Effect of fabrication process on contact resistance and channel in graphene field effect transistors

Contact resistance, as one of the main parameters that limits the performance of graphene-based transistors, is highly dependent on the metal-graphene contact fabrication processes. These processes are investigated and the corresponding resistances are measured based on the transfer length method (TLM). In fabrication processes, when annealing is done on chemical vapor deposition (CVD)-grown graphene samples that are transferred onto SiO2/Si substrates, the adhesion of graphene to the substrate is improved, and poly methyl methacrylate (PMMA) residues are also reduced. When the metal deposition layer is first applied to the graphene, and then, the photolithography process is performed to define the electrodes and graphene sheet, the graphene-metal contact resistance is better than that in other methods due to the removal of photoresist residues. In fact, by changing the sequence of the fabrication process steps, the direct contact between photoresist and graphene surface can be prevented. Thus, the contact resistance is reduced and conductivity increases, and in this way, the performance of graphene transistor improves. The results show that the fabrication process has a noticeable effect on the transistor properties such as contact resistance, channel sheet resistance, and conductivity.‌ Here, by using the annealing process and changing the order of photolithography processes, a contact resistance of 470 Ω μm is obtained for Ni-graphene contact, which is relatively favorable.

Machine learning-powered compact modeling of stochastic electronic devices using mixture density networks

The relentless pursuit of miniaturization and performance enhancement in electronic devices has led to a fundamental challenge in the field of circuit design and simulation-how to accurately account for the inherent stochastic nature of certain devices. While conventional deterministic models have served as indispensable tools for circuit designers, they fall short when it comes to capturing the subtle yet critical variability exhibited by many electronic components. In this paper, we present an innovative approach that transcends the limitations of traditional modeling techniques by harnessing the power of machine learning, specifically Mixture Density Networks (MDNs), to faithfully represent and simulate the stochastic behavior of electronic devices. We demonstrate our approach to model heater cryotrons, where the model is able to capture the stochastic switching dynamics observed in the experiment. Our model shows 0.82% mean absolute error for switching probability. This paper marks a significant step forward in the quest for accurate and versatile compact models, poised to drive innovation in the realm of electronic circuits.

Design of filtering cable with defected conductor layer

Electrical cables, often referred to as 'blood vessels' and 'nerves' of the industry, play a vital role in the connection of electrical devices. However, traditional cables that lack distributed filtering functions are usually the primary coupling path for electromagnetic compatibility (EMC) problems. An innovative design for a filtering cable, which incorporates insulated electrical wires coated with a specific defected conductor layer (DCL), enables it to achieve distributed filtering advantages along its axis. Microwave network analysis is employed to build the two-port network model of filtering cable, which efficiently analyzes the cascading characteristics of periodic or aperiodic filtering cables. To validate, the flexible printed circuit board (FPCB) with sawtooth dumbbell-shaped DCL and mounted by capacitors is wrapped around the stripped section of the coaxial cable to manufacture a multi-stopband filtering cable. Simulated and measured results demonstrate that the proposed filtering cable can be effectively suppressed in the stopband, which can be adjusted by changing the values of capacitors.

Femtosecond electron beam probe of ultrafast electronics

The need for ever-faster information processing requires exceptionally small devices that operate at frequencies approaching the terahertz and petahertz regimes. For the diagnostics of such devices, researchers need a spatiotemporal tool that surpasses the device under test in speed and spatial resolution. Consequently, such a tool cannot be provided by electronics itself. Here we show how ultrafast electron beam probe with terahertz-compressed electron pulses can directly sense local electro-magnetic fields in electronic devices with femtosecond, micrometre and millivolt resolution under normal operation conditions. We analyse the dynamical response of a coplanar waveguide circuit and reveal the impulse response, signal reflections, attenuation and waveguide dispersion directly in the time domain. The demonstrated measurement bandwidth reaches 10 THz and the sensitivity to electric potentials is tens of millivolts or -20 dBm. Femtosecond time resolution and the capability to directly integrate our technique into existing electron-beam inspection devices in semiconductor industry makes our femtosecond electron beam probe a promising tool for research and development of next-generation electronics at unprecedented speed and size.

True pattern-reversal LED stimulator and its comparison to LCD and CRT displays: visual evoked potential study

A rapid checkerboard pattern change is used to elicit pattern-reversal visual evoked potentials (PR VEPs). CRT or LCD monitors do not allow immediate reversal of the entire pattern. The study aimed to construct a new stimulator whose characteristics approximate an instantaneous reversal and verify whether the improvement is reflected in PR VEPs. A new stimulator using a matrix of 12 × 48 independent white square LEDs was designed and compared with LCDs and CRTs. The effect on the PR VEP peak times and amplitudes of N70, P100, and P140 waves was evaluated in ten subjects. The LED stimulator showed significantly better performance in the rate of change of illuminance, change of pattern, luminance settling and stability. The PR VEP amplitudes of N75, P100, and N140 did not show significant differences. The sum of interpeak amplitudes was significantly larger for the LCD than for the other monitors. The peak times of the waves evoked by the LED were shorter than those evoked by the LCD and CRT for the N75 wave and a check size of 30´. LED stimulators are a better alternative to CRTs for PR VEPs than current LCDs. LEDs also seem to be better than CRTs, but further research is necessary to obtain significant results.

An efficient and accurate semi-analytical matching technique for waveguide-fed antennas

Several RF and microwave radiating devices, such as horn antennas, Fabry-Perot cavity antennas, and aperture-fed focusing devices, are excited through rectangular waveguides. The impedance matching of the overall system (from the waveguide feed to the radiating aperture) is a task of crucial importance that is often addressed by means of brute-force parameter-sweep full-wave analyses or blind optimization algorithms. In both cases, a significant amount of memory and time resources are required. For this purpose, we propose here a simple, yet effective solution, which only requires a single full-wave simulation and a semi-analytical procedure. The former is used to retrieve the antenna input impedance at the end of the waveguide port excitation. The semi-analytical procedure consists in a transmission-line equivalent circuit that models two waveguide discontinuities (namely two capacitive irises) within the waveguide section, whose position and geometric features are finely tuned to obtain a satisfactory impedance matching around the working frequency. The proposed method is shown to be effective in diverse and attractive application-oriented contexts, from the impedance matching of a Fabry-Perot cavity antenna to that of a wireless near-field link between two aperture-fed focusing devices. A remarkable agreement between full-wave simulations and numerical results is found in all cases. Thanks to its versatility, simplicity, and a rather low demand of computational resources, the proposed approach may become an essential tool for the effective design of waveguide-fed antennas.

A Wilkinson power divider with harmonic suppression through low-pass filter for GSM and LTE applications

Conventional Wilkinson power dividers (WPDs) perform satisfactorily near the intended operation frequency. Nonetheless, these WPDs demonstrate subpar performance in the stopband and necessitate a significant physical space. To enhance the existing level of advancement and in order to improve on the current state-of-the-art, a modified WPD is designed and fabricated, demonstrating a significant improvement in stopband and superior isolation between output ports. To improve the stopband and suppress unwanted harmonics, a low-pass filter (LPF) structure is placed in the both branches of the conventional WPD. The proposed modified WPD depicts a wide stopband bandwidth (fSB > 17.25 GHz) from 2.75 to over 20 GHz with an attenuation level of 20 dB, suppressing 2nd to 11th harmonics. According to measured results, the input return loss (|S11|), insertion loss (|S21|) and output isolation (|S32|) at f = 1.8 GHz are better than 33 dB, 3.2 dB and 21 dB, respectively. Indeed, the proposed modified WPD exhibits a magnitude imbalance of 0.00018, a phase imbalance of 1.25 degrees and a group delay of 0.5 ns. The proposed WPD depicts a compact size of 35 mm × 25 mm (0.38 λg × 0.27 λg), where λg is the guided wavelength at f = 1.8 GHz. There is a good agreement between the simulated and measured results. According to the obtained results, the proposed modified WPD shows a desirable performance for modern LTE and GSM communication applications.

High-performance hydrogen gas sensor system based on transparent coaxial cylinder capacitive electrodes and a volumetric analysis technique

A high-performance H2 gas sensor system based on capacitive electrodes and a volumetric analysis technique were developed. Coaxial capacitive electrodes were fabricated by placing a thin copper rod in the center and by adhering a transparent conductive film on the exterior surface of a graduated cylinder. Thus, H2 from a polymer specimen lowered the water level in the cylinder between the two electrodes, producing measurable changes in capacitance that allowed for the measurement of the H2 concentration emitted from the specimen enriched by H2 under high-pressure conditions. The sensing system detected diffused/permeated hydrogen gas from a specimen and hydrogen gas leaks caused by imperfect sealing. The hydrogen gas sensor responded almost instantly at 1 s and measured hydrogen concentrations ranging from 0.15 to 1500 ppm with controllable sensitivity and a measurable range. In addition, performance tests with polymer specimens used in hydrogen infrastructure verified that the sensor system was reliable; additionally, it had a broad measurement range to four decimal places. The sensor system developed in this study could be applied to detect and characterize pure gases (He, N2, O2 and Ar) by real time measurement.

High-performance p-type V2O3 films by spray pyrolysis for transparent conducting oxide applications

High-quality epitaxial p-type V2O3 thin films have been synthesized by spray pyrolysis. The films exhibited excellent electrical performance, with measurable mobility and high carrier concentration. The conductivity of the films varied between 115 and 1079 Scm-1 while the optical transparency of the films ranged from 32 to 65% in the visible region. The observed limitations in thinner films' mobility were attributed to the nanosized granular structure and the presence of two preferred growth orientations. The 60 nm thick V2O3 film demonstrated a highly competitive transparency-conductivity figure of merit compared to the state-of-the-art.

Differential perovskite hemispherical photodetector for intelligent imaging and location tracking

Advanced photodetectors with intelligent functions are expected to take an important role in future technology. However, completing complex detection tasks within a limited number of pixels is still challenging. Here, we report a differential perovskite hemispherical photodetector serving as a smart locator for intelligent imaging and location tracking. The high external quantum efficiency (~1000%) and low noise (10-13 A Hz-0.5) of perovskite hemispherical photodetector enable stable and large variations in signal response. Analysing the differential light response of only 8 pixels with the computer algorithm can realize the capability of colorful imaging and a computational spectral resolution of 4.7 nm in a low-cost and lensless device geometry. Through machine learning to mimic the differential current signal under different applied biases, one more dimensional detection information can be recorded, for dynamically tracking the running trajectory of an object in a three-dimensional space or two-dimensional plane with a color classification function.

Exploration of a wide bandgap semiconducting supramolecular Mg(II)-metallohydrogel derived from an aliphatic amine: a robust resistive switching framework for brain-inspired computing

A rapid metallohydrogelation strategy has been developed of magnesium(II)-ion using trimethylamine as a low molecular weight gelator in water medium at room temperature. The mechanical property of the synthesized metallohydrogel material is established through the rheological analysis. The nano-rose like morphological patterns of Mg(II)-metallohydrogel are characterized through field emission scanning electron microscopic study. The energy dispersive X-ray elemental mapping analysis confirms the primary gel forming elements of Mg(II)-metallohydrogel. The possible metallohydrogel formation strategy has been analyzed through FT-IR spectroscopic study. In this work, magnesium(II) metallohydrogel (Mg@TMA) based metal-semiconductor-metal structures have been developed and charge transport behaviour is studied. Here, it is confirmed that the magnesium(II) metallohydrogel (Mg@TMA) based resistive random access memory (RRAM) device is showing bipolar resistive switching behaviour at room temperature. We have also explored the mechanism of resistive switching behaviour using the formation (rupture) of conductive filaments between the metal electrodes. This RRAM devices exhibit excellent switching endurance over 10,000 switching cycles with a large ON/OFF ratio (~ 100). The easy fabrication techniques, robust resistive switching behaviour and stability of the present system makes these structures preferred candidate for applications in non-volatile memory design, neuromorphic computing, flexible electronics and optoelectronics etc.

Superconducting transition edge bolometer for high-flux neutron detection

Needs for neutron detection and monitoring in high neutron flux environments are increasing in several different fields. A completely solid-state, current mode bolometric detector is constructed as a solid substrate transition edge sensor based on a high-T[Formula: see text] superconducting meander. The detector consists of four individual pixels of which three pixels include [Formula: see text] neutron absorption layers. The absorbed energy per neutron absorption reaction is modelled and compared to experimental data. The response of the tested detector is directly correlated to a cold neutron beam with a flux of [Formula: see text] modulated by a slit. The signal is found to be an order of magnitude higher than the thermal background. The dynamics described by the temporal saturation constants is governed by a modulation frequency less than [Formula: see text]. The thermal response is dynamic and never fully saturates for [Formula: see text] exposures. The efficiency for this proof-of-principle design is 1-2%. Possibilities for optimization are identified, that will increase the efficiency to become comparable to existing solid boron-10 detectors. The existing detectors with event-based read-out have limited functionality in high flux environments. The superconducting bolometer described in this work using current-mode readout will pave the way for high flux applications.

Pulse-controlled qubit in semiconductor double quantum dots

We present a numerically-optimized multipulse framework for the quantum control of a single-electron double quantum dot qubit. Our framework defines a set of pulse sequences, necessary for the manipulation of the ideal qubit basis, that avoids errors associated with excitations outside the computational subspace. A novel control scheme manipulates the qubit adiabatically, while also retaining high speed and ability to perform a general single-qubit rotation. This basis generates spatially localized logical qubit states, making readout straightforward. We consider experimentally realistic semiconductor qubits with finite pulse rise and fall times and determine the fastest pulse sequence yielding the highest fidelity. We show that our protocol leads to improved control of a qubit. We present simulations of a double quantum dot in a semiconductor device to visualize and verify our protocol. These results can be generalized to other physical systems since they depend only on pulse rise and fall times and the energy gap between the two lowest eigenstates.

Enhancing supercapacitor performance through design optimization of laser-induced graphene and MWCNT coatings for flexible and portable energy storage

The field of supercapacitors consistently focuses on research and challenges to improve energy efficiency, capacitance, flexibility, and stability. Low-cost laser-induced graphene (LIG) offers a promising alternative to commercially available graphene for next-generation wearable and portable devices, thanks to its remarkable specific surface area, excellent mechanical flexibility, and exceptional electrical properties. We report on the development of LIG-based flexible supercapacitors with optimized geometries, which demonstrate high capacitance and energy density while maintaining flexibility and stability. Three-dimensional porous graphene films were synthesized, and devices with optimized parameters were fabricated and tested. One type of device utilized LIG, while two other types were fabricated on LIG by coating multi-walled carbon nanotubes (MWCNT) at varying concentrations. Characterization techniques, including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and voltammetry, were employed to analyze the fabricated devices. AFM analysis revealed a surface roughness of 2.03 µm for LIG due to laser treatment. SEM images displayed compact, dense, and porous surface morphology. XRD analysis confirmed the presence of graphene and graphene oxide, which was further supported by energy-dispersive X-ray spectroscopy (EDX) data. Raman spectroscopy indicated that the fabricated samples exhibited distinct D and G bands at 1362 cm-1 and 1579 cm-1, respectively. Cyclic voltammetry (CV) results showed that LIG's capacitance, power density, and energy density were 6.09 mF cm-2, 0.199 mW cm-2, and 3.38 µWh cm-2, respectively, at a current density of 0.2 mA cm-2. The LIG-MWCNT coated electrode exhibited a higher energy density of 6.05 µWh cm-2 and an areal-specific capacitance of 51.975 mF cm-2 compared to the LIG-based devices. The fabricated device has potential applications in smart electronics, nanorobotics, microelectromechanical systems (MEMS), and wearable and portable electronics.

A novel SIGGW dual post band-pass filter for 5G millimeter-wave band applications with a transmission zero

Integration of planar circuits been considered a credible technique for low-cost mass production of microwave and millimeter-wave circuits and systems. For the first time, in this research a dual-post band-pass filter is designed and simulated in a three-layer substrate integrated gap groove waveguide (SIGGW) for 5G millimeter-wave frequency band applications. The filter includes 12 posts ([Formula: see text]). Also, the structure facilitates to use resonant posts and so we can design the posts to add a transmission zero in lower rejection band. The design theory algorithm and its limitations are investigated based on the circuit model of filter. The results shows that FBW of 5% and a lower band transmission zero for the proposed 12 posts filter. Also, the results are verified by simulation using CST. According to the results, the proposed filter is a good option for Ka-band applications and can be used as the building block for suppressing the LO leakage that is commonly used for up-converting the 5G signal to Ka band.

Selection of metallic liquid in sub-6 GHz antenna design for 6G networks

The rapid evolution of wireless communication systems toward 6G demands efficient antennas with the features of adaptability and versatility. Liquid antennas have gained significant research interest due to their unique features in realizing small, flexible, transparent, and reconfigurable antennas for promising applications in future wireless systems. In this paper, in order to find a suitable metallic liquid for effective antennas, we design and compare the performance of metallic liquid antennas using Mercury, gallium indium alloy (EGaIn), and Graphene metallic liquid in the sub-6 GHz frequency. The antenna is realized by the metallic liquid in a poly methyl methacrylate microfluidic channel over a liquid crystal polymer substrate at 5.6 GHz frequency. The performance of these metallic liquid antennas is analyzed by their electromagnetic and radiation performance. The Graphene-based metallic liquid antenna shows better electromagnetic performance in comparison to Mercury and EGaIn metallic liquid antennas.

Engineering electrode interfaces for telecom-band photodetection in MoS2/Au heterostructures via sub-band light absorption

Transition metal dichalcogenide (TMD) layered semiconductors possess immense potential in the design of photonic, electronic, optoelectronic, and sensor devices. However, the sub-bandgap light absorption of TMD in the range from near-infrared (NIR) to short-wavelength infrared (SWIR) is insufficient for applications beyond the bandgap limit. Herein, we report that the sub-bandgap photoresponse of MoS2/Au heterostructures can be robustly modulated by the electrode fabrication method employed. We observed up to 60% sub-bandgap absorption in the MoS2/Au heterostructure, which includes the hybridized interface, where the Au layer was applied via sputter deposition. The greatly enhanced absorption of sub-bandgap light is due to the planar cavity formed by MoS2 and Au; as such, the absorption spectrum can be tuned by altering the thickness of the MoS2 layer. Photocurrent in the SWIR wavelength range increases due to increased absorption, which means that broad wavelength detection from visible toward SWIR is possible. We also achieved rapid photoresponse (~150 µs) and high responsivity (17 mA W-1) at an excitation wavelength of 1550 nm. Our findings demonstrate a facile method for optical property modulation using metal electrode engineering and for realizing SWIR photodetection in wide-bandgap 2D materials.

A new large area MCP-PMT for high energy detection

20-inch Large area photomultiplier tube based on microchannel plate (MCP-PMT) is newly developed in China. It is widely used in high energy detection experiments such as Jiangmen Underground Neutrino Observatory (JUNO), China JinPing underground Laboratory (CJPL) and Large High Altitude Air Shower Observatory (LHAASO). To overcome the poor time performance of the existing MCP-PMT, a new design of large area MCP-PMT is proposed in this paper. Three-dimensional models are developed in CST Studio Suite to validate its feasibility. Effects of the size and bias voltage of the focusing electrodes and MCP configuration on the collection efficiency (CE) and time performance are studied in detail using the finite integral technique and Monte Carlo method. Based on the simulation results, the optimized operating and geometry parameters are chosen. Results show that the mean ratio of photoelectrons landing on the MCP active area is 97.5%. The acceptance fraction of the impinging photoelectrons is close to 100% due to the emission of multiple secondary electrons when hitting the MCP top surface. The mean transit time spread (TTS) of the photoelectrons from the photocathode is 1.48 ns.

Field emission in vacuum resonant tunneling heterostructures with high current densities

We analyse the steady-state thermal regime of a one-dimensional triode resonant tunnelling structure. The high currents generated by resonant tunnelling produce a large amount of heat that could damage the structure. Establishing the conditions under which it can operate at optimum efficiency is therefore a problem of great relevance for applications. The tunnel current is found via eigenvalues of the Schrödinger equation in quantum wells. By calculating the current generated in the device and using the energy conservation law in the electrodes, the temperature reached is obtained for different types of electrodes and the importance of heat conduction and thermal radiation is analysed. In the cases discussed, conduction is dominant. When the electrode material is copper, the temperature reached is similar to that of the thermostat for a wide range of electrode lengths, whereas when the cathode material is diamond-graphite and the anode material is copper, the temperature increases significantly as a function of length. The results obtained allow the temperature to be controlled for optimum performance of the field-emitting triode structures.

Lifetime enhancement in QDLEDs via an electron-blocking hole transport layer

This study investigates the impact of an engineered hole transport layer (HTL) on the stability of electroluminescent quantum dot light-emitting devices (QDLEDs). The 9-Phenyl-3,6-bis(9-phenyl-9Hcarbazol-3-yl)-9H-carbazole (Tris-PCz) HTL, which possesses a shallower lowest unoccupied molecular orbital (LUMO) energy level compared to the widely used 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP) HTL, is employed to confine electron overflow toward the HTL. Utilizing the Tris-PCz HTL results in a 20× improvement in the electroluminescence half-life (LT50) of QDLEDs compared with conventional QDLEDs using the CBP HTL. Electric and optoelectronic analyses reveal that the migration of excess electrons toward the HTL is impeded by the up-shifted LUMO level of Tris-PCz, contributing to prolonged operational device stability. Furthermore, the augmented electric field at the QD/Tris-PCz interface, due to accumulated electrons, expedites hole injection rates, leading to better charge injection balance and the confinement of the exciton recombination zone within the QD and thus the device stability enhancement. This study highlights the significant influence of the HTL on QDLED stability and represents one of the longest LT50 for a QDLED based on the conventional core/shell QD structure.

An S-band multimode reflector antenna for a satellite constellation tracking system

A multimode reflector antenna is a new concept proposed by our team in recent years, which does not correspond to the use of the traditional multimode feed but to innovation in the reflector design. This paper presents an S-band multimode reflector antenna based on multimode reflector theory. To achieve a flat-top beam shape, the main reflector of the antenna is divided into a middle region and an edge region. The height difference between them is approximately λ0/4, and then, the reflected waves in different areas partially cancel out in the direction of maximum radiation. The voltage standing wave ratio of the antenna is less than 1.5 from 2.8 to 3.4 GHz (19.4%), and the gain is more than 29.2 dB in the same frequency band. At the same time, a good flat-top beam is achieved in the range of ± 2°. The antenna can be used for satellite constellation tracking and other systems that require high-gain flat-top beams.

Chemically-stable flexible transparent electrode: gold-electrodeposited on embedded silver nanowires

Silver nanowires (AgNWs) with a low diameter, high aspect ratio, stable suspension, and easy synthesis have recently attracted the optoelectronic industry as a low-cost alternative to indium tin oxide transparent conductive films. However, silver nanowires are not chemically stable, and their conductivity diminishes over time due to reactions with atmospheric components. This is a bottleneck for their wide industrial applications. In this study, we aim to address this issue by synthesizing silver nanowires with an average diameter of approximately 65 nm and a length of approximately 13 µm. The prepared Ag nanowires are then applied to fabricate transparent, flexible, and chemically stable conductive films. The fabrication includes spraying of silver nanowires suspension on a glass substrate followed by Dr. blade coating of polystyrene (PS) solution and delamination of the PS-AgNWs film. The resulting film exhibits an optimum sheet resistance of 24 Ω/□ and transmittance of 84%. To further enhance the stability of the transparent conductive film, the facial and scalable double pulse electrodeposition method is used for coating of gold on the exposed surface of the AgNWs embedded in PS. The final transparent film with gold coating demonstrates a remarkable stability under harsh conditions including long exposure to UV light and nitric acid solution. After 100 min of UV/Ozone treatment, the increase in sheet resistance of the optimal PS-AgNW@Au sample is 15.6 times lower than the samples without gold coating. In addition, the change in sheet resistance after 2000 bending cycles in the optimal PS-AgNW@Au electrode is measured and it showed an increase of only 22% of its initial sheet resistance indicating its good flexibility. The proposed electrode performs an excellent chemical stability, good conductivity, transparency, and flexibility that makes it a potential candidate for various optoelectronic devices.

Effect of electrode materials on resistive switching behaviour of NbOx-based memristive devices

Memristive devices that rely on redox-based resistive switching mechanism have attracted great attention for the development of next-generation memory and computing architectures. However, a detailed understanding of the relationship between involved materials, interfaces, and device functionalities still represents a challenge. In this work, we analyse the effect of electrode metals on resistive switching functionalities of NbOx-based memristive cells. For this purpose, the effect of Au, Pt, Ir, TiN, and Nb top electrodes was investigated in devices based on amorphous NbOx grown by anodic oxidation on a Nb substrate exploited also as counter electrode. It is shown that the choice of the metal electrode regulates electronic transport properties of metal-insulator interfaces, strongly influences the electroforming process, and the following resistive switching characteristics. Results show that the electronic blocking character of Schottky interfaces provided by Au and Pt metal electrodes results in better resistive switching performances. It is shown that Pt represents the best choice for the realization of memristive cells when the NbOx thickness is reduced, making possible the realization of memristive cells characterised by low variability in operating voltages, resistance states and with low device-to-device variability. These results can provide new insights towards a rational design of redox-based memristive cells.

Effect of sub-pixel multiplexing on the display quality of LED display

In this paper, a theoretical model is presented for the display process of uniformly-arranged virtual-pixel LED displays with RGBG sub-pixel structure cells. Such displays' modulation transfer function (MTF) is derived theoretically from this model. Experiments were conducted to validate the theoretical model to measure the MTF of virtual-pixel displays and traditional real-pixel displays with a pixel pitch of 0.9 mm. A dual-line spread function measurement method is proposed, which is experimentally shown to be more effective than the conventional single-line LSF measurement method in measuring the MTF of LED displays. The rationality of the theoretical model was analyzed and compared through experiments. Furthermore, a combined subjective and objective evaluation method for the image quality of LED sub-pixel displays is proposed, which analyses the effect of LED sub-pixel multiplexing on the display clarity based on the square root integration method and achieves the subjective goal of quantifying the LED display quality. The research results reveal the theoretical and experimental aspects of virtual-pixel displays and may have practical significance for the design of high-quality LED displays.

Addressable superconductor integrated circuit memory from delay lines

Recent advances in logic schemes and fabrication processes have renewed interest in using superconductor electronics for energy-efficient computing and quantum control processors. However, scalable superconducting memory still poses a challenge. To address this issue, we present an alternative to approaches that solely emphasize storage cell miniaturization by exploiting the minimal attenuation and dispersion properties of superconducting passive transmission lines to develop a delay-line memory system. This fully superconducting design operates at speeds between 20 and 100 GHz, with ± 24% and ± 13% bias margins, respectively, and demonstrates data densities in the 10s of Mbit/cm2 with the MIT Lincoln Laboratory SC2 fabrication process. Additionally, the circulating nature of this design allows for minimal control circuitry, eliminates the need for data splitting and merging, and enables inexpensive implementations of sequential access and content-addressable memories. Further advances in fabrication processes suggest data densities of 100s of Mbit/cm2 and beyond.

Highly sensitive label-free biosensor: graphene/CaF2 multilayer for gas, cancer, virus, and diabetes detection with enhanced quality factor and figure of merit

One of the primary goals for the researchers is to create a high-quality sensor with a simple structure because of the urgent requirement to identify biomolecules at low concentrations to diagnose diseases and detect hazardous chemicals for health early on. Recently graphene has attracted much interest in the field of improved biosensors. Meanwhile, graphene with new materials such as CaF2 has been widely used to improve the applications of graphene-based sensors. Using the fantastic features of the graphene/CaF2 multilayer, this article proposes an improvement sensor in the sensitivity (S), the figure of merit (FOM), and the quality factor (Q). The proposed sensor is based on the five-layers graphene/dielectric grating integrated with a Fabry-Perot cavity. By tuning graphene chemical potential (µc), due to the semi-metal features of graphene, the surface plasmon resonance (SPR) waves excited at the graphene/dielectric boundaries. Due to the vertical polarization of the source to the gratings and the symmetry of the electric field, both corners of the grating act as electric dipoles, and this causes the propagation of plasmonic waves on the graphene surface to propagate towards each other. Finally, it causes Fabry-Perot (FP) interference on the surface of graphene in the proposed structure's active medium (the area where the sample is located). In this article, using the inherent nature of FP interference and its S to the environment's refractive index (RI), by changing a minimal amount in the RI of the sample, the resonance wavelength (interferometer order) shifts sharply. The proposed design can detect and sense some cancers, such as Adrenal Gland Cancer, Blood Cancer, Breast Cancer I, Breast Cancer II, Cervical Cancer, and skin cancer precisely. By optimizing the structure, we can achieve an S as high as 9000 nm/RIU and a FOM of about 52.14 for the first resonance order (M1). Likewise, the remarkable S of 38,000 nm/RIU and the FOM of 81 have been obtained for the second mode (M2). In addition, the proposed label-free SPR sensor can detect changes in the concentration of various materials, including gases and biomolecules, hemoglobin, breast cancer, diabetes, leukemia, and most alloys, with an accuracy of 0.001. The proposed sensor can sense urine concentration with a maximum S of 8500 nm/RIU and cancers with high S in the 6000 nm/RIU range to 7000 nm/RIU. Also, four viruses, such as M13 bacteriophage, HIV type one, Herpes simplex type 1, and influenza, have been investigated, showing Maximum S (for second resonance mode of λR(M2) of 8000 nm/RIU (λR(M2) = 11.2 µm), 12,000 nm/RIU (λR(M2) = 10.73 µm), 38,000 nm/RIU (λR(M2) = 11.78 µm), and 12,000 nm/RIU (λR(M2) = 10.6 µm), respectively, and the obtained S for first resonance mode (λR(M1)) for mentioned viruses are 4740 nm/RIU (λR(M1) = 8.7 µm), 8010 nm/RIU (λR(M1) = 8.44 µm), 8100 nm/RIU (λR(M1) = 10.15 µm), and 9000 (λR(M1) = 8.36 µm), respectively.

Tapered high-gain Fabry-Perot cavity antenna with high sidelobe suppression for 5G industry

We propose a Fabry-Perot cavity (FPC) antenna to suppress a sidelobe level (SLL) while maintaining a reasonably high gain. Generally, conventional FPC antennas (FPCAs) produce a high SLL because waves in their FPC leak considerably through lateral openings, which is a primary reason for lowering antenna gains. We propose two design approaches to solve this problem: the reflection magnitude tapering of a partially reflective surface (PRS) and considering different incident modes for the PRS design. First, the proposed tapering can remarkably reduce an SLL by providing the PRS with more radiation opportunities. Second, the different incident modes of transverse electric (TE) and transverse magnetic (TM) can increase an antenna gain by considering a more realistic illumination environment of the PRS. We have proven that our antenna provides 19.8 dBi realized gain with high sidelobe suppression (SLS) of more than 23 dB. Consequently, the proposed FPCA can suppress sidelobes significantly while maintaining a high gain. Good agreement between simulations and experiments demonstrates the usefulness of our proposal.

Design and characterization of mesoscopic dielectric cuboid antenna for operation in WR-3.4 waveguide bandwidth (220-330 GHz)

We designed a mesoscopic dielectric cuboid antenna connected to a flangeless WR-3.4 open-ended waveguide, and the antenna characteristics at 300 GHz were examined through simulations and experiments. Simulations confirmed that the flangeless design eliminated the flange-induced ripples in the radiation pattern, whose shape varied with frequency, and that the antenna operated in the full bandwidth of the WR-3.4 waveguide (220-330 GHz). Prototypes were then fabricated based on the simulation findings. A prototype with an antenna aperture area of 1.5 mm [Formula: see text] 1.5 mm and an antenna length of 2.35 mm exhibited an antenna gain of 17.2 dBi at 300 GHz and a voltage standing wave ratio of less than 1.5 throughout the WR-3.4 waveguide bandwidth. The level of the side lobes at about [Formula: see text] degrees in the E-plane pattern was approximately [Formula: see text] dB that of the main lobe. Therefore, the proposed antenna, connected to a flangeless waveguide, is a promising antenna for use in future short-range high-speed terahertz wireless applications such as kiosk downloads and board-to-board communication.

Computationally-efficient statistical design and yield optimization of resonator-based notch filters using feature-based surrogates

Modern microwave devices are designed to fulfill stringent requirements pertaining to electrical performance, which requires, among others, a meticulous tuning of their geometry parameters. When moving up in frequency, physical dimensions of passive microwave circuits become smaller, making the system performance increasingly susceptible to manufacturing tolerances. In particular, inherent inaccuracy of fabrication processes affect the fundamental operating parameters, such as center frequency or bandwidth, which is especially troublesome for narrow-band structures, including notch filters. The ability to quantify the effects of tolerances, and-even more-to account for these in the design process, are instrumental in making the designs more reliable, and to increase the likelihood that adequate operation is ensured despite manufacturing errors. This paper proposes a simple yet computationally efficient and reliable procedure for statistical analysis and yield optimization of resonator-based notch filters. Our methodology involves feature-based surrogate models that can be established using a handful of training data points, and employed for rapid evaluation of the circuit fabrication yield. Furthermore, a yield optimization procedure is developed, which iteratively sets up a sequence of feature-based models, constructed within local domains relocated along the optimization path, and uses them as predictors to find a robust (maximum yield) design at a low computational cost. The presented approach has been demonstrated using two complementary split ring resonator (CSRR)-based notch filters. The cost of statistical design is about a hundred of EM simulations of the respective filter, with yield evaluation reliability corroborated through EM-based Monte Carlo analysis.

Real-time mode of operation data analysis to catch the thread-tip denotes the failure cause of the grid-tie PV central inverter

The inverter is considered the core of the PV power plant. The inverter's failure leads to generation loss and decreases plant availability. So, it is required to investigate a clear Root Cause Analysis (RCA) to deduce the failure causes and implement the required corrective action in addition to the preventive action to avoid more inverter failure, hereby maintaining the plant available to a certain value. This paper discusses real-time mode operation data analysis of the PV grid-connected inverter due to real central inverter incidents in Benban solar park located in Egypt.The central inverter plays an important role in the Mega-Scale PV power plant. The main function of this inverter is to convert the DC power produced by the PV modules to AC power to be injected into the utility grid by considering specific characteristics based on the grid code. The availability of any PV power plant directly depends on the healthy inverter's operation. The more increases for the installed inverters, the less availability loss in the case of inverter partial or catastrophic failures. So, it is required to focus on the failure causes of the central inverter by implementing a technical analysis using the available operational data. The monitored data of the central inverter in the PV power plant is classified into two types. The first type is the continuous time data stored in the memory. It represents the waveforms of inverter outputs like voltage, current, frequency, …. etc. Unfortunately, in case of a catastrophic failure, the central inverter is completely charred, and the continuous time data is lost due to storage memory damage. The second type is the operation data that is recorded by the SCADA system (per one-minute interval). Hereby, the operation data is the sole data in the case of the completely charred inverter. The representation of the operational data in curves indicates symptoms that can be used for the RCA processes. The investigation outcomes include three results. The first result is detecting the signature of the IGBT thermal stress on the voltage balance of the DC link capacitor. The second result is verifying a scenario for the cause of the IGBT failure by implementing a technical mathematical model based on the detected symptoms that denote the fault signature which is considered the thread-tip for detecting the failure cause. The third result is the simulating scenario for the interpretation of a DC link capacitors explosion due to the short circuit fault that occurred due to IGBT failure. The investigation in this paper is performed based on operation data analysis of the PV grid-connected inverter (central type) due to a real incident. The analysis methodology is based on mathematical calculation for the IGBT junction temperature using the measured heatsink temperature. The study concludes that after the IGBT failure occurred, it was a short circuit for a while and closed the terminals of the DC link capacitors. So, the DC link capacitors exploded and produced heavy sparks that led to enough fire to burn the inverter container completely.

Noise resilient exceptional-point voltmeters enabled by oscillation quenching phenomena

Exceptional point degeneracies (EPD) of linear non-Hermitian systems have been recently utilized for hypersensitive sensing. This proposal exploits the sublinear response that the degenerate frequencies experience once the system is externally perturbed. The enhanced sensitivity, however, might be offset by excess (fundamental and/or technical) noise. Here, we developed a self-oscillating nonlinear platform that supports transitions between two distinct oscillation quenching mechanisms - one having a spatially symmetric steady-state, and the other with an asymmetric steady-state - and displays nonlinear EPDs (NLEPDs) that can be employed for noise-resilient sensing. The experimental setup incorporates a nonlinear electronic dimer with voltage-sensitive coupling and demonstrates two-orders signal-to-noise enhancement of voltage variation measurements near NLEPDs. Our results resolve a long-standing debate on the efficacy of EPD-sensing in active systems above self-oscillating threshold.

Thermalization and relaxation mediated by phonon management in tin-lead perovskites

Understanding and control of ultrafast non-equilibrium processes in semiconductors is key to making use of the full photon energy before relaxation, leading to new ways to break efficiency limits for solar energy conversion. In this work, we demonstrate the observation and modulation of slow relaxation in uniformly mixed tin-lead perovskites (MASnxPb1-xI3 and CsSnxPb1-xI3 nanocrystals). Transient absorption measurements reveal that slow cooling mediated by a hot phonon bottleneck effect appears at carrier densities above ~1018 cm-3 for tin-lead alloy nanocrystals, and tin addition is found to give rise to suppressed cooling. Within the alloy nanoparticles, the combination of a newly introduced high-energy band, screened Fröhlich interaction, suppressed Klemens decay and reduced thermal conductivity (acoustic phonon transport) with increased tin content contributes to the slowed relaxation. For inorganic nanocrystals where defect states couple strongly with carriers, sodium doping has been confirmed to benefit in maintaining hot carriers by decoupling them from deep defects, leading to a decreased energy-loss rate during thermalization and an enhanced hot phonon bottleneck effect. The slow cooling we observe uncovers the intrinsic photophysics of perovskite nanocrystals, with implications for photovoltaic applications where suppressed cooling could lead to hot-carrier solar cells.

Machine learning approach for predicting electrical features of Schottky structures with graphene and ZnTiO3 nanostructures doped in PVP interfacial layer

In this research, for some different Schottky type structures with and without a nanocomposite interfacial layer, the current-voltage (I-V) characteristics have been investigated by using different Machine Learning (ML) algorithms to predict and analyze the structures' principal electric parameters such as leakage current (I0), barrier height ([Formula: see text]), ideality factor (n), series resistance (Rs), shunt resistance (Rsh), rectifying ratio (RR), and interface states density (Nss). The interfacial nanocomposite layer is made by composing polyvinyl-pyrrolidone (PVP), zinc titanate (ZnTiO3), and graphene (Gr) nanostructures. The Gaussian Process Regression (GPR), Kernel Ridge Regression (KRR), Support Vector Regression (SVR), and Artificial Neural Network (ANN) are used as ML algorithms. The ML techniques training data are obtained using the thermionic emission method. Finally, by comparing the experimental and predicted results, the performance of the different ML algorithms in predicting the electrical parameters of Schottky diodes (SDs) has been compared to find the optimized ML algorithm. The ML predictions of basic electrical parameters by almost all algorithms are in good agreement with the actual values, while the SVR model has predicted closer values to the corresponding actual ones. The obtained results show that the quantity of the leakage current and Nss for MS type SD decreases, and φB0 increases with the interfacial layer usage, especially with graphene dopant.

Electrical analogue of one-dimensional and quasi-one-dimensional Aubry-André-Harper lattices

This work explores the potential for achieving correlated disorder in electrical circuits by utilizing reactive elements. By establishing a direct correspondence between the tight-binding Hamiltonian and the admittance matrix of the circuit, a novel approach is presented. The localization phenomena within the circuit are investigated through the analysis of the two-port impedance. To introduce correlated disorder, the Aubry-André-Harper (AAH) model is employed. Both one-dimensional and quasi-one-dimensional AAH structures are examined and effectively mapped to their tight-binding counterparts. Notably, transitions from a high-conducting phase to a low-conducting phase are observed in these circuits, highlighting the impact of correlated disorder.

Robotic pendant drop: containerless liquid for μs-resolved, AI-executable XPCS

The dynamics and structure of mixed phases in a complex fluid can significantly impact its material properties, such as viscoelasticity. Small-angle X-ray Photon Correlation Spectroscopy (SA-XPCS) can probe the spontaneous spatial fluctuations of the mixed phases under various in situ environments over wide spatiotemporal ranges (10-6-103 s /10-10-10-6 m). Tailored material design, however, requires searching through a massive number of sample compositions and experimental parameters, which is beyond the bandwidth of the current coherent X-ray beamline. Using 3.7-μs-resolved XPCS synchronized with the clock frequency at the Advanced Photon Source, we demonstrated the consistency between the Brownian dynamics of ~100 nm diameter colloidal silica nanoparticles measured from an enclosed pendant drop and a sealed capillary. The electronic pipette can also be mounted on a robotic arm to access different stock solutions and create complex fluids with highly-repeatable and precisely controlled composition profiles. This closed-loop, AI-executable protocol is applicable to light scattering techniques regardless of the light wavelength and optical coherence, and is a first step towards high-throughput, autonomous material discovery.

Polarization dependent light propagation in [Formula: see text] multilayer structure

[Formula: see text] is one of the exciting and outstanding semimetallic members of TMDCs, which has attracted immense attention for manipulating light propagation due to its inherent optical anisotropy and hyperbolic characteristic in the infrared frequency range. We investigate the dependence of the reflectance and transmittance of structures with a single and double [Formula: see text] thin film in terms of frequency and polarization angle of the incident wave. We find rich behaviors in the optical response of these structures due to their anisotropic permittivity tensors. Furthermore, we analyze the polarization state of transmitted and reflected waves through these structures. We demonstrate that these structures provide the ability to achieve desired polarization rotation for outgoing waves by tuning the frequency and polarization angle of the incident wave with respect to the principal axes of [Formula: see text] thin film. In particular, we elucidate the essential relevance of the optical response and polarization rotation of the double thin film structure to the in-plain twist angle of [Formula: see text] thin films. We explain that this structure permits comprehensive control of the polarization rotation of the outgoing waves by adjusting the twist angle of thin films. The proposed structure can be employed as an efficient light manipulator with the aim of application in communication, imaging, and information processing.

Time derivatives via interconnected waveguides

Electromagnetic wave-based analogue computing has become an interesting computing paradigm demonstrating the potential for high-throughput, low power, and parallel operations. In this work, we propose a technique for the calculation of derivatives of temporal signals by exploiting transmission line techniques. We consider multiple interconnected waveguides (with some of them being closed-ended stubs) forming junctions. The transmission coefficient of the proposed structure is then tailored by controlling the length and number of stubs at the junction, such that the differentiation operation is applied directly onto the envelope of an incident signal sinusoidally modulated in the time domain. The physics behind the proposed structure is explained in detail and a full theoretical description of this operation is presented, demonstrating how this technique can be used to calculate higher order or even fractional temporal derivatives. We envision that these results may enable the development of further time domain wave-based analogue processors by exploiting waveguide junctions, opening new opportunities for wave-based single operators and systems.

Micro mercury trapped ion clock prototypes with 10[Formula: see text] frequency stability in 1-liter packages

Modern communication and navigation systems are increasingly relying on atomic clocks. As timing precision requirements increase, demands for lower SWaP (size, weight, and power) clocks rise. However, it has been challenging to break through the general trade-off trend between the clock stability performance and SWaP. Here we demonstrate micro mercury trapped ion clock (M2TIC) prototypes integrated with novel micro-fabricated technologies to simultaneously achieve high performance and low SWaP. The M2TIC prototypes could reach the [Formula: see text]-stability level in 1 day with a SWaP of 1.1 L, 1.2 kg, and under 6 W of power. This stability level is comparable to the widely used rack-mount Microchip 5071A cesium frequency standard. These standalone prototypes survived regular commercial shipping across the North American continent to a government laboratory, where their performance was independently tested. The M2TIC sets a new reference point for SWaP and performance and opens opportunities for high-performance clocks in terrestrial and space applications.

Far-infrared transparent conductors

The long-standing challenge in designing far-infrared transparent conductors (FIRTC) is the combination of high plasma absorption edge (λ_p) and high conductivity (σ). These competing requirements are commonly met by tuning carrier concentration or/and effective carrier mass in a metal oxide/oxonate with low optical dielectric constant (ε_opt = 2-7). However, despite the high σ, the transparent band is limited to mid-infrared (λ_p < 5 μm). In this paper, we break the trade-off between high σ and λ_p by increasing the "so-called constant" ε_opt that has been neglected, and successfully develop the material family of FIRTC with ε_opt > 15 and λ_p > 15 μm. These FIRTC crystals are mainly octahedrally-coordinated heavy-metal chalcogenides and their solid solutions with shallow-level defects. Their high ε_opt relies on the formation of electron-deficiency multicenter bonds resulting in the great electron-polarization effect. The new FIRTC enables us to develop the first "continuous film" type far-infrared electromagnetic shielder that is unattainable using traditional materials. Therefore, this study may inaugurate a new era in far-infrared optoelectronics.

Deep-learning-based gas identification by time-variant illumination of a single micro-LED-embedded gas sensor

Electronic nose (e-nose) technology for selectively identifying a target gas through chemoresistive sensors has gained much attention for various applications, such as smart factory and personal health monitoring. To overcome the cross-reactivity problem of chemoresistive sensors to various gas species, herein, we propose a novel sensing strategy based on a single micro-LED (μLED)-embedded photoactivated (μLP) gas sensor, utilizing the time-variant illumination for identifying the species and concentrations of various target gases. A fast-changing pseudorandom voltage input is applied to the μLED to generate forced transient sensor responses. A deep neural network is employed to analyze the obtained complex transient signals for gas detection and concentration estimation. The proposed sensor system achieves high classification (~96.99%) and quantification (mean absolute percentage error ~ 31.99%) accuracies for various toxic gases (methanol, ethanol, acetone, and nitrogen dioxide) with a single gas sensor consuming 0.53 mW. The proposed method may significantly improve the efficiency of e-nose technology in terms of cost, space, and power consumption.

Perovskite photodetector-based single pixel color camera for artificial vision

Narrowband red, green, blue self-filtering perovskite photodetectors and a broadband white photodetector are incorporated into a single pixel imaging camera to mimic the long-, medium-, and short-wavelength cone cells and rod cells in human visual system, leading to the demonstration of high-resolution color images in diffuse mode.

Design and fabrication of a Wilkinson power divider with harmonic suppression for LTE and GSM applications

Conventional Wilkinson power dividers (WPDs) can provide acceptable performance close to the nominal center frequency. However, these WPDs can also exhibit poor out-of-band performance while requiring a large footprint. In order to improve on the current state of the art, a modified microstrip WPD is proposed that exhibits a substantially improved stopband and high isolation. A lowpass filter (LPF) structure is utilized in both branches of the power divider to provide harmonic suppression. According to the obtained results, the input return loss (|S₁₁|), output return loss (|S₂₂|), output insertion loss (|S₂₁|) and isolation (|S₃₂|) are better than 34.2 dB, 26.2 dB, 3.52 dB and 31.2 dB, respectively. The proposed modified WPD has a wide 20 dB stopband (from 2.54 GHz to 13.48 GHz) and filters the second to seventh harmonics with attenuation levels of greater than 20 dB. The proposed WPD has a small size of 33.8 mm × 27 mm (0.42 λg × 0.33 λg), where λg is the guided wavelength at the operating frequency of 1.8 GHz. The WPD has been fabricated and tested and shows good agreement between simulated and measured results and the proposed design has desirable characteristics for LTE and GSM applications.

Impinge Weyl advantages on light

Weyl semimetals are emerging topological materials with intriguing physical properties. Now this exotic matter may lead to novel photonic and optoelectronic applications.

Spectral sensitivity near exceptional points as a resource for hardware encryption

The spectral sensitivity near exceptional points (EPs) has been recently explored as an avenue for building sensors with enhanced sensitivity. However, to date, it is not clear whether this class of sensors does indeed outperform traditional sensors in terms of signal-to-noise ratio. In this work, we investigate the spectral sensitivity associated with EPs under a different lens and propose to utilize it as a resource for hardware security. In particular, we introduce a physically unclonable function (PUF) based on analogue electronic circuits that benefit from the drastic eigenvalues bifurcation near a divergent exceptional point to enhance the stochastic entropy caused by inherent parameter fluctuations in electronic components. This in turn results in a perfect entropy source for the generation of encryption keys encoded in analog electrical signals. This lightweight and robust analog-PUF structure may lead to a variety of unforeseen securities and anti-counterfeiting applications in radio-frequency fingerprinting and wireless communications.

Open-circuit and short-circuit loss management in wide-gap perovskite p-i-n solar cells

In this work, we couple theoretical and experimental approaches to understand and reduce the losses of wide bandgap Br-rich perovskite pin devices at open-circuit voltage (V_OC) and short-circuit current (J_SC) conditions. A mismatch between the internal quasi-Fermi level splitting (QFLS) and the external V_OC is detrimental for these devices. We demonstrate that modifying the perovskite top-surface with guanidinium-Br and imidazolium-Br forms a low-dimensional perovskite phase at the n-interface, suppressing the QFLS-V_OC mismatch, and boosting the V_OC. Concurrently, the use of an ionic interlayer or a self-assembled monolayer at the p-interface reduces the inferred field screening induced by mobile ions at J_SC, promoting charge extraction and raising the J_SC. The combination of the n- and p-type optimizations allows us to approach the thermodynamic potential of the perovskite absorber layer, resulting in 1 cm² devices with performance parameters of V_OCs up to 1.29 V, fill factors above 80% and J_SCs up to 17 mA/cm², in addition to a thermal stability T₈₀ lifetime of more than 3500 h at 85 °C.

Absolute dosimetry for FLASH proton pencil beam scanning radiotherapy

A paradigm shift is occurring in clinical oncology exploiting the recent discovery that short pulses of ultra-high dose rate (UHDR) radiation-FLASH radiotherapy-can significantly spare healthy tissues whilst still being at least as effective in curing cancer as radiotherapy at conventional dose rates. These properties promise reduced post-treatment complications, whilst improving patient access to proton beam radiotherapy and reducing costs. However, accurate dosimetry at UHDR is extremely complicated. This work presents measurements performed with a primary-standard proton calorimeter and derivation of the required correction factors needed to determine absolute dose for FLASH proton beam radiotherapy with an uncertainty of 0.9% (1[Formula: see text]), in line with that of conventional treatments. The establishment of a primary standard for FLASH proton radiotherapy improves accuracy and consistency of the dose delivered and is crucial for the safe implementation of clinical trials, and beyond, for this new treatment modality.

Pulse distortion caused by waveguide inhomogeneity in nonlinear optical wavelength converters

Low-noise integrated all-optical wavelength converters that can be operated in short pulse regime are essential tools to overcome contention resolution in a modern communication network, based on wavelength division multiplexing. Any imperfect functionality in such devices causes non-ideal optical power transfer to the converted data pulses. All imperfections during the preparation and operation of the wavelength converters can be addressed to the waveguide inhomogeneity which distorts data pulses to be converted. This paper reports different waveguide inhomogeneity effects on the pulse distortion while using periodically poled lithium niobate waveguide as wavelength converters. Three types of [Formula: see text]-based nonlinear optical processes, including second harmonic generation, difference frequency generation, and cascaded second harmonic generation/difference frequency generation are numerically studied to show that any constant, linear, and quadratic waveguide inhomogeneity causes short pulse (down to 1 ns) distortion in such wavelength converters. In addition, it is shown that the reconstruction of [Formula: see text]-shaped generated pulses is possible, when suitable upside-down quadratic variations of obtained inhomogeneity are deliberately induced in the waveguide. Notably, for pulsed second harmonic generation, the generated pulse can be compressed using an upside-down quadratic phase mismatch.

Research progress of large size SiC single crystal materials and devices

SiC semiconductor is the focus of recent international research. It is also an important raw material for China to achieve carbon emission peak and carbon neutrality. After nearly 20 years of research and development, we focus on the three types SiC crystals, n-type, p-type and semi-insulating, indicating the development of Shandong University for crystal growth. And defects control, electrical property, atomic polishing, and corresponding device authentication all obtain great progress. Total dislocation density of 6-inch n-type substrates decreases to 2307 cm^-2, where BPD (Basal Plane Dislocation) lowers to 333 cm^-2 and TSD (Threading Screw Dislocation) 19 cm^-2. The full width at half maximum (FWHM) (0004) rocking curves is only 14.4 arcsec. The resistivity reaches more than 1E + 12 Ω·cm for semi-insulating SiC and lower than 20 mΩ·cm for n-type SiC. The impurity concentrations in 6-inch high-purity semi-insulating (HPSI) SiC crystals reach extreme low levels. The devices made of various substrate materials have good performance.

Vertical organic electrochemical transistors for complementary circuits

Organic electrochemical transistors (OECTs) and OECT-based circuitry offer great potential in bioelectronics, wearable electronics and artificial neuromorphic electronics because of their exceptionally low driving voltages (<1 V), low power consumption (<1 µW), high transconductances (>10 mS) and biocompatibility^1-5. However, the successful realization of critical complementary logic OECTs is currently limited by temporal and/or operational instability, slow redox processes and/or switching, incompatibility with high-density monolithic integration and inferior n-type OECT performance^6-8. Here we demonstrate p- and n-type vertical OECTs with balanced and ultra-high performance by blending redox-active semiconducting polymers with a redox-inactive photocurable and/or photopatternable polymer to form an ion-permeable semiconducting channel, implemented in a simple, scalable vertical architecture that has a dense, impermeable top contact. Footprint current densities exceeding 1 kA cm^-2 at less than ±0.7 V, transconductances of 0.2-0.4 S, short transient times of less than 1 ms and ultra-stable switching (>50,000 cycles) are achieved in, to our knowledge, the first vertically stacked complementary vertical OECT logic circuits. This architecture opens many possibilities for fundamental studies of organic semiconductor redox chemistry and physics in nanoscopically confined spaces, without macroscopic electrolyte contact, as well as wearable and implantable device applications.