Device Area Research Articles

Ovonic threshold switching device and its application to logic gate function and steep slope in field effect transistors

We report the poly(p-vinylphenol) (PVP)-based ovonic threshold switching devices. By optimizing the effective device area of the PVP-based device, low threshold voltage and low threshold voltage variation were achieved. By changing the compliance current to affect the strength of the conductive filaments, the threshold switching characteristics of the devices were tested at four different compliance currents of 1 × 10−4 A, 5 × 10−5 A, 1 × 10−5 A, 5 × 10−6, the results show that the lower the limiting current, the lower the on state current. The PVP-based device is used in the design of logic gates to realize the function of “AND” and “OR”. Furthermore, a steep slope FET was realized by connecting the PVP based device in series to the gate electrode of the graphene oxide-field effect transistor. The proposed device achieves an extremely low subthreshold swing of 23.7 mV/decade and a high on-off ratio of∼105 due to the steep switching of the threshold switching device at the gate region.

Pneumatic Soft Robots: Challenges and Benefits

In the field of robotics, soft robots have been showing great potential in the areas of medical care, education, service, rescue, exploration, detection, and wearable devices due to their inherently high flexibility, good compliance, excellent adaptability, and natural and safe interactivity. Pneumatic soft robots occupy an essential position among soft robots because of their features such as lightweight, high efficiency, non-pollution, and environmental adaptability. Thanks to its mentioned benefits, increasing research interests have been attracted to the development of novel types of pneumatic soft robots in the last decades. This article aims to investigate the solutions to develop and research the pneumatic soft robot. This paper reviews the status and the main progress of the recent research on pneumatic soft robots. Furthermore, a discussion about the challenges and benefits of the recent advancement of the pneumatic soft robot is provided.

Large-Area and Efficient Sky-Blue Perovskite Light-Emitting Diodes via Blade-Coating.

Large-area fabrication of perovskite light-emitting diodes (PeLEDs) through mass-production techniques has attracted growing attention due to their potential applications in lighting. Several breakthroughs are made for red/infrared and green emissions. Nevertheless, large-area blue/sky-blue PeLEDs, a requisite color for lighting, have not yet been reported. Here, efficient and large-area sky-blue PeLEDs are fabricated through blade-coating supersaturated precursors. The volume ratio of dimethyl sulfoxide to dimethylformamide is tuned to obtain a supersaturated CsPb(Br0.84 Cl0.16 )3 solution. Blade-coating this supersaturated precursor results in nucleation in the solution phase with much higher nucleation sites, and a faster crystallization rate. The uniform films formed by this approach exhibit smaller grain size, lower trap density, and higher radiative recombination rate. The peak external quantum efficiency of the blade-coated PeLEDs reaches 10.3% with sky-blue emission (489nm). Benefitting from the robustness of this blade-coating technique, large-area sky-blue PeLEDs with a device area of 28 cm2 are also achieved with uniform emission. This work represents a significant step forward toward flat-panel lighting and full-color display for the PeLEDs.

A highly flexible form-stable silicone-octadecane PCM composite for heat harvesting

Phase Change Materials (PCM) are efficient materials for thermal management and energy storage due to its high latent heat and recyclability. Many strategies have been employed to form stabilize PCMs through their phase transition; however these materials are almost invariably rigid. Herein a novel flexible form-stable PCM composite was successfully prepared by physical mixing and low temperature curing. They were well characterized in terms of various techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), mechanical and leakage test, etc. A leakage test showed that the composite with 50% octadecane loading was form-stable with only 2.44% leakage. From the differential scanning calorimetry (DSC) results, the octadecane/silicone (Oct/Si) composite was found to possess a latent heat of 103.8 J/g, and an upshift in phase transition temperature was also observed from octadecane's melting point of 30.3 °C to between 34.4 and 37.8 °C, probably due to thermal insulation or microencapsulation by the silicone matrix. Thermogravimetric analysis (TGA) data supported its good thermal stability within this temperature range and mechanical testing of the composites further confirmed its flexibility and durability as evidenced by the Young's Modulus at 388.92 kPa and elongation at 341.42%, making Oct/Si composites useful for application in areas of temperature regulation, cooling, energy harvesting and wearable devices.

Electrooxidation of ethanol and acetaldehyde in neutral electrolyte, an infrared study

• EOR in neutral electrolyte takes place via C1 and C2 pathways. • In situ FTIR reveal the formation of CO adsorbed on the Pt surface at low potentials. • The scission of the C-C bond of ethanol takes place at ca. 300 mv. • Acetic acid is the main reaction product of the EOR or AOR at high potentials. The electrooxidation of ethanol (EOR) in neutral media is attracting a great deal of attention, especially in the area of micro devices and microbial fuel cells. In this work we study the EOR with Pt/C in neutral electrolyte and followed the evolution of the species formed with the potential by in situ FTIR. The EOR in neutral electrolyte displays higher overpotentials than in acid electrolyte but follows a similar reaction pathway, producing mainly C1 species (CO ad , CO 2 ) and C2 species (acetaldehyde, and acetic acid). The scission of the C C bond of ethanol takes place at 200 mV, a potential higher than in acid electrolyte. According to the FTIR experiments, the production of acetaldehyde during the EOR is higher than that of acetic acid. We have also studied the electrooxidation of acetaldehyde (AOR) in a neutral medium with FTIR. We observed the production of CO ad at 300 mV which is oxidized to CO 2 from E ≥ 700 mV.

Improved water repellency and environmental stability of perovskite solar cells by encapsulating with paraffin wax

Hybrid organic-inorganic metal halide perovskite solar cells are the fastest growing cost-effective photovoltaic technology because of their solution processability and lightweight properties. However, the poor stability of perovskite materials in presence of moisture is the main hindrance to their outdoor applications. Here, paraffin wax is explored as an encapsulating material for improving the water repellency of perovskite solar cells. For this purpose, the drop of paraffin from a burning candle is placed on the device area composed of methylammonium lead iodide as a perovskite material and doped poly(3-hexylthiophene) as a hole-transporting layer. The encapsulation does not affect the photovoltaic performance of the tested devices in ambient conditions, exhibiting the same performance as in an inert atmosphere. Moreover, the photovoltaic performance of the encapsulated solar cells remains unchanged even after 2160 h under ambient conditions with continuous exposure to the relative humidity in the range of 70–85%. The encapsulation is so robust that the photovoltaic performance of the cells does not change even after immersing the encapsulated cell in water or after heating at 85 °C. This performance of paraffin coating is superior to many reported sealing agents, which are deposited using costly instruments or by multistep processes. Thus, the paraffin exhibits the potential to be used as an alternative low-cost coating material for perovskite solar cells.

Electron donor or acceptor behavior of a AuCl3 dopant manipulated by dip-pen nanolithography on a MoS2 thin-film transistor

Gold (III) chloride (AuCl3) is a well-known electron acceptor (p-type dopant). Here, the electron donor or acceptor behavior of a AuCl3 dopant on a molybdenum disulfide (MoS2) thin-film transistor (TFT) is demonstrated by line patterning a concentration-adjusted AuCl3 ink with dip-pen nanolithography (DPN). At a low ink concentration (clow) (<3 mM AuCl3), the Au molecules (Au0) are transferred and contact with the MoS2, resulting in an electron donor effect on the MoS2. In contrast, at a high ink concentration (chigh) (≥3 mM), the Au3+ is transferred from the AuCl3 salt loaded on the DPN tip probe and reacts with the MoS2, resulting in an electron acceptor effect. For a clow, the mobility of the MoS2 TFT increases when the Au coverage is larger than 10%. For a chigh, the mobility decreases regardless of the Au coverage. This DPN patterning of the concentration-adjusted AuCl3 inks can be applied to fabricate junction in the local area of MoS2 devices without using complicated lithography. As a result, enhancement of the photoresponse as well as increasing the rectifying behavior of MoS2 devices are demonstrated with the bandgap controlled junction obtained by two direct DPN line patterning operations with the concentration-adjusted AuCl3 inks.

Cover Feature: Quadrupolar Ultrafast Charge Transfer in Diaminoazobenzene‐Bridged Perylenediimide Triads (Chem. Eur. J. 13/2022)

The transfer of charge in covalently linked donor–acceptor systems is highly important in many areas of chemistry, artificial photosynthesis, semiconductor devices, and solar cells. Intramolecular charge transfer occurs when a fraction of the charge is transferred between the entities after photo-excitation of the electron donor or acceptor entity. In this study, molecular triads comprising two electron-deficient perylenediimides are covalently linked to a bridging electron donor, diamino-azobenzene, to give strong ground-state polarization resulting in wide-band optical coverage. Using fluorescence spectro-electrochemistry, charge-transfer reversal in these triads is also seen. Further, the formation of ultrafast quadrupolar charge transfer upon photoexcitation is demonstrated. More information can be found in the Research Article by F. Fernández-Lázaro, F. D′Souza, et al. (DOI: 10.1002/chem.202104574).

The Design and Magnetic Field Analysis of a Double Rotor Permanent Magnet Braking Device

During long-term continuous braking, high-intensity braking, or frequent braking, the temperature of the brake disc or brake drum will increase significantly, resulting in a decrease in the friction coefficient, the aggravation of the wear degree, and the dangerous heat recession of partial or even total loss of braking efficiency. This paper focuses on an innovative double rotor permanent magnet braking device, which is located on the inner side of the wheel hub, to improve the heat decay resistance of the friction braking device. The structure and principle of the double rotor permanent magnet braking device were given, and its main structural parameters were designed, calculated, and optimized. The geometric model and finite element model of the double rotor permanent magnet braking device were established. The static and transient magnetic field analysis and the braking torque characteristic analysis of the double rotor permanent magnet braking device were carried out by using Maxwell electromagnetic analysis software. The results show that the magnetic flux density in the working area of the double rotor permanent magnet braking device increases with the increase in rotation speed, the braking torque changes with the change of rotation speed, and the maximum braking torque occurs in the low-speed area, which is consistent with the theoretical calculation results. This provides a theoretical basis for the follow-up prototype test of the double rotor permanent magnet braking device.

EARLY- STAGE DIABETES PREDICTION USING MACHINE LEARNING CLASSIFICATION ALGORITHMS

Diabetes has developed as one of the maximum risky threats to the human global. Many have become its sufferers and are not able to pop out of it despite the fact that they're running to keep away from it from developing in addition. Cloud Computing and the Internet of Things (IoT) are equipment that play a completely vital function in today’s lifestyles concerning many factors and our poses which includes healthcare tracking of sufferers and aged society. Diabetes Healthcare Monitoring Services may be very vital in recent times due to the fact bodily going to hospitals and status in a queue is a completely useless model of affected person tracking. Maybe if an affected person has very persistent diabetes and it isn’t detected at an early level, his/her ought to spend his/her time in lengthy queues for a prognosis which may be risky if left undetected in an extended run. Diabetes also can act as a way for different sicknesses like coronary heart attack, kidney damage, and relatively blindness. This mission uses numerous devices getting to know algorithms consisting of K-nearest neighbours, naive Bayes, assist vector device(Linear Non-Linear), logistic regression, selection tree, and random wooded area with the assist of which we will without problems discover the accuracy of a version predicting that someone has diabetes or not. Key words: Machine Learning, Classification, Diabetes, Dimensionality Reduction, Analysis Metrics

Tailoring Spectrally Flat Infrared Photodetection with Thickness-Controlled Nanocrystalline Graphite.

Graphene, a zero-gap semiconductor, absorbs 2.3% of incident photons in a wide wavelength range as a free-standing monolayer, whereas 50% is expected for ∼90 layers. Adjusting the layer number allows the tailoring of the photoresponse; however, controlling the thickness of multilayer graphene remains challenging on the wafer scale. Nanocrystalline graphene or graphite (NCG) can instead be grown with controlled thickness. We have fabricated photodetectors from NCG that are spectrally flat in the near-infrared to short-wavelength infrared region by tailoring the layer thicknesses. Transfer matrix simulations were used to determine the NCG thickness for maximum light absorption in the NCG layer on a silicon substrate. The extrinsic and intrinsic photoresponse was determined from 1100 to 2100 nm using chromatic aberration-corrected photocurrent spectroscopy. Diffraction-limited hyperspectral photocurrent imaging shows that the biased photoresponse is unipolar and homogeneous across the device area, whereas the short-circuit photoresponse gives rise to positive and negative photocurrents at the electrodes. The intrinsic photoresponses are wavelength-independent, indicative of bolometric and electrothermal photodetection.

Electrical and Low Frequency Noise Characterization of Graphene Chemical Sensor Devices Having Different Geometries.

Chemiresistive graphene sensors are promising for chemical sensing applications due to their simple device structure, high sensitivity, potential for miniaturization, low-cost, and fast response. In this work, we investigate the effect of (1) ZnO nanoparticle functionalization and (2) engineered defects onto graphene sensing channel on device resistance and low frequency electrical noise. The engineered defects of interest include 2D patterns of squares, stars, and circles and 1D patterns of slots parallel and transverse to the applied electric potential. The goal of this work is to determine which devices are best suited for chemical sensing applications. We find that, relative to pristine graphene devices, nanoparticle functionalization leads to reduced contact resistance but increased sheet resistance. In addition, functionalization lowers 1/f current noise on all but the uniform mesa device and the two devices with graphene strips parallel to carrier transport. The strongest correlations between noise and engineering defects, where normalized noise amplitude as a function of frequency f is described by a model of AN/fγ, are that γ increases with graphene area and contact area but decreases with device total perimeter, including internal features. We did not find evidence of a correlation between the scalar amplitude, AN, and the device channel geometries. In general, for a given device area, the least noise was observed on the least-etched device. These results will lead to an understanding of what features are needed to obtain the optimal device resistance and how to reduce the 1/f noise which will lead to improved sensor performance.

Impact of endocardial leads on the effectiveness of interventional edge-to-edge repair of tricuspid regurgitation

Abstract Funding Acknowledgements Type of funding sources: None. Background A considerable proportion of patients who are considered for percutaneous tricuspid valve edge-to-edge repair (pTVR) interventions have endocardial lead induced tricuspid regurgitation (TR). The aim of this study was to examine the impact of lead-leaflet interaction on the effectiveness of pTVR. Methods For each patient, the lead position within the tricuspid valve (central, commissural, or towards one of the three leaflets) and the type of lead-leaflet interaction (leaflet impingement or adhesion) were identified during thorough 2D/3D transthoracic and transesophageal echocardiography examinations. Before and after pTVR, echocardiographic data, including 3D full-volume datasets, were obtained and quantified. TR severity was graded from 1+ to 5+, based upon the effective regurgitant orifice area by the PISA method (EROAPISA) and the vena contracta area (VCA3D) as measured by multiplanar reconstruction from a 3D color Doppler loop. Maximal diastolic tricuspid annulus area from a 3D zoom image, tricuspid tenting area, and right atrial volume were quantified. Right ventricular assessments included ejection fraction (RVEF3D) and diastolic (RVVd3D) and systolic (RVVs3D) volumes. Results Out of 99 patients who underwent pTVR at our hospital, 38 patients had implanted cardiac devices of the following types: pacemakers (n = 25, 66%), cardiac defibrillators (n = 7, 18%), and biventricular pacemakers (n = 6, 16%). In 24 (63%) of these device patients, TR grade was ≤2+ after pTVR. In 14 of the device patients, TR grade remained severe after intervention (Grade 3+ in 15%, grade 4+ in 11%, and Grade 5+ in 11% of the device group). In comparison, in 78% of patients without endocardial leads, moderate TR was achieved after pTVR. Figure 1 shows the distribution of lead positions within the tricuspid valve. A relevant lead-leaflet interference (rLLI) for pTVR interventions was defined as impingement or adhesion in the target area of the coaptation device (anteroseptal or posteroseptal). Binary logistic regression analysis showed an increase risk (Odds ratio 11, R2 0.34, 95% CI 0.019-0.44, p = 0.003) for a suboptimal pTVR result (TR grade &amp;gt; 2+ after intervention) in patients with rLLI. Although patients with rLLI (n = 17) had significantly higher VCA3D values as compared to patients without rLLI (n = 21), it was not predictive for pTVR results. Echocardiographic parameters of right ventricular and tricuspid valve dimensions showed only a trend to higher values in the group with rLLI (Table 1). Conclusion Endocardial lead induced TR negatively impacts the effectiveness of pTVR irrespective of the initial degree of TR. Abstract Figure. Abstract Table 1 Echocardiographic parameters

Bromine speciation by a paper-based sensor integrated with a citric acid/cysteamine fluorescent probe and smartphone detection

The present work reports on a sensitive and affordable non-instrumental method for the determination of bromine species in environmental waters by combination of paper-based headspace sampling and smartphone-based fluorescence detection. The proposed approach takes advantage of the luminescence quenching of a probe (5-oxo-3,5-dihydro-2 H-thiazolo[3,2-a]pyridine-7-carboxylic acid, TPCA) derived from natural compounds, namely, citric acid and cysteamine, when exposed to molecular bromine. The decreased luminescence intensity of the probe was attributed to the formation of a dibrominated derivative of TPCA at the detection area of a paper-based analytical device (PAD). Remarkably, PADs modified with the luminescent probe showed excellent stability. Under optimal conditions, the proposed approach showed limits of detection of 5.4 µg L-1 and 0.9 µg L-1 for Br- and BrO3-, respectively, with a repeatability lower than 10% for both bromine species. The non-instrumental method was validated against two certified reference materials, namely BCR-611 and BCR-612 (low and high level Br- in groundwater), and successfully applied to the analysis of environmental water samples with recoveries in the range 93–106%.

Enabling high-performance, centimeter-scale organic solar cells through three-dimensional charge transport

Organic solar cells (OSCs) suffer from severe upscaling loss due to the inevitable formation of inhomogeneities and the intrinsically low charge mobilities of organic materials limiting the charge extraction efficiency, especially in the situation where cell width reaches centimeter scale. Here, we report the introduction of a nematic liquid crystal donor, BTR-Cl, into a typical non-fullerene blending system of PM6:BTP-eC9. The participation of BTR-Cl contributes to a significantly improved crystallinity and ordering of the host components and facilitates efficient three-dimensional charge transport in the active layer. Simultaneously improved fill factor and current density are thus achieved in BTR-Cl-doped OSCs, corresponding to a superior efficiency of 18.31%. More importantly, a high efficiency of 16.88% along with a robust fill factor of 73.4% is retained when enlarging the effective device area from 0.034 to 1.01 cm2, highlighting the importance of three-dimensional charge transport in reducing the upscaling loss of OSCs.

Design and Simulation of Normally Off High‐Electron‐Mobility Light‐Emitting Transistor

Herein, a built‐in normally off GaN‐based high‐electron‐mobility light‐emitting transistor is designed and simulated. The proposed structure can significantly minimize the device area, eliminate the parasitic component introduced by metal interconnectors, ensure a fail‐safe operation owing to its normally off operating condition, and it affords fabrication simplicity, a preferable quality for display applications. Using 2D computer‐aided design software (Silvaco's TCAD), the device's electrical and optical features are investigated, revealing good output power linearity and light intensity control by the gate voltage.

Soft-lock drawing of super-aligned carbon nanotube bundles for nanometre electrical contacts.

The assembly of single-walled carbon nanotubes (CNTs) into high-density horizontal arrays is strongly desired for practical applications, but challenges remain despite myriads of research efforts. Herein, we developed a non-destructive soft-lock drawing method to achieve ultraclean single-walled CNT arrays with a very high degree of alignment (angle standard deviation of ~0.03°). These arrays contained a large portion of nanometre-sized CNT bundles, yielding a high packing density (~400 µm-1) and high current carrying capacity (∼1.8 × 108 A cm-2). This alignment strategy can be generally extended to diverse substrates or sources of raw single-walled CNTs. Significantly, the assembled CNT bundles were used as nanometre electrical contacts of high-density monolayer molybdenum disulfide (MoS2) transistors, exhibiting high current density (~38 µA µm-1), low contact resistance (~1.6 kΩ µm), excellent device-to-device uniformity and highly reduced device areas (0.06 µm2 per device), demonstrating their potential for future electronic devices and advanced integration technologies.

Terahertz plasma edge engineering in semiconductor membranes with a two-dimensional electron layer

We have studied the terahertz response of a dielectric membrane with a high-mobility two-dimensional electron system (2DES) on one side. The developed device exhibits electromagnetic transparency above the plasma frequency that is found to be determined by the 2DES density and membrane thickness. Significantly, we demonstrate the opaque low-frequency region to be highly tunable. Our results can find applications in the area of active terahertz devices.

Activated Triplet Exciton Release for Highly Efficient Room-Temperature Phosphorescence Based on S,N-Doped Polymeric Carbon Nitride.

Polymeric carbon nitride (PCN) shows great potential applications in the areas of sustainable energy (photocatalysis and photoelectric conversion, as well as other important catalytic reactions), biosensing, biomedicine, devices, and more, but efficient phosphorescence is very scarce because of the lack of an effective synthetic method and an unsettled phosphorescent mechanism. Herein, we report a strategy to promote efficient phosphorescence to activate triplet exciton release by introduction of S and N elements. PCN could be synthesized by thiourea or urea (named S,N-PCN and N-PCN, respectively) at a relatively low reaction temperature (260 °C). S,N-PCN exhibits phosphorescence quantum yield (4.15%) higher than that (0.41%) for N-PCN. The introduction of C=S and C≡N groups in S,N-PCN networks could boost the intersystem crossing (ISC), leading to small singlet-triplet energy (ΔEST) up to more triplet exciton generation. Considering the excellent optical stability of PCN, a preliminary application of visible-light-excited PCN in advanced anticounterfeiting is proposed.

Modulation of the electrical double layer in metals and conducting polymers

The electrical double layer (EDL) formed at the interface between various materials and an electrolyte has been studied for a long time. In particular, the EDL formed at metal/electrolyte interfaces is central in electrochemistry, with a plethora of applications ranging from corrosion to batteries to sensors. The discovery of highly conductive conjugated polymers has opened a new area of electronics, involving solution-based or solution-interfaced devices, and in particular in bioelectronics, namely for use in deep-brain stimulation electrodes and devices to measure and condition cells activity, as these materials offer new opportunities to interface cells and living tissues. Here, it is shown that the potential associated to the double layer formed at the interface between either metals or conducting polymers and electrolytes is modified by the application of an electric field along the conductive substrate. The EDL acts as a transducer of the electric field applied to the conductive substrate. This observation has profound implications in the modelling and operation of devices relying on interfaces between conductive materials (metals and conjugated polymers) and electrolytes, which encompasses various application fields ranging from medicine to electronics.