Triboelectric nanogenerators (TENGs) are electronic devices capable of harvesting low-frequency mechanical motions to produce electrical energy through the triboelectrification effect. A great number of electronic devices, such as wearable devices, implantable medical devices, and monitoring sensors, among others, use conventional power sources such as batteries and capacitors. They are usually toxic, nondegradable, and hard to recycle, representing human and environmental hazards. In addition, conventional batteries and capacitors are usually rigid, heavy, and not suitable for the fabrication of portable and flexible devices. TENGs appear as a promising option to be used in the development of light, portable, and self-powered electronic devices. TENGs were first developed using synthetic polymers such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polydimethylsiloxane (PDMS), and polyimide (Kapton) for the fabrication of the active surfaces that store charge. Bio-TENGs have been fabricated using biopolymers such as cellulose, silk, and chitosan. These Bio-TENGs take advantage of the inherent biodegradability and biocompatibility of biopolymers. In order to improve the capability of biopolymer-based surfaces to store electrostatic charge, several treatments are reported, including the incorporation of nanoparticles and surface treatments. These biopolymer-based active surfaces with improved properties allow Bio-TENGs to achieve output performances similar to those reported for synthetic TENGs. Bio-TENGs have been used in a wide range of applications, such as human monitoring systems, tissue engineering, electronic devices, and industrial-level flooring, among others. This review is focused on the development of Bio-TENGs. The different types of biopolymers used for the fabrication of active surfaces are described and classified as protein-based, polysaccharide-based, and synthetic-based biopolymers. The different strategies used for improving the triboelectric properties of biopolymer-based surfaces are presented, along with the resulting output performance of Bio-TENGs. The reported applications for these Bio-TENGs are also discussed.

Elastomer-based piezoresistive sensors are an impactful and promising means of monitoring biological motion, tracking biosignals, and measuring the mechanical collision of physical stimuli in robots or machines. Piezoresistive behavior is generally realized when conductivity is imparted to elastomers, which results in resistivity changes by an external force that induces elastic deformations. Piezoresistive behavior of an elastomer can be achieved by mixing or coating the elastomer with a conductive material, thereby forming a composite structure. In this review, the conductive and elastic components that may determine the performance of a sensor are introduced. Conductive materials are classified into metal fillers, carbon allotropes, and hybrid materials, while elastic structures are classified into nonperiodic/periodic, hierarchical, and textile-based formations. Then, this comprehensive review focuses on textile-based structures for flexible applications, emerging challenges, potential strategies, and finally, the proposed hybrid mechanisms.

Carbonization of epoxy resin under high voltage discharge or exposure to high temperatures results in insulation failure. Herein, multiscale spherical boron nitride (SBN) epoxy resin is developed with improved anticarbonization properties. The thermal conductivity, thermostability, dielectric performances, volume resistivity, breakdown strength, and flame retardancy of the epoxy-SBN composites were studied. The thermal conductivity, thermostability, volume resistivity, and breakdown strength of epoxy-SBN composites are higher than that of pure resin, with a ratio of high thermal conductivity of 24 and a volume resistivity of ∼10. The AC breakdown voltage of the epoxy-30SBN composites was as high as 29.96 kV/mm. In addition, epoxy-30SBN composites possess minimal carbonization surface area under high-voltage discharge. Increased thermal conductivity, lower mass loss rate, high flame resistance, and inhibited charge carrier migration contribute to the improved carbonization resistance of the arc. Densified SBN networks in epoxy resin act as a dense barrier to achieve anticarbonization under high voltage stress or high-temperature exposure. Therefore, epoxy-SBN composites are promising candidates for application in next-generation high-voltage devices to ensure electrical safety.

We have studied the effect of barrier-controlled electrodes on characteristics of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) using an interlayer with modulated oxygen defects. Interlayers of a-IGZO with different electrical resistivities were controlled with various oxygen ratios during the RF sputtering deposition. As the ratio of O2/(O2 + Ar) was increased from 0 to 20%, the carrier concentration decreased from 2.84 × 1018 to 1.56 × 1014 cm–3 and the electrical resistivity increased from 0.12 to 9600 Ω·cm. Using this result, a-IGZO thin layers with different resistivities (low and high) to control the contact barriers were inserted between the a-IGZO TFT channel and both the source and drain electrodes. In the case of a-IGZO TFT with a low resistivity interlayer, the threshold voltage (Vth) was shifted by −4.1 V compared to the reference device without an interlayer. In addition, on/off ratio, the subthreshold swing, and the mobility of the devices were also enhanced by achieving Ohmic contact. In contrast, the a-IGZO TFT with a high resistivity interlayer showed a positive Vth shift of 1.5 V and also improved device performance, while maintaining a mobility of ∼84% of the reference device due to the energy barrier.

The rapid development of the clean energy industry has given great impetus to energy-efficient storage and conversion technologies. Film capacitors have attracted much attention because of their higher charge and release rates, greater energy density, and extended life cycle. But the lower recharging and discharging efficiency and insulation properties pertaining to the electricity used in capacitors limit the improvement of their energy storage performance. In this paper, the addition of the linear polymer polycarbonate (PC) to polyvinylidene fluoride (PVDF) through a blending strategy and the subsequent acquisition of the high-dielectric nanofiller titanium dioxide (TiO2) to the blended matrix is expected to achieve synergistic optimization of the insulation and polarization properties, thereby enhancing the energy storage performance of the mixed media. The findings show that great storage of energy productivity (Ue ≈ 11.43 J/cm3, η ≈ 57.08%) is obtained for 40 vol % PC/PVDF-x wt %-TiO2 at an optimum field strength of 450 kV/mm when the TiO2 doping amount x is 0.9 wt %. Compared with pure PVDF, its Ue is improved by 2.3 times, η by 1.2 times, and Eb by 1.5 times. This research presents a viable answer for applying PVDF-based high-energy-storage film capacitors.

High-performance blue perovskite quantum dots (PQDs) are of key importance for electroluminescent light-emitting diodes (LEDs) toward full color display in the future. Here, mixed halogen PQDs CsPb(Brx/Cl1–x)3 with a tunable emission wavelength was obtained through a strategy of ligand-assisted anion exchange assisted by didodecydimethyammonium chloride (DDAC) ligand. Surface Br– vacancies of the PQD are passivated by the halogen atoms in the anchored DDAC ligand, enabling a high efficiency emission of blue light from the PQD. Stable anchoring of the ligand also improves the robustness of the PQD during its purification in weak polar solvents. Well-controlled chlorine stoichiometry of the PQD also allows fine-tuning of its photoluminescence and electroluminescence spectra in the range of 424–514 nm and 453–500 nm. The external quantum efficiency of the fabricated PQDs LED device reaches 10.1% at 495 nm, 6.5% at 484 nm, and 5.1% at 470 nm (NTSC pure blue) under a constant current test. Our work provides a facile method without additional purification or ligand separation to achieve highly efficient blue PQDs with a tunable emission wavelength, promoting the advance of blue PQDs LED.

In this study, an interfacial switching (IFS)-based bioinspired TiN/AlON/TaON/Pt resistive random-access memory (RRAM) device was fabricated to investigate its conduction mechanism and synaptic behavior for neuromorphic computing. This device exhibited excellent dc endurance over at least 10000 cycles, an ac pulse endurance of 1 M, and long-term retention (106 s) at 150 °C with no degradation. The device also showed multilevel characteristics. The RESET stop voltage of the device varied from −0.9 to −1.3 V. The device was highly stable over 250 potentiation and depression cycles, which are crucial in Hopfield neural network (HNN)-based neuromorphic systems. High nonlinearity (1.13 for potentiation and −1.75 for depression) was achieved using the device potentiation and depression functions. Experimental potentiation and depression data were used to train an HNN based on the fabricated device to recognize an input image of 28 × 28 pixels that contained 784 synapses. The HNN had a training accuracy of higher than 93% in 22 iterations. The experimental results indicate that the fabricated IFS-based TiN/AlON/TaON/Pt RRAM device is highly suitable for neuromorphic devices that mimic synaptic characteristics for neuromorphic systems.

Measurement and optimization of interface states in metal oxide semiconductors are the premise of building high-performance and high-reliability field-effect transistors (FETs). Although FETs built on semiconducting carbon nanotube (CNT) films have been demonstrated as promising devices for many applications, including integrated circuits (ICs), thin-film electronics, and biosensors, systemic research on the interface state of CNT film FETs, including accurate measurement and optimization schemes, is lacking. In this work, we fabricate MOS capacitors with an area of 400 μm2 on a CNT network film with a Y2O3 gate dielectric and carry out admittance measurements to investigate electrically active traps near the Y2O3/CNT interface. Through the conductance method and high-low frequency method, we extract the energy-dependent interface trap density (Dit) and border trap density (Nbt) of CNT MOS FETs based on the measured admittance dataset. Postdeposition annealing (PDA) processes with different gases at 300 °C show the ability to lower the Dit and Nbt of the Y2O3/CNT interface and then improve the performance of CNT film FETs.

The attention toward cost-effective and high-performance H2S sensors is increasing due to the growing need for physical health and environmental monitoring. In this paper, Ag/WO3/reduced graphene oxide (rGO) nanocomposites were synthesized by using a microwave-assisted gas–liquid interfacial method. Nanomaterials with different Ag doping contents were successfully prepared with AgNO3 as an additive. The Ag/WO3/rGO sensors exhibit remarkable selectivity toward H2S, and the gas sensing performances of Ag-doped WO3/rGO gas sensors are significantly better than those of WO3/rGO. At 150 °C, the response value of the 10 wt % Ag/WO3/rGO gas sensor to 100 ppm H2S is 204.5, which is 7 times higher than that of WO3/rGO, and the response/recovery time of the sensor is 9/49 s, respectively. Additionally, the gas sensing performance of the sensor is further enhanced under ultraviolet (UV) irradiation. The response value is enhanced to 685.8, which is 3 times higher than that without UV irradiation, and the response/recovery time is reduced to 8/38 s, respectively. The sensing mechanism is also discussed. This work offers a potential application for H2S detection in environmental monitoring and smart healthcare.

Recent progress in topological insulating materials predicts a promising future for their applications in developing innovative quantum, electronic, and optoelectronic devices. The integration of topological insulators with technologically important semiconductors can open up different ways to build high-efficiency devices. Here, we have fabricated topological insulator Bi2Se3/GaN hybrid structure-based photodetectors (PDs) and studied their photoresponse characteristics in the ultraviolet (UV) region. Raman and high-resolution X-ray diffraction spectroscopy measurements revealed the formation of the c-axis-oriented rhombohedral crystal structure of the Bi2Se3 film. X-ray photoelectron spectroscopy studies disclosed the formation of a stoichiometric Bi2Se3 thin film on n-GaN. The Bi2Se3 thin film with the magnetotransport property exhibits a metallic nature with an upturn in resistivity below 20 K which possesses a weak antilocalization effect under an applied magnetic field, confirming the topological insulating behavior. Further, we have fabricated metal–semiconductor–metal-type PD devices on the hybrid structure of Bi2Se3/n-GaN, Bi2Se3/n-GaN junction, and pristine n-GaN. The photoresponse measurements have been performed using a UV (355 nm) light source by varying the laser power (1–15 mW) and the external bias (0–5 V). The calculated value of photoresponsivity of the PD devices on the Bi2Se3/n-GaN hybrid structure is found to be seven-fold higher than that of pristine-GaN. Further, it is observed that devices consisting of a Bi2Se3 film and GaN show self-powered UV PD characteristic nature. This study adds a significant step to enhance the performance of UV PDs based on large-area GaN templates by several folds with the help of topological Bi2Se3/GaN hybrid structures.

Herein, we present a straightforward and cost-effective procedure for producing conductive diamond tubes on the surface of porous carbon nanotube hollow fibers using successive 10-pulsed laser annealing shots and 6 h of hot filament chemical vapor deposition techniques. Room-temperature Raman and X-ray diffraction spectra reveal the signature T2g peaks near 1332.4 cm–1 and 111 planes of diamonds near 43.9°, respectively. A low turn-on field (ETO) ∼1.85 V/μm@1 μA/cm2 and a threshold field (ETH) ∼2.54 V/μm@10 μA/cm2 were observed for the tubular diamond structures. The field enhancement factor (β) was calculated at 3594 and highly stable field emission current stability was observed over a long period of 4 h. For the first time, a good insight into the field emission results of the diamond is established with the structural, electronic properties, and the work function (φ) ∼4.84 eV analysis conducted by the density functional theory simulation. Finite electronic states at the Fermi level are observed beyond a band gap, and it demonstrates the wide-band gap (4.4 eV) semiconducting nature of the diamond. The Bader charge analysis and maximum entropy method pattern revealed the negative electron affinity of the diamond, and it is responsible for the emission of electrons from the conduction band of the diamond. Besides, the accumulation of charge carriers, which contributes to the electric field emission, takes place due to the weak π bonds of carbon atoms. The low turn-on field, the high field enhancement factor, and the good field emission current stability of tubular diamond offer great prospects for future efficient and low-cost field emission devices.

Topological spin textures have drawn intense attention due to interesting fundamental physics and possible application in non-volatile information carriers as well as logic gate devices. Here, in a specially designed race track that consists of three narrow nanotracks connected to a wide nanotrack, we investigate the role of geometry in domain wall (DW) pair to skyrmion conversion using micromagnetic simulation. In particular, tunable DW to skyrmion or fractional skyrmion conversion is achieved for a selected material parameter with a separation length of 10 or 30 nm (or combination of both) between the narrow nanochannels. By suitably varying the spacing between the narrow nanotracks symmetrically and asymmetrically, we control the dynamics of skyrmions and fractional skyrmions along with the trajectory. Interestingly, if the separation length between the top and middle (or middle and bottom) nanochannel is 30 nm, a fractional skyrmion is formed. The DW pair to skyrmion conversion time depends on the separation between the narrow nanochannels, e.g., for 10 nm separation, the conversion time of DW pair to skyrmion from the top nanochannel is ∼0.3 ns, and the same for the 30 nm separation is ∼2 ns. Analysis of the topological number of spin texture suggests the creation of two skyrmions in the case of 10 nm separation between the narrow nanochannels, whereas for 30 nm separation, a skyrmion and a fractional skyrmion are formed. Furthermore, the analysis of total energy and other energy terms shows a non-monotonic variation during the conversion of DW to skyrmion at the junction. Finally, the increase or decrease in the total energy value depends on the formation of skyrmions or fractional skyrmions. Thus, we infer that the enforced geometrical constraints and the interplay of various energies play a crucial role in controlling the topology and skyrmion formation. Based on these findings, we believe that a skyrmion racetrack made up of three nanochannels will help achieve efficient controllable skyrmion dynamics, which may have application potential in magnetic memory operations.

CsPbCl3 metal halide perovskite photodetectors (PDs) are prepared via thermal evaporation and 75 °C in situ annealing on Si/SiO2 substrates, and their photoresponse as well as the morphology, structure, and photophysical properties are investigated. Wide spectrum photoresponse ranging from 350 to 980 nm has been achieved with optimal responsivity (R) of 2364, 3766, and 268 A/W at wavelengths (λ) of 420, 680, and 980 nm, respectively. Such photoresponse behavior can be attributed to the parallel photoresponse from both CsPbCl3 and Si based on the UPS (ultraviolet photoelectron spectrometry) and XPS (X-ray photoelectron spectroscopy) results. Yb3+ doped CsPbCl3 PDs with the photosensing layer structure of CsPbCl3 (50 nm)/YbCl3 (30 nm)/CsPbCl3 (50 nm) have been prepared, and it was found that Yb3+ dopant is capable of realizing obviously shorter exciton lifetime at 420 nm, lower trap density, as well as remarkably higher carrier mobility due to the combined effects of energy transfer from CsPbCl3 to Yb3+ and defect passivation from Yb3+, leading to remarkable improvement of the photoresponse performance with optimal R (2709, 6340 and 3573A/W), noise equivalent power (NEP) (5.64 × 10–7, 2.51 × 10–7, and 4.38 × 10–7 W), and specific detectivity (D*) (1.84 × 1011, 3.24 × 1011, and 1.5 × 1011 cm Hz1/2 W–1) compared to those of pristine CsPbCl3 at λ of 420, 720, and 980 nm, respectively. Especially at the NIR λ of 980 nm, 10-fold higher R is achieved after Yb3+ incorporation. The upconversion processing of Yb3+ can also be responsible for the enhanced wide spectrum photoresponse of Yb3+ doped CsPbCl3. Our study provides a practical way to realize wide spectrum perovskite PDs by simply connecting the perovskite to Si substrates by the Au electrodes.

We review the progress made in integrating magnetic molecules containing transition metal ions into nanoelectronic solid-state devices and using them as molecular spin qubits. Molecular spin qubits offer numerous advantages over other material platforms, such as being inherently quantum systems with discrete energy levels, having a rich variety of possible chemical designs, and being synthesizable in large quantities with atomic precision. However, the integration of magnetic molecules into practical and scalable molecular spin qubit devices (MSQDs) that offer initialization, coherent control, and readout of quantum spin states remains one of the major bottlenecks on the way toward applications of these systems in quantum computing technologies. We discuss the evolution of the field of MSQDs and review the first successful implementation of essential qubit operations in a single-molecule transistor based on a TbPc2 molecule. Further development has been achieved through the merging of molecular electronics with the circuit quantum electrodynamics (cQED) approach where molecular spin states can be manipulated by the microwave frequency photons confined in a superconducting waveguide resonator. We discuss examples of such hybrid devices operating via coupling of a superconducting resonator to large spin ensembles, such as bulk samples and thin films. We also review a possible architecture for single-molecule cQED devices and the potential advantages that it offers. Then, we highlight the possibility and benefits of the optical initialization and readout of molecular spin states. This approach has been realized by using an optical pumping technique for the initialization and changes in photoluminescence for the readout of large molecular spin ensembles coupled to a superconducting resonator. The field of MSQDs is highly interdisciplinary, bringing together progress in synthetic chemistry, molecular electronics, cQED, and optical measurements. While it is still in its infancy, there are promising theoretical designs and encouraging proof-of-concept experiments, and we discuss several proposed device architectures that are eagerly awaiting experimental realization. Advances in hybrid MSQDs will open horizons for quantum technologies.

Piezoelectric organic light-emitting diodes (p-OLEDs) are acousto-optic devices that enable direct visualization of ultrasound intensity profiles and pixel-free ultrasound imaging. However, there have been no reports since the initial report because the underlying physics has not been fully explained. In this study, we report the mechanism of p-OLEDs by elaborating on an alternating-current (AC)-driven operating environment. Strong light emission was observed from the p-OLED, although the ultrasound frequency (590 kHz) was significantly higher than the cutoff frequency (45 kHz) of our phosphorescent OLED. Such a contradictory result can be explained by an occurrence of a direct-current (DC) voltage offset or exceptionally large AC voltage generation in the OLED. We discovered that an AC voltage amplitude (VAC) as large as 16 V could be induced in the OLED by applying only 60 V of VAC to the transmitter, revealing the origin of the strong acousto-optical coupling, while the DC offset was not observed during the measurement. Based on this mechanism, we demonstrate that p-OLEDs made on the single-crystalline [Pb(Mg1/3Nb2/3)O3]1–x [PbTiO3]x substrate with a higher piezoelectric coefficient exhibit a considerably lower turn-on voltage and higher luminance compared to the case with the polycrystalline Pb(ZrxTi1–x)O3 substrate.

Doping of a small amount of La3+ into ferroelectric Bi2SiO5 induces the disorder of SiO4 chains in its crystal structure, leading to a transition into a paraelectric phase with a superior temperature stability of the dielectric permittivity. In this study, we attempted to fabricate bulk La-doped Bi2SiO5 ceramics through sintering with the aim of applying Bi2SiO5 to ceramic capacitors. (Bi1–xLax)2SiO5 fine powders with a La content x of up to 0.05 were synthesized by a sol–gel method and then sintered at low temperatures below 740 °C. The undoped Bi2SiO5 decomposed into secondary phases after sintering at temperatures over 640 °C due to its metastable nature, whereas La doping retarded the thermal decomposition, enabling sintering at higher temperatures. As a result, high relative densities near 90% were achieved for (Bi1–xLax)2SiO5 ceramics with x = 0.03 and 0.05 without the formation of secondary phases. The dielectric peak due to the ferroelectric–paraelectric phase transition at around 400 °C disappeared with the increase in La content. The obtained (Bi0.97La0.03)2SiO5 ceramic consequently exhibited a temperature-stable dielectric permittivity over a wide temperature range between −160 and 500 °C. A highly linear large-field dielectric response of the (Bi0.97La0.03)2SiO5 ceramic was observed under varying electric fields up to 220 kV cm–1 (at 20 °C) and at varying temperatures between −60 and 60 °C (at 100 kV cm–1).

In this study, we developed a Mo metal thin film deposition process consisting of two steps: Mo2N thin film deposition using plasma-enhanced atomic layer deposition, followed by rapid thermal annealing. The mechanism underlying the reduction of Mo2N during the post-deposition annealing was investigated. Agglomeration during the reduction of Mo2N to Mo was successfully suppressed by using a hydrogen-permeable mechanical capping layer. Finally, a Mo thin film formation process with low resistance, even at a thickness of 5 nm, was achieved.

The hole selectivity of molybdenum oxide (MoO3-x) in organic and inorganic heterojunction solar cells depends on its work function value. MoO3-x with a higher work function value has superior selectivity and facilitates the flow of holes through it. The oxidation state of the Mo atoms and the oxygen vacancy affect the work function of MoO3-x. Here, for the first time, thermally evaporated MoO3-x films are subjected to oxygen (O2) plasma treatment using a plasma-enhanced chemical vapor deposition method to tune the work function. The effect of O2 plasma treatment on work function is studied using Kelvin probe force microscopy. The work function of thick MoO3-x films increased from 4.91 ± 0.01 eV for as-deposited films to 5.22 ± 0.02 eV by proper tuning of rf power, oxygen flow rate, and O2 plasma treatment time. This increase in work function is accompanied with the increase in O/Mo ratio in these films as confirmed by EDX. Oxygen plasma treatment has also resulted in the enhancement of work function, transmittance, and band gap of thin (23 and 14 nm) MoO3-x films. An optimum increase in work function for thin films by ∼0.40 eV is observed for 5 min plasma treatment at 80 W rf power with a 30 SCCM oxygen flow rate. The studies suggest oxygen plasma treatment as an effective approach to recover or tune the work function of molybdenum oxide films.

Polymer semiconductors having solubility in organic solvents can enable facile, low-cost, and large-area solution processes to fabricate electronic devices with various applications. However, it has been a challenge to build complicated circuits by using them due to device-to-device variation. In this study, we designed a diketopyrrolopyrrole (DPP)-based polymer with long and branched alkyl side chains to improve the solubility of DPP polymers. While the long and branched side chains are introduced to the DPP moieties for improved solubility, the far branching point in the side chains was expected to prevent severe steric hindrance of the long side chains and to allow DPP moieties to have π–π interactions and form crystalline structures. To examine the feasibility of using P29DPP-TT as a semiconductor in integrated electronic systems, the electrohydrodynamic (EHD) jet printing technique was used in for local area patterning. The organic field-effect transistors (OFETs) incorporating EHD-printed P29DPP-TT yield promising field-effect mobility (μFET) of 0.55 cm2 V–1 s–1. Complementary inverters and NAND/NOR logic gates were also realized by fabricating OFETs with line-printed P29DPP-TT and polymer gate dielectrics. It indicates that P29DPP-TT with excellent solubility can be applied to solution-processed integrated electronic devices.

The resistivity of halogen-free atomic layer deposition (ALD) TiN thin films was decreased to 220 μΩ cm by combining the use of a high-thermal stability nonhalogenated Ti precursor with a highly reactive nitrogen source, anhydrous hydrazine (N2H4). TDMAT [tetrakis (dimethyl-amino)titanium], TDEAT [tetrakis(diethylamido)titanium], and TEMATi [tetrakis (ethylmethyl-amido)titanium] were compared to TiCl4 as precursors for ALD TiN using N2H4 as a coreactant. By minimizing the pulse length of the Ti-source precursor and optimizing the deposition temperature, the resistivity of TiN thin films deposited using these precursors was reduced to 400 μΩ cm for TDMAT (at 350 °C), 300 μΩ cm TDEAT (at 400 °C), and 220 μΩ cm for TEMATi (at 425 °C) compared to 80 μΩ cm for TiCl4 (at 500 °C). The data are consistent with the lowest resistivity for halogen-free ALD corresponding to the organic precursor with the highest thermal stability, thereby allowing maximum ALD temperature. After optimization, TiN thin films were grown in horizontal vias, illustrating conformal and uniform TiN using both TiCl4 and TEMATi in horizontal vias in patterned substrates.