High‐quality lead sulfide (PbS) films are deposited on selected substrate chemistries by an H2S‐free metal‐organic chemical vapor deposition (MOCVD) process using a single‐source metal‐organic ...complex (Pb(dmampS)2). The complex is synthesized via a salt metathesis reaction between PbCl2 and lithium 1‐(dimethylamino)‐2‐methylpropane‐2‐thiolate (Li(dmampS)) in diethyl ether. Subsequent film deposition is conducted by a simple thermolysis process in the absence of H2S, yet chemical and structural analysis confirm chemically stoichiometric and homogenous films. Mechanistic studies with electron impact mass spectroscopy (EIMS) and gas chromatography mass spectroscopy (GCMS) suggest the selective cleavage of C−S bonds in the complex as the reason for the facile PbS formation with negligible impurity incorporation. The high crystallinity, low hole concentrations, and charge transport properties comparable and in many cases superior to films produced by atomic layer deposition (ALD) testify to the quality of the films. Lastly, rigid and flexible photodetectors fabricated with the PbS films exhibit considerably high photocurrents, reliable switching characteristics, and high sensitivity over a broad spectral bandwidth, highlighting the potential for realizing practical broadband photodetectors.
Chemically stoichiometric and homogeneous PbS films are deposited by H2S‐free metal‐organic chemical vapor deposition using a single‐source metal‐organic complex (Pb(dmampS)2). The facile PbS formation with negligible impurity incorporation is achieved by the selective cleavage of C–S bonds in the complex. Photodetectors based on the PbS films exhibit reliable switching characteristics and high photoresponsivity over a broad spectral bandwidth.
The precisely tailored refractive index of optical materials is the key to utilizing and manipulating light during its propagation through the matrix, thereby improving their application ...performances. In this paper, mesoporous metal fluoride films with engineered composition (MgF
:LaF
) are demonstrated to achieve finely tunable refractive indices. These films are prepared using a precursor-derived one-step assembly approach via the simple mixing of precursor solutions (Mg(CF
OO)
and La(CF
OO)
); then pores are formed simultaneously during solidification owing to the inherent instability of La(CF
OO)
. The mesoporous structures are realized through Mg(CF
OO)
and La(CF
OO)
ions, which interacted with each other based on their electrostatic forces, providing a wide range of refractive indices (from 1.37 to 1.16 at 633 nm). Furthermore, it is systematically several MgF
-LaF
layers with different compositions (x = 0.0, 0.3, and 0.5) to form the graded refractive index coating that is optically consecutive between the substrate and the air for broadband and omnidirectional antireflection. An average transmittance of ≈98.03% (400-1100 nm) is achieved with a peak transmittance of ≈99.04% (at 571 nm), and the average antireflectivity is maintained at ≈15.75% even at an incidence of light of 65° (400-850 nm).
Van der Waals (vdW) heterostructures have drawn much interest over the last decade owing to their absence of dangling bonds and their intriguing low‐dimensional properties. The emergence of 2D ...materials has enabled the achievement of significant progress in both the discovery of physical phenomena and the realization of superior devices. In this work, the group IV metal chalcogenide 2D‐layered Ge4Se9 is introduced as a new selection of insulating vdW material. 2D‐layered Ge4Se9 is synthesized with a rectangular shape using the metalcorganic chemical vapor deposition system using a liquid germanium precursor at 240 °C. By stacking the Ge4Se9 and MoS2, vdW heterostructure devices are fabricated with a giant memory window of 129 V by sweeping back gate range of ±80 V. The gate‐independent decay time reveals that the large hysteresis is induced by the interfacial charge transfer, which originates from the low band offset. Moreover, repeatable conductance changes are observed over the 2250 pulses with low non‐linearity values of 0.26 and 0.95 for potentiation and depression curves, respectively. The energy consumption of the MoS2/Ge4Se9 device is about 15 fJ for operating energy and the learning accuracy of image classification reaches 88.3%, which further proves the great potential of artificial synapses.
Ge4Se9, a new insulating 2D‐layered material, is synthesized using metal–organic chemical vapor deposition at 240 °C with low‐reactive precursors. The 2D‐layered Ge4Se9 forms a low band offset with MoS2, exhibiting a large memory window with linear gate‐tunability. As an artificial synapse, the MoS2/Ge4Se9 heterostructure exhibits synaptic updates with low non‐linearity of 0.26 and low energy consumption of 15 fJ.
The vast possibilities in the elemental combinations of high‐entropy alloys (HEAs) make it essential to discover activity descriptors for establishing rational electrocatalyst design principles. ...Despite the increasing attention on the potential of zero charge (PZC) of hydrogen evolution reaction (HER) electrocatalyst, neither the PZC of HEAs nor the impact of the PZC on the HER activity at HEAs has been described. Here, we use scanning electrochemical cell microscopy (SECCM) to determine the PZC and the HER activities of various elemental compositions of a Pt−Pd−Ru−Ir−Ag thin‐film HEA materials library (HEA‐ML) with high statistical reliability. Interestingly, the PZC of Pt−Pd−Ru−Ir−Ag is linearly correlated with its composition‐weighted average work function. The HER current density in acidic media positively correlates with the PZC, which can be explained by the preconcentration of H+ in the electrical double layer at potentials negative of the PZC.
Scanning electrochemical cell microscopy (SECCM) experiments on a thin‐film Pt−Pd−Ru−Ir−Ag high‐entropy alloy materials‐library (HEA‐ML) reveal that the potential of zero charge (PZC) of different compositions of the Pt−Pd−Ru−Ir−Ag HEA has a linear correlation with its composition‐weighted average of the work function, and positively correlates with its hydrogen evolution reaction (HER) activities in acidic media.
New heteroleptic indium complexes, i. e., MeIn(mdpa)(tmhd)2 (2), MeIn(mdpa)(acac)2 (3), MeIn(edpa)(tmhd)2 (4), and MeIn(edpa)(acac)2 (5), with three different ligands, bearing N‐alkoxy carboxamide ...and β‐diketonate were designed and synthesized as indium precursors for indium oxide thin films by atomic layer deposition (ALD) using Me2In(edpa)2 and Me2In(mdpa)2 (1) as starting materials. The resulting complexes were characterized by NMR and FT‐IR spectroscopy, elemental analysis (EA), thermogravimetric analysis (TGA), and single crystal X‐ray diffraction. TGA curves of all the complexes showed clear single‐step weight losses, with low residual masses of 7–13 %. Among them, complex 5 was volatile and thermally stable, and thus, it can be used as potential indium precursor for indium oxide‐based thin films.
New heteroleptic indium complexes that include three different ligands, methyl, N‐alkoxy carboxamide, and β‐diketonate, have been designed and successfully synthesized for use in the preparation of In2O3‐based thin films.
Iontronics is an emerging technology based on sophisticated control of ions as signal carriers that bridges solid-state electronics and biological system. It is found in nature, e.g., information ...transduction and processing of brain in which neurons are dynamically polarized or depolarized by ion transport across cell membranes. It suggests the operating principle of aqueous circuits made of predesigned structures and functional materials that characteristically interact with ions of various charge, mobility, and affinity. Working in aqueous environments, iontronic devices offer profound implications for biocompatible or biodegradable logic circuits for sensing, ecofriendly monitoring, and brain-machine interfacing. Furthermore, iontronics based on multi-ionic carriers sheds light on futuristic biomimic information processing. In this review, we overview the historical achievements and the current state of iontronics with regard to theory, fabrication, integration, and applications, concluding with comments on where the technology may advance.
We herein achieved a novel indium-tin oxide (ITO) bipolar electrode (BPE) based sensing system by the introduction of nanoporous ITO on the cathode. The implementation of the nanoporous ITO layer in ...the BPE greatly boosted the ECL signal compared to the planar ITO BPE, enabling efficient detection of H2O2 even under mild operating voltage. The calibration curves of ECLs in H2O2 sensing with BPEs of various nanopore thicknesses exhibited enhancement of LODs and sensitivities with a thicker nanoporous ITO layer. We speculate that the morphology of the nanopores led to confinement of the analytes, increasing the interaction with the electrode surface, resulting in amplified ECL signals. We believe that the nanoporous BPEs are adequately suited for the extended application as a compartment in portable, in situ sensing systems, due to their low power requirements and ease of detection through the naked eye.
Display omitted
Dynamic random-access memory (DRAM) capacitor electrodes, exemplified by TiN, face performance limitations owing to their relatively low work functions in addition to the formation of a low-k ...interfacial layer caused by their insufficient chemical stability. With recent advances in device scaling, these issues have become increasingly problematic, prompting the exploration of alternative electrode materials to replace TiN. Molybdenum dioxide (MoO2) has emerged as a promising candidate for this application, outperforming TiN due to its low resistivity, high work function (>5 eV), and excellent chemical stability. Moreover, monoclinic MoO2 exhibits a distorted rutile structure, enabling the in situ growth of high-k rutile TiO2 on MoO2 at low deposition temperatures. However, MoO2 deposition poses challenges because of its metastable nature compared to the more stable molybdenum oxide (MoO x ) phases, such as MoO3 and Mo4O11. In this work, we successfully fabricated Sn-doped MoO x (TMO) films by atomic layer deposition (ALD) at 300 °C. A stabilized monoclinic MoO2 phase was achieved using ALD by incorporating SnO x into MoO x on both SiO2 and TiN substrates. The ALD TMO process comprised MoO x and SnO x subcycles, and the MoO x :SnO x subcycle ratio was varied from 100:1 to 20:1. High growth rates ranging from 0.19 to 0.34 nm/cycle were achieved for ALD TMO with varying the MoO x :SnO x subcycle ratio from 20:1 to 100:0. After post-deposition annealing at 500 °C, polycrystalline TMO films were obtained with smooth surface morphology. ALD TMO exhibited excellent interface quality with ALD TiO2, possessing a negligible low-k interfacial layer. Moreover, a rutile TiO2 film with a high dielectric constant of 136 was successfully grown on a 20% Sn-TMO electrode. Overall, this study provides a strategy to stabilize metastable MoO2 films using ALD, and it demonstrates the superiority of ALD TMO as a promising DRAM capacitor electrode material.
As the demand for soft and flexible devices steadily increases, the ionic applications demonstrated with gel materials have come under the spotlight. Here, stretchable and wearable ionic diodes ...(SIDs) made from polyelectrolyte hydrogels are introduced. Polyelectrolyte hydrogels are mechanically modified using methacrylated polysaccharides while preserving the ion‐permselectivity of poly(sulfopropyl acrylate) potassium salt (PSPA) and poly(acrylamidopropyltrimethylammonium chloride) (PDMAPAA‐Q), forming ionic copolymers. Then, SIDs composed of polyelectrolyte copolymer hydrogels are fabricated in VHB substrates as a stretchable and transparent insulating layer which is engraved by a laser. The SIDs show rectifying behaviors beyond the stretch of 3 with the aid of perfect adhesion between hydrogels and elastomeric substrates, and preserve their rectifications over hundreds of cycles. The operation of the SID is visualized by a wearable ionic circuit which rectifies ionic currents and lightens the LED under the forward bias during finger movements.
A stretchable ionic diode is demonstrated from polyelectrolyte hydrogels. Polyelectrolyte gels are mechanically modified with maintaining their own ion‐selective properties to generate a P–N junction. With the aid of perfect adhesion between the hydrogel materials and an elastomeric substrate, ionic diodes can rectify ionic currents under the applied stretch beyond 3.
Despite numerous reports on iontronic devices, there has been no whole circuit working in aqueous media including even power source. Herein, we introduce complete ionic circuits powered by reverse ...electrodialysis (RED) for the first time without employing any electronic components. The RED-driven polyelectrolyte diode successfully shows rectification behavior which is verified by monitoring dynamic ion distribution through fluorescence in real-time. We can also turn on and off the voltage applied to the circuit, and apply an arbitrary voltage by precisely manipulating the pressure imposed to an elastic connection tube filled with electrolyte. Furthermore, this new concept containing ionic power source advances to a more sophisticated ionic OR logic gate. The proposed system paves the way to develop not only passive iontronic devices (e.g. current ionic diode), but active ones requiring a source of energy, particularly such as a neuron-like information processor powered by fully ionic systems, and thereby aqueous computers.
PDF