrogen and the valorization of biomass. However, the intricate pathway of GEOR and the high cost associated with noble metal electrocatalysts hinder its progress. Herein, ultrathin CuCoNiW medium-entropy oxide nanosheets (CuCoNiWOx UNS) serve as an effective noble-metal-free catalyst for this transformation. It delivers a high mass activity mass activity of 632.9 mA mgmetal–1, a low potential of 1.0 V vs RHE at 10 mA cm–2, and a formate selectivity of 83.1%, with remarkable stability over 40 h. The high performance is attributed to the distinct roles of each metal within the medium-entropy structure: subsurface W atoms ensure structural stability; Co and Ni sites optimize the adsorption of glycerol and intermediates; and Cu sites promote C–C bond cleavage. The reaction pathway involves the sequential conversion of glycerol to glyceraldehyde, glyceraldehyde to glycolaldehyde/formate, and glycolaldehyde to formate. These findings emphasize the efficacy of implementing medium-entropy structures as a viable strategy for biomass electrooxidation reactions.

A single-crystal high-entropy oxide provides an ideal structure to explore how multication substitution affects magnetic properties. In this study, several ultrathin La-based low-, medium-, and high-entropy perovskite oxides (ABO3) are synthesized through entropy engineering. The B-site cations in the single-crystal ABO3 structure are occupied by transition metals (Mn, Cr, Cu, Co, Ni, and Fe). The effects of multiple B-site substituents on the magnetic properties of the ultrathin nanosheets are extensively characterized via x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and magnetic measurements. Some samples of La(MnFeCoNi)O3, La(CuMnFeCoNi)O3, and La(CrMnFeCoNi)O3 exhibit a notable magnetic phase transition from ferromagnetic to paramagnetic states, along with a remarkable enhancement in coercivity. Moreover, these ultrathin samples display low magnetic ordering temperatures due to the structure–magnetic property correlations rather than epitaxial strain, demonstrating flexible and maneuverable magnetic responses.

An atom-edged magnetic nanomotor for cancer mechanotherapy.

Ultrathin amorphous oxide semiconductors are emerging materials being considered for transistors in memory and various back-end-of-line applications, but their stability remains a concern. Here, we report on both positive and negative bias temperature stability of top-gated indium tin oxide (ITO) transistors whose ultrathin, ~4 nm, channel was deposited with three oxygen compositions (10%, 14%, and 18% O2 partial pressure). No correlation between mobility and stability of such ITO transistors is apparent at room temperature, as we achieve highly stable (∼10 mV threshold voltage shift) devices with good mobility (∼38 cm2 V−1 s−1). We also investigate the time-dependent stability of such ITO transistors at elevated temperatures (85 and 120 °C). We discuss the interplay of multiple physical mechanisms and uncover the effect of processing conditions, leading to oxygen-related defects in the channel and gate dielectric, causing the subsequent instability.

Amorphous n-type metal oxides, such as In2O3 and Indium Gallium Zinc Oxide (IGZO), have shown promise as back-end-of-line (BEOL) compatible transistors, potentially offering a new paradigm for monolithic 3D stacking. However, a high-performance p-type counterpart remains a critical bottleneck. Tellurium suboxide (TeOx) has recently been shown to be a promising p-type semiconductor for BEOL applications. Yet, it remains to be seen if sub-10 nm TeOx films, needed for practical device applications, can be achieved with acceptable hole mobilities. Here, we report ultrathin TeOx transistors fabricated via cryogenic thermal evaporation at a substrate temperature of -80 °C. This low-temperature process suppresses crystallization and surface diffusion, yielding ultrasmooth films with root-mean-square roughness as low as 4 Å. The back-gated TeOx transistors achieve an on/off current ratio of 105 and a field-effect mobility of 2.8 cm2 V-1 s-1 at a channel thickness of 5.5 nm, retaining p-type switching behavior down to 2.4 nm. Selenium alloying further enhances the on/off current ratio by an order of magnitude while enabling bandgap tuning without compromising mobility.

Hydrogen-doped indium oxide (IHO) is a unique photonic material because of its high carrier mobility, strong plasma dispersion effect, and low optical absorption at both visible and near-infrared wavelengths. Existing research has mostly focused on films thicker than 100 nm, which is different from their potential role as an electro-optic material in photonic integrated circuits, where ultrathin films are required. This study examined IHO films with thicknesses ranging from 6 to 88 nm by characterizing their morphologies, electrical, and optical properties. The carrier mobility increased from 36 to 112 cm 2 /V·s with increasing thickness owing to the reduced grain boundary electron scattering. Additionally, we observed that IHO films thinner than 25 nm exhibited significant mobility loss after 8 months of exposure to air but were fully recovered by re-annealing at 230 °C in a nitrogen gas environment, which might be attributed to reactivated hydrogen dopant.

While metal-oxide interfaces can profoundly modulate the performance of (electro)catalysts, their dynamic nature under operational conditions remains poorly understood, and a compromise between activity and stability persists as a central challenge. Herein, we reveal a dynamic, "breathing" interface behavior in MOx/Pt (M = In, Sn, Sb) systems during the cathodic oxygen reduction reaction (ORR) in proton-exchange membrane fuel cells. By constructing well-defined Pt octahedra decorated with ultrathin p-block metal oxide overlayers, we demonstrate that an oxygen-deficient M-Pt interface forms at reducing potentials and improves the ORR activity following a trend of In-Pt > Sn-Pt ∼ Sb-Pt via interfacial charge transfer, while oxidizing potentials generate an oxygen-enriched M-O-Pt structure that effectively suppresses Pt dissolution and improves catalytic durability, particularly with SnOx overlayers. We further validate that harnessing the dynamic metal-oxide interfaces represents a new and generalizable strategy to break the activity and stability trade-off for a wide range of shaped or non-shaped Pt and Pt-bimetallic catalysts, most notably in InSnOx-decorated PtCo catalysts.

Two-dimensional (2D) materials are considered promising candidates for next-generation electronic devices, especially field-effect transistors (FETs). However, deposition of a uniform dielectric layer on 2D materials with an inert surface is challenging. Herein, the integration of HfOx on graphene is demonstrated through simple thermal oxidation of HfS2 precursor to form a high-quality HfOx/graphene stack. The thermal treatment enables complete conversion from HfS2 into ultrathin HfOx with an atomically smooth surface and sharp interface with graphene. The transformed thin HfOx shows decent dielectric properties, including a high dielectric constant of 18 and a robust breakdown field of 10 MV/cm. High-performance MoS2 FETs based on HfOx/graphene gate stack demonstrate a high ON/OFF ratio of 106, a low subthreshold swing of 75 mV/dec, and a low leakage current. Resistive switching devices were also fabricated showing coexistence of volatile and nonvolatile switching, and a steep switching slope. This nondestructive integration of high-quality high-κ dielectrics on 2D materials opens up possibilities for developing multifunctional 2D electronics.