Electrical Modulation Research Articles

Electron tunneling through HgTe/CdTe quantum wells with all-electrical superlattice structures

We theoretical investigate the electron transport through HgTe/CdTe quantum wells (QWs) heterostructure interfaces with periodic electrical potential modulations in this work. We find Fabry–Pérot resonant tunneling with perfect transmission through a two dimensional topological insulator superlattice structure in HgTe/CdTe QWs, which is supposed to be experimentally observable. This unique feature indicates potential applications of Fabry–Pérot interferometers device. The transport properties of electrons tunneling through the superlattice structures can be adjusted by tuning the Fermi energy, electron incident angle, the electrical modulation numbers and modulation amplitude. We also find the enhanced Fabry–Pérot resonance tunneling due to the electric-induced Rashba spin–orbit interaction (RSOI). This all-electrical mechanism may pave a realistic way to control the electron transport in two dimension topological insulator from a device application perspective.

Gate-Modulated High-Response Field-Effect Transistor-Type Gas Sensor Based on the MoS2/Metal-Organic Framework Heterostructure.

The high surface-to-volume ratio and decent material properties of two-dimensional (2D) transition metal dichalcogenides (TMDs) make them advantageous as an active channel in field-effect transistor (FET)-type gas sensing devices. However, most existing TMD gas sensors are based on a two-terminal resistance-type structure and suffer from low responsivity and slow response, which has urged materials optimization as well as device engineering. Metal-organic frameworks (MOFs) have a large number of ordered binding sites in the pores that can specifically bind to gas molecules and can be decorated on TMD surfaces to enhance gas sensing capabilities. In this work, we successfully realize the FET-type gas sensor with MoS2-MOF as the channel. The fabricated gas sensor exhibits enhanced NH3 sensing performance (22.475 times higher in responsivity) as compared to the device with a bare MoS2 channel. In addition, the FET-type gas sensor geometry enables effective tuning of sensitivity through electrical gating based on the modulation over the channel carrier concentration. Furthermore, the dependence of responsivity on the MoS2 thickness is investigated as well to achieve an in-depth understanding of the electrical modulation mechanism of the MOF-decorated MoS2 gas sensors. The demonstrated results can pave an attractive pathway toward the realization of advanced high-response and tunable TMD-based gas sensing devices.

Electrical modulation of excitonic transition in monolayer tungsten disulfide on periodically poled ferroelectric substrates

Although the spectral investigation of monolayer two-dimensional transition metal dichalcogenide (1L-TMD) has been extensively performed for identifying modulation of excitonic transition, study of excitonic transition in ferroelectric/TMD hybrid structure is essential to understand and design high speed and low loss devices based on in-plane junctions. Here, we demonstrate electrical modulation of excitonic transition by transferring 1L-tungsten disulfide (WS2) onto a ferroelectric domain surface, a periodically poled lithium niobate (PPLN). We observe that exciton (A0) and trion (A−) emissions of 1L-WS2 are spatially modulated depending on the sign of the phase domain, such that A0 and A− emission is stronger at the positive (D+) and negative (D−) domain, respectively. In addition, different trends of excitonic transition of 1L-WS2 between D+ and D− domain are demonstrated by applying a back-gate bias voltage. The spatial modulation of electrical and optical characteristics of 1L-TMDs will help to design the homo- or hetero p-n junctions based on TMDs.

Novel low-cost high-speed optic–electric laser diode pigtail module packaging technology

• At present, the research and development of high-speed laser modules for communication are designed with ceramic components globally. • In module packaging without the ceramic part, the misalignment caused by the deformation results in coupling efficiency loss. • A new type of high-speed laser diode pigtail module is designed to change the structure of a laser module and remove ceramic and process parts. • A laser diode pigtail module package achieves the best coupling efficiency. A high-speed laser diode pigtail for wide-band fiber-optic communications is a key component in optical fiber user loop systems, optical fiber data communication systems, and cable television systems. With the advent of a new type of optic–electric high-speed laser, wide-band communication has emerged. These three systems constitute future mainstreams of optical fiber communications. However, high-speed laser diode pigtails used in module components and process assembly account for extremely high production costs. The proposed pigtail module eliminates ceramic parts and facilitates mass production of the components. An optic fiber (including a jacket) was placed into a ferrule sleeve. The optic fiber did not undergo laser damage, and its stability in the reliability test was ensured by the plastic jacket. The optic fiber terminal surfaces grind the 7° angle to enhance the surface quality of the connector, thereby avoiding reflection and incurring a power loss of 4%. Moreover, achieving alignment in a conventional laser module package without a ceramic part and fiber ferrule is a considerable challenge, and apparently, there are still some issues that need to be resolved. In conventional optical fiber module package, laser welding technique provides a superior joint strength. However, in module packaging without the ceramic part, the misalignment caused by the deformation results in coupling efficiency loss. Therefore, a novel design of laser diode pigtail module packaging is necessary. A transmitter optical subassembly device, receiver optical subassembly device, and transceiver pigtail module can be manufactured in a unified process package. By applying the low-cost packaging technique, the cost and fabrication time of the module packaging were reduced, and the fabrication yield was increased.

Experimental and theoretical insights into electronic properties of oxygen-doped MoTe2 field effect transistor

Modulating the electrical and photo-electrical properties is essential to enlighten the potential application in the case of field-effect transistors and other electronic devices. Molybdenum ditelluride (MoTe2), which has a limited energy gap and shows spin-orbit coupling, has piqued curiosity among two-dimensional (2D) transition metal dichalcogenides (TMDCs) and has appeared as a significant material with innovative electronic applications. In this work, we have reported the electrical modulation of multilayer MoTe2-FETs by gas doping under deep ultra-violet (DUV) light. After DUV treatment, the device characteristics were also investigated with oxygen doping. A shift in threshold voltage was observed from negative to positive back-gate voltage (Vbg), revealing a p-type doping effect. This doping effect is further confirmed through the Raman peaks, A1g and E12g were shifted towards higher wavenumbers. For pristine to 30-min doping intervals, the current ON/OFF ratio increased from 104 to 106 and the mobility of the device is enhanced from 22.36 cm2/V.s to 102.43 cm2/V.s. In addition, we used density functional theory (DFT) to investigate the impact of oxygen doping on the electrical and optical properties of MoTe2. The electronic bandgap was determined to be 0.8 eV, which can be a promising material for lower energy devices. The oxygen-doped MoTe2-based field-effect transistors are predicted to be a promising contender for low and high-temperature applications based on the highly intense peak of absorption spectra in the ultra-violet and visible regions of electromagnetic spectra.

Applicability of an electrical resistance modulator device in the rehabilitation of a person with spinal cord injury

INTRODUCTION: Technology is in rapid and continuous evolution. The recovery of functions, motor, and cognitive activities benefits from it to define new outcome measures and new rehabilitation processes. This study evaluates the applicability of an electrical resistance modulator device for rehabilitation purposes for a person with spinal cord injury. MATERIALS AND METHODS: The study sample consisted of 10 healthy, able-bodied subjects assessed in a light wheelchair. A resistance training mode is compared using the electrical resistance modulator device and a standard strength training protocol with the aid of two weights, through an electromyographic and a kinematic evaluation with a triaxial accelerometer. The movements investigated consist of arm abduction-adduction, arm elevation-extension and elbow flexion-extension. RESULTS AND DISCUSSION: In the flexion-extension gesture of the arm, there is a greater symmetry of muscle activation and less activation of the muscles not directly involved in the movement during the use of the electrical resistance modulator device. In the flexion-extension of the elbow and flexion-extension of the shoulder, the muscle power expressed through the electrical device is greater, while in the abduction-adduction of the shoulder, it is more significant with weights. For the joint Range of Motion, the duration of the motion cycles and their symmetry, there are no significant differences between the two experimental conditions. CONCLUSIONS: The study results confirm that training for increasing muscle strength in a person with spinal cord injury can be performed using the electrical resistance modulator device. There are no contraindications to its use nor greater risks for the subject’s health. Further studies are needed to investigate the benefits of using the electrical device in the early stages of rehabilitation of a person with spinal cord injury.

Electrically switchable capabilities of conductive polymers-based plasmonic nanodisk arrays.

The electrically dynamic regulation of plasmonic nanostructures provides a promising technology for integrated and miniaturized electro-optical devices. In this work, we systematically investigate the electrical regulation of optical properties of plasmonic Au nanodisk (AuND) arrays integrated with different conductive polymers, polypyrrole (PPy), polyaniline (PANI), and poly(3,4-ethylenedioxythiophene) (PEDOT), which show their respective superiority of electrical modulation by applying the appropriate low voltages. For the hybrid structure of polymer-coated AuND arrays, its reflection spectrum and corresponding structural color are dynamically modulated by altering the complex dielectric function of the covering nanometer-thick conductive polymers based on the electrically controlled redox reaction. Due to the distinct refractive index responses of different polymers on the external voltage, polymer-coated AuND arrays exhibit different spectral variations, response time, and cycle stability. As a result, the reflection intensity of PPy-coated AuND arrays is mainly tailored by increasing optical absorption of the PPy polymer over a broad spectral range, which is distinguished from the wavelength shift of the resonance modes of AuND arrays induced by the other two polymers. Additionally, AuND arrays integrated with both PANI and PEDOT polymers exhibit a rapid switching time of less than 50 ms, which is 5 times smaller than the case of the PPy polymer. Most importantly, PPy-coated AuND arrays exhibit excellent cycle stability over 50 cycles compared to the other two polymers integrated devices. This work demonstrates a valuable technique strategy to realize high-performance polymer-coated dynamically tunable nanoscale electro-optical devices, which has especially significance for smart windows or dynamic display applications.

Over 10 kA/cm2 inductive current sustaining capability demonstrated in GaN-on-GaN pn junction with high ruggedness

This work presents specific investigation on the simultaneous demonstration of superior forward-current-sustaining and avalanche-breakdown-dissipating capability in GaN pn junction, which is critical for the ruggedness of future high-power-figure-of-merit vertical GaN MOSFET in tolerating inductive current strikes. Based on the doping profile design and edge electric field modulation in the pn junction, over 10 kA/cm2 current handling capability in both forward and reverse direction has been achieved. Meanwhile, no degradation in the device performance has been observed under continuous forward current stress tests and consecutively repetitive unclamped inductive switching tests, revealing the excellent ruggedness of state-of-art GaN-on-GaN pn junction against the inductive energy transients, thus promising reliable operation in the vertical power device applications.

Gd/Mn Co-Doped CaBi4Ti4O15 Aurivillius-Phase Ceramics: Structures, Electrical Conduction and Dielectric Relaxation Behaviors.

In this work, Gd/Mn co-doped CaBi4Ti4O15 Aurivillius-type ceramics with the formula of Ca1-xGdxBi4Ti4O15 + xGd/0.2wt%MnCO3 (abbreviated as CBT-xGd/0.2Mn) were prepared by the conventional solid-state reaction route. Firstly, the prepared ceramics were identified as the single CaBi4Ti4O15 phase with orthorhombic symmetry and the change in lattice parameters detected from the Rietveld XRD refinement demonstrated that Gd3+ was successfully substituted for Ca2+ at the A-site. SEM observations further revealed that all samples were composed of the randomly orientated plate-like grains, and the corresponding average grain size gradually decreased with Gd content (x) increasing. For all compositions studied, the frequency independence of conductivity observed above 400 °C showed a nature of ionic conduction behavior, which was predominated by the long-range migration of oxygen vacancies. Based on the correlated barrier hopping (CBH) model, the maximum barrier height WM, the dc conduction activation energy Edc, as well as the hopping conduction activation energy Ep were calculated for the CBT-xGd/0.2Mn ceramics. The composition with x = 0.06 was found to have the highest Edc value of 1.87 eV, as well as the lowest conductivity (1.8 × 10−5 S/m at 600 °C) among these compositions. The electrical modules analysis for this composition further illustrated the degree of interaction between charge carrier β increases, with an increase in temperature from 500 °C to 600 °C, and then a turn to decrease when the temperature exceeded 600 °C. The value of β reached a maximum of 0.967 at 600 °C, indicating that the dielectric relaxation behavior at this temperature was closer to the ideal Debye type.

Boolean logic gates implemented by a single photonic neuron based on a semiconductor Fano laser

We propose and numerically demonstrate a high-speed photonic neuron model using a single semiconductor Fano laser (FL) under electrical modulation that can mimic the Class 1 and Class 3 neuronal dynamics. In this model, the unwanted relaxation oscillation found in the spiking dynamics of conventional semiconductor lasers can be suppressed by the formation of a Fano mirror. The Boolean logic operations are tested based on the dynamics of the photonic neuron combined with the all-or-none law and time encoding method, which are the key properties of biological neurons. The results show that the Boolean logic gates can be successfully implemented in the proposed photonic neuron. Importantly, as a unique type of microscopic laser, the FL has the potential to develop integrated neuromorphic photonic computing systems.

Thermal properties and application of a novel CaCl2·6H2O/expanded graphite shape-stabilized composite phase change material for electric radiant heating

In recent years, electric heating has been popularized and applied as a heating form of clean energy. In order to realize the peak shifting and valley filling of heating electricity to reduce heating cost and improve energy efficiency, phase-change heat storage electric heating system has become a hot topic of research and application. In this paper, using CaCl2·6H2O as phase change material (PCM), SrCl2·6H2O as nucleating agent and expanded graphite (EG) as porous supporting carrier, a novel shape-stabilized composite PCM was prepared by melt blending method. The thermal physical properties of shape-stabilized composite PCM with different prepared proportions were studied through experiments. The experimental results showed that 88%CaCl2·6H2O + 2%SrCl2·6H2O + 10%EG (50 mesh to 100 mesh) is the optimal prepared proportion of the shape-stabilized composite PCM. The composite PCM with a latent heat of 172.92 kJ/kg, a thermal conductivity of 3.85 W/m·K and a super-cooling degree less than 2 °C, has good shape stability and thermal reliability. A kind of novel electric heating module was fabricated with prepared composite PCM and carbon fiber heating wire. The heat storage and release characteristics of the module were studied through experiments, and the effects of different electric heating power, EG particle size and module size on its thermal performance were also studied. The experimental results showed that the internal temperature of the module was uniform and the module can maintain stable heat dissipation for a long time. The temperature fluctuation of the module surface is relatively small. In summary, the module can meet the heating requirements of buildings when applied to electric radiant heating in the building, and the CaCl2·6H2O/EG shape-stabilized composite PCM shows great promise in building energy saving.

Electrical tunable topological valley photonic crystals for on-chip optical communications in the telecom band

Abstract On-chip optical communications are in increasingly demand for low-loss, small-footprint and power-efficient waveguiding solutions in the telecom band. However, most integrated optical circuits suffer from high propagation loss and low integration degree. Through manipulating the valley-dependent topological phase of light, we have experimentally demonstrated both robust optical transport and electrical modulation of lightwaves at telecom wavelengths in the valley photonic crystals. With the adoption of valley kink states, the 25 Gbit/s optical signal at 1550 nm is successfully transmitted through a highly twisted interface. Furthermore, an extreme high data rate of 100 Gbit/s is demonstrated with such topological waveguide by wavelength division multiplexing. The electrical tunability of the topological modulators based on thermo-optic effect is also verified, opening a novel route towards active valley kink photonic devices. Our study shows a great possibility of making use of the topological protection in building up high-speed datalinks on a chip.

Numerical investigation on thermal performance of battery module with LCP‐AFC cooling system applied in electric vehicle

AbstractTo improve the thermal performance of electric vehicle batteries, a novel cooling system of liquid cold plates coupled with air flow channels (LCP‐AFC) for battery thermal management was proposed. Three‐dimensional models were established for simulation. The effects of five factors on the heat dissipation of the electric vehicle battery module were studied, which included the battery discharge rate, inlet temperature of cooling liquid, nanofluids, airflow velocity, liquid, and air flow directions. The results showed that the maximum temperature Tmax and temperature difference ΔT of the battery module under 1 C discharge rate could be reduced by 1.1°C and 0.92°C compared to the single liquid cooling. Comparing the LCP‐AFC with single air cooling, the Tmax and ΔT of the battery module under 4 C discharge rate could be reduced by 18.74°C and 2.71°C. The temperature uniformity of the battery module was not satisfied with the inlet temperature of the cooling liquid, which was lower than 15°C. The heat transfer performance was improved by adding Al, Cu, or Ag nanoparticles into the deionized water. Among them, Ag–water nanofluid had the most significant cooling effect. Parallel flow indicated better thermal performance than cross flow and counter flow. The developed cooling system of LCP‐AFC offers a new method to design lithium‐ion battery thermal management system for controlling temperature distribution of a battery module.

Electrical based cancer therapy for solid tumours - Theranostics approach

According to the Centers for Disease Control and Prevention (CDC), more than 700,000 women have been diagnosed with cancer in the last five years. Cancers of the breast, cervical, ovarian, lung, uterine, and thyroid are among the most prevalent cancers in women. For over a century, surgery, radiation, and pharmaceutical treatment have been the cornerstones of cancer treatment. When used alone or in combination, these medicines have improved therapeutic outcomes for patients with a variety of solid and diffuse malignancies, but there is still a significant unmet demand for improved survival and quality of life. As seen by the advancement from first laboratory observations to the completion of multiple clinical trials, electrical-based cancer therapies have made remarkable progress as a potential therapeutic agent for the treatment of many solid tumours. Electric field lines have the opportunity to utilize force on charged molecules, which distinguishes them. By interacting with polar molecules like tubulin and disrupting the mitotic spindle, electric fields can potentially have an antimitotic effect on cells, reducing or stopping cell proliferation. In a range of tumour types, Tumor Treating Fields (TTFields) have been found to have anti-mitotic effects. The combined effect of TTFields and paclitaxel increased apoptosis-mediated anti-mitotic tumour progression inhibition. In conclusion, this study provides an overview of the most common female cancers as well as an up-to-date assessment of the therapy options for these diseases. It also covers the use of electric module therapy for certain tumours, its putative mechanisms, and a synthesis of its benefits and drawbacks during cancer treatment.

Electrical conductivity and relaxation phenomena in Li2O·B2O3 based glass and glass-ceramic: A comprehensive and comparative analysis

This work reports a detailed investigation on the electrical conductivity and dielectric relaxation phenomena in Li2O·B2O3 based glass and glass-ceramic materials. Measurements reveal that the electrical conductivity of glass-ceramic is lower than glass. This owes to occurrence of grain boundaries which impede the mobility of charge carriers in glass-ceramic as confirmed by FESEM micrographs. The frequency-dependent behavior of electrical conductivity, within the measured temperature range, is analysed using Jonscher's power law. It is found that the conductivity rises with an increase in temperature and the range of conductivity reveals the semiconducting behavior of the material. The ac conductivity mechanism of system is observed to follow the overlapping large polaron tunneling model. The conduction and relaxation mechanism studies are performed using electric modulus and impedance spectroscopy within the frequency and temperature ranges varied from 103 Hz to 107 Hz and 593 K–773 K, respectively. Analysis of the relaxation mechanism in both samples is performed employing Kohlrausch-William-Watts (KWW) model, which reveals that the charge carriers are following non-Debye type relaxation. To distinguish between the contribution of grain boundaries and grains in the relaxation mechanism, a combined analysis of complex electric module and impedance spectroscopy has been discussed.

Strain and external electric field modulation of the electronic and optical properties of GaN/WSe2 vdWHs

Recently, the GaN/WSe2 van der Waals heterostructures (vdWHs) were successfully synthesized in experiments, providing a pathway for designing the nitride semiconductor materials with transition metal dichalcogenides (TMDs) heterostructures. To insight into the physical mechanism of the GaN/WSe2 vdWHs, the geometrical, electronic and optical properties of the systems are examined based on the first-principles calculations. Our results indicate that the GaN/WSe2 heterostructures exhibit typical type-I band alignment with the bandgap values around 2.20 eV at HSE06 level. Biaxial and external electric field not only can cause the evolution of the band alignment to transfer from type-I to type-II, but also can realize semiconductor-metal transition. In addition, compressive strain enhances the light absorption intensity in the ultraviolet region and tensile strain enables the GaN/WSe2 vdWHs to appear a distinct peak in infrared (IR) region. These flexible and tunable characteristics of type-I GaN/WSe2 vdWHs are more convenient for the design of IR detectors, photovoltaic and light emission devices.

Detection of DNA Hybridization Beyond the Debye Screening Length by CMOS Capacitive Sensors

Capacitive sensors are very promising to provide label-free and real-time biological detection for point-of-care diagnostic applications. However, the Debye charge screening effect severely hinders the detection under high ionic strength condition, such as in human serum. Therefore, most measurements are made indirectly in diluted solutions. To solve this problem, electric field modulation between the interdigitated sensing electrodes is applied in this study to increase the Debye length. For DNA (deoxyribonucleic acid) measurements, the two designs operating around 90 and 40 MHz exhibited sensitivities of 2.6 fF/log[DNA] and 10.8 fF/log[DNA] up to 100 fM and a response time of 12 minutes.

Experimental Demonstration of Constant-Envelope OFDM to Reduce Intermodulation Impairments and Increase Robustness Against Fiber Nonlinearities

Direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) systems have been proposed as a well-suited solution for cost-sensitive applications, but also for metro/regional optical links. In this article, we experimentally demonstrate tolerance enhancements of constant-envelope OFDM (CE-OFDM) signals towards Mach–Zehnder modulator (MZM) intermodulation impairments and fiber nonlinear Kerr effects. The additional tolerance is achieved by the reduced peak-to-average power ratio (PAPR) of CE-OFDM signals, unlike conventional OFDM signals that inherently possess high PAPR values and therefore, are prone to distortions induced by the above-mentioned impairments. The experiments show that the transmission of CE-OFDM signals with PAPR <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$=3$</tex-math></inline-formula> dB over 1000 km of dispersion-uncompensated standard single-mode fiber (SSMF) is successfully accomplished. The proper choice of the MZM bias point, as well as the electrical phase modulation index, provides link length enlargements at the same bit error rate. An enlargement around 320 km of SSMF was achieved with an optical launch power of 10 dBm and with a guard-band of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx 16\%$</tex-math></inline-formula> of the signal bandwidth when compared to conventional DDO-OFDM systems.

Flow control characteristics of the digital and mechanical redundancy control electric modulation valve

Flow control characteristics of the digital and mechanical redundancy control electric modulation valve

Electric Field Modulation of 2D Perovskite Excitonics

Multiquantum-well (MQW) perovskite is one of the forerunners in high-efficiency perovskite LED (PeLEDs) research. Despite the rapid inroads, PeLEDs suffer from the pertinent issue of efficiency decrease with increasing brightness, commonly known as "efficiency roll-off". The underlying mechanisms are presently an open question. Herein, we explicate the E-field effects on the exciton states in the archetypal MQW perovskite (C6H5C2H4NH3)2PbI4, or PEPI, in a device-like architecture using field-assisted transient spectroscopy and theoretical modeling. The applied E-field results in a complex interplay of spectral blueshifts and enhancement/quenching of the different exciton modes. The former originates from the DC Stark shift, while the latter is attributed to the E-field modulation of the transfer rates between bright/dark exciton modes. Importantly, our findings uncover crucial insights into the photophysical processes under E-field modulation contributing to efficiency roll-off in MQW PeLEDs. Electrical modulation of exciton properties presents exciting possibilities for signal processing devices.