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Resistive switching (RS) has been studied for several applications such as information storage and bio-inspired computing, although reliability issues still prevent their massive use. In this work, we present a novel observation of trapping activity that imposes giant random conductance fluctuations, up to 3 orders of magnitude, resembling RTN in RS devices based on TiO2, HfO2 and hexagonal boron nitride (h-BN) under reading voltages (~ 0.1 V). These events appeared reproducible for all the aforementioned RS device types in sequential measurements and under different bias. This behavior is very beneficial to ensure recognition of the device’s two-state in applications such as stochastic computing integrated circuits (ICs).

In this work, a large-area MoS2/graphene barristor device, with an electrically tunable Schottky barrier height, has been studied for detection of various gaseous analytes. The Schottky barrier height could be modulated by over 0.65 eV, allowing the drain current to be tuned by many orders of magnitude. Using diluted NO2 and NH3 gases as analytes, the performance of the barristor device was compared with individual MoS2 and graphene based planar FETs, where the barristor device outperformed its counterparts in terms of response magnitude and limit of detection. Due to the atomically thin nature of MoS2 and graphene, electric field applied to one material could not be fully screened from the other one, which allowed both materials to act as a composite structure when analyte molecules interacted with the barristor device. This apparently reversed the dopant behavior of NO2 and NH3, while increasing the device sensitivity through subthreshold operation. Both conductance and capacitance based measurements are presented to highlight the charge transfer and barrier height modulation, to support the unique sensing mechanism observed in the 2D barristor device. A lower limit of detection in low ppb is established for NO2 and low ppm for NH3, which could be further tuned by altering gate-drain bias conditions.

The scalable synthesis and transfer of large-area graphene underpins the development of nanoscale photonic devices ideal for new applications in a variety of fields, ranging from biotechnology, to wearable sensors for healthcare and motion detection, to quantum transport, communications, and metrology. We report room-temperature zero-bias thermoelectric photodetectors, based on single- and polycrystal graphene grown by chemical vapor deposition (CVD), tunable over the whole terahertz range (0.1-10 THz) by selecting the resonance of an on-chip patterned nanoantenna. Efficient light detection with noise equivalent powers

As an emerging member of the colloidal semiconductor quantum dot materials family, intraband quantum dots are being extensively studied for thermal infrared sensing applications. High-performance detectors can be realized using a traditional p-n junction device design; however, the heavily doped nature of intraband quantum dots presents a new challenge in realizing diode devices. In this work, we utilize a trait uniquely available in a colloidal quantum dot material system to overcome this challenge: the ability to blend two different types of quantum dots to control the electrical property of the resulting film. We report on the preparation of binary mixture films containing midwavelength infrared Ag2Se intraband quantum dots and the fabrication of p-n heterojunction diodes with strong rectifying characteristics. The peak specific detectivity at 4.5 μm was measured to be 107 Jones at room temperature, which is an orders of magnitude improvement compared to the previous generation of intraband quantum dot detectors.

Electronic microdevices of self-bending coronene crystals are developed to reveal an unexplored link between mechanical deformation and crystal function. First, a facile approach towards length/width/curvature-controllable micro-crystals through bottom-up solution crystallization was proposed for high processability and stability. The bending crystal devices show a significant increase beyond seven orders of magnitude in conductivity than the straight ones, providing the first example of deformation-induced function enhancement in crystal materials. Besides, double effects caused by bending, including the change of π electron level as well as the enhancement of carrier mobility, were determined, respectively by the X-ray photoelectric spectroscopy and X-ray crystallography to coexist, contributing to the conductivity improvement. Our findings will promote future creation of flexible organic crystal systems with deformation-enhanced functional features towards customized smart devices.

This paper proposes a new structure named a Side Contact lateral Doping Field Effect Diode (SLFED) to overcome the short channel effects of a regular field effect diode (FED). The fabrication of this new structure is simple that can be fabricated by the standard CMOS process technology, and it offers good electrical characteristics. Furthermore, a comprehensive analysis of FEDs has presented. Our results show that the calculated Ion/Ioff ratio is several orders of magnitude larger than of the regular FED. For simulating the structures, we have applied semiconductor device simulation tools.

The EMDrive is a proposed propellantless propulsion concept claiming to be many orders of magnitude more efficient than classical radiation pressure forces. It is based on microwaves, which are injected into a closed tapered cavity, producing a unidirectional thrust with values of at least 1 mN/kW. This was met with high scepticism going against basic conservation laws and classical mechanics. However, several tests and theories appeared in the literature supporting this concept. Measuring a thruster with a significant thermal and mechanical load as well as high electric currents, such as those required to operate a microwave amplifier, can create numerous artefacts that produce false-positive thrust values. After many iterations, we developed an inverted counterbalanced double pendulum thrust balance, where the thruster can be mounted on a bearing below its suspension point to eliminate most thermal drift effects. In addition, the EMDrive was self-powered by a battery-pack to remove undesired interactions due to feedthroughs. We found no thrust values within a wide frequency band including several resonance frequencies and different modes. Our data limit any anomalous thrust to below the force equivalent from classical radiation for a given amount of power. This provides strong limits to all proposed theories and rules out previous test results by at least two orders of magnitude.

Practical application of surface-enhanced Raman spectroscopy (SERS) is greatly limited by the inaccurate quantitative analyses due to the measuring parameter's fluctuations induced by different operators, different Raman spectrometers, and different test sites and moments, especially during the field tests. Herein, we develop a strategy of quantitative SERS for field detection via designing structurally homogeneous and ordered Ag-coated Si nanocone arrays. Such an array is fabricated as SERS chips by depositing Ag on the template etching-induced Si nanocone array. Taking 4-aminothiophenol as the typical analyte, the influences of fluctuations in measuring parameters (such as defocusing depth and laser powers) on Raman signals are systematically studied, which significantly change SERS measurements. It has been shown that the silicon underneath the Ag coating in the chip can respond to the measuring parameters' fluctuations synchronously with and similar to the analyte adsorbed on the chip surface, and the normalization with Si Raman signals can well eliminate the big fluctuations (up to 1 or 2 orders of magnitude) in measurements, achieving highly reproducible measurements (mostly

Achieving high spinning speed is critical to the production efficiency and viable application of fiber species. Graphene fiber (GF) has recently emerged as a carbonaceous fiber with excellent functionality. However, the extremely low wet spinning speed of GF has limited its applications. We realized high-speed blow spinning of neat GF and fabric by modulating the rheological properties of the graphene oxide (GO) dispersion. We achieved a speed of 556 m min-1, 2 orders of magnitude faster than that for wet spinning. We chose ultrahigh molecular weight polymers as transient additives to circumvent the intrinsic barrier effect of GO and achieve high spinning dope stretchability at low polymer percentages-down to 25 wt %. Minimizing the polymer additive content ensures the high electrical/thermal conductivity of the blow-spun fiber and fabric. This work provides insight into the unique flow properties of 2D sheets and will promote the efficient production of graphene-based fibrous materials.

Optical tweezers enable the manipulation of micro- and nanodielectric particles through entrapment using a tightly focused laser. Generally, optical trapping of submicron size particles requires high-intensity light in the order of MW/cm2. Here, we demonstrate a technique of stable optical trapping of submicron polymeric beads on nanostructured titanium surfaces (black-Ti) without the use of lasers. Fluorescent polystyrene beads with a diameter d = 20-500 nm were successfully trapped on black-Ti by low-intensity focused illumination of incoherent light at λ = 370 m from a Hg lamp. Light intensity was 5.5 W/cm2, corresponding to a reduced light intensity of 6 orders of magnitude. Upon switching off illumination, trapped particles were released from the illuminated area, indicating that trapping was optically driven and reversible. Such trapping behavior was not observed on nonstructured Ti surfaces or on nanostructured silicon surfaces. Thus, the Ti nanostructures were demonstrated to play a key role.

Acoustic handling of nanoparticles in resonating acoustofluidic devices is often impeded by the presence of acoustic streaming. For micrometer-sized acoustic chambers, this acoustic streaming is typically driven from the fluid-solid interface by viscous shear-stresses generated by the acoustic actuation. AC electroosmosis is another boundary-driven streaming phenomena routinely used in microfluidic devices for handling of particle suspensions in electrolytes. Here, we study how streaming can be suppressed by combining ultrasound acoustics and AC electroosmosis. Based on a theoretical analysis of the electrokinetic problem, we are able to compute numerically a form of the electrical potential at the fluid-solid interface, which is suitable for suppressing a typical acoustic streaming pattern associated with a standing acoustic half-wave. In the linear regime, we even derive an analytical expression for the electroosmotic slip velocity at the fluid-solid interface, and use this as a guiding principle for developing models in the experimentally more relevant nonlinear regime that occurs at elevated driving voltages. We present simulation results for an acoustofluidic device, showing how implementing a suitable AC electroosmosis results in a suppression of the resulting streaming in the bulk of the device by two orders of magnitude., Comment: 12 pages, 8 pdf figures, compiled using JASAnew.cls

Graphene-based structures have found widespread applications in the fabrication of superior composite materials, conductors, and sensors owing to their excellent properties. Molecular dynamics (MD) simulation is often used to gain an in-depth understanding of the mechanical behaviors of those structures. However, MD simulation of mesoscale graphene structures faces great challenges due to its limited model size or high computation cost. In this work, we proposed a multilayer coarse-grained (CG) MD model which coarsens graphene layers in both planar and thickness directions. We systematically investigated the effect of coarse-graining on simulation accuracy in the CG-MD model. The optimal coarse-graining parameters for simulating the mechanical behaviors of graphene in tension, shearing, adhesion, bending, and self-folding were obtained. Our optimal CG-MD model enabled the simulation of relatively large-scale graphene structure with 1 ∼ 2 orders of magnitude increase in length and 3 ∼ 4 orders of magnitude reduction in computational time compared with the all-atom (AA) model, offering a valuable tool for designing and exploring graphene-based novel materials.

Here, a novel Au Wedge-enhanced Raman spectroscopy (WERS) substrate is proposed. The electric field enhancement factor and the effective mode field radius with varying geometry parameters are investigated. The proper excitation wavelength 633 nm is obtained. The practical application of WERS substrate is discussed. The Au WERS not only can provide a continuous extremely highly localized electric field as surface-enhanced Raman scattering (SERS) hotspots, but also can offer 10 orders of magnitude of SERS enhancement factor. The corresponding results reveal that WERS substrate will be widely applied in optics, biology, chemistry and other fields.

Electro-optic modulation based on a graphene nanoelectromechanical system (NEMS) with superlubricity is proposed and systematically theoretical investigated. We demonstrate that the superlubricity greatly improve the performance of photoelectric modulators based on graphene NEMS due to its extremely low coefficient of friction. The modulation voltage of graphene NEMS electro-optic modulation with superlubricity can be reduced to 200 mV, which is 1–3 orders of magnitude larger lower than that of the traditional electro-optical modulator, giving rise to a dramatic reduction of the power consumption of the modulator by approximately 3 orders of magnitude. The modulation response speed can reach nanoseconds, which is 4 orders of magnitude higher than the speed of traditional mechanical electro-optic modulation. At the same time, this modulator has a very wide modulation wavelength range and is not sensitive to the angle of incident light. Two-dimensional material devices, incorporated with mechanical modulation and superlubricity, will have important applications in optoelectronics and optical communication.

While ionic flow over graphenic structures creates electromotive potential, there is a need to understand the local carrier density induced in graphene without any electrode-induced Fermi-level pinning. Here, we show the electrolyte-flow induced localized doping in graphene via inspecting its Raman phononic energy. Graphene's Fermi energy level has a logarithmic dependence to the flow velocity over 2 orders of magnitude of velocity (∼100 μm s-1 to 10 mm s-1). A theoretical model of the electric double layer (EDL) during ionic transport is used to correlate the Fermi level of graphene with the flow rate and the electronic structure (HOMO-LUMO levels) of the ionic species. This correlation can allow us to use graphene as a reliable, non-invasive, optical flow-sensor, where the flow rates can be measured at high spatial resolution for several lab-on-a-chip applications.

The review contains information on the properties of phase-change materials (PCM) and the possibilities of their use as the basis of thermal energy storage. Special attention is given to PCMs with a phase transition temperature ranging between 20 and 80°C since such materials can be effectively used to reduce temperature variations in residential and industrial rooms. Thus, the application of PCMs in the construction industry enables one to considerably reduce the power consumption and reduce the environmental impact of industrial facilities. Thermophysical characteristics of the main types of PCMs are presented. The heat balance for a room with walls made of PCM-added materials is estimated. The predictions demonstrate that such structures can stabilize the temperature in practical applications as a result of usage of such materials. The potential of wide application of PCMs as a basis for thermal energy storage is limited due to very low conductivity (less than 1 W/(m K)) specific for these materials. Hence, the option of increasing the material conductivity by adding some carbon nanotubes whose thermal conductivity is four to five orders of magnitude greater than that of the base material is examined. The numerical predictions of the heat-conduction enhancement in a PCM doped with carbon nanotubes and the preliminary experiments indicate that a PCM with approximately 20% carbon nanotubes can enhance the material heat conductivity by two to four times.

The present work describes the preparation and the investigation of the room temperature electrical and optical properties of a series of liquid nanocomposites (lnC) prepared with different concentrations of multiwalled carbon nanotubes (MWCNT) in a variety of liquid matrices: glycerin, Vaseline, glucose, propylene glycol and silicone oil (SIO). Special attention is deserved to the SIO matrix, owing to its convenient electrical properties for our purposes. We verified that a small percent fraction of MWCNT dispersed along the SIO matrix is capable of improving the electrical conductivity of the matrix by orders of magnitude, indicating that the MWCNT strongly participates in the electrical conduction mechanism. Also, the application of an external electric field to this lnC resulted in large changes in the optical transmittance, that were interpreted as a consequence of the fieldinduced MWCNT alignment into the liquid matrix. The characteristics of such a new category of nanocomposite in the liquid state suggest further studies.

Present GaN technology consists primarily of heteroepitaxial, lateral high electron mobility transistors; however, high-power devices would be much more efficiently manufactured with a vertical geometry due to better blocking voltage scaling. This technology has yet to be realized due to the inconsistency of GaN wafer properties. These inconsistencies can be detected with several long-range, non-destructive techniques including Raman spectroscopy, optical profilometry, and photoluminescence mapping. In particular, Raman spectroscopy is an effective tool for determining the carrier concentration of GaN substrates and whether the wafers are uniform or inhomogeneous. In this work, vertical p-i-n GaN diodes are fabricated using both uniform and inhomogeneous wafers determined by using the A1 Raman peak position to monitor carrier concentration. The inhomogeneous samples have regular patterns of varying conductivity as a result of electron-donating defects brought about by changes in crystal stress. By avoiding these defects, we have found that diode performance improves by increasing the +/− 10 V rectification ratio by up to a factor of 5X and reducing the 200 V reverse bias leakage current by several orders of magnitude. Using the higher quality substrates with uniform electron carrier concentrations can improve the rectification ratio by another order of magnitude.

Dual-color photodetection can increase detection accuracy due to the specific information from different wavelengths. Traditional dual-color detectors are based on double optical modules or photovoltage devices, which suffer from huge system weight or low gain. In this Letter, a novel dual-color photodetector with Ge/Graphene/CdS sandwich profile is proposed. While visible and infrared light is mainly absorbed by the CdS and Ge layers, respectively, photoelectrical signals from two wavelengths both conducted by graphene are extracted on time-sequence with different sampling frequencies. Based on a tailored interface process and epitaxy InGaAs instead of bulk Ge layer, the difference in response speed more than 3 orders of magnitude (76 kHz/14 Hz) was realized. Due to the photogating effect, the high gain was obtained for both wavelengths, and a photoresponse enhancement originated from the overlapping of local photogating field is observed. The device provided a new solution for high-gain and CMOS-compatible dual-color photodetection.

The anisotropic magnetoresistance film is an important core material for developing the magnetic sensors. Here, Ta(5)/MgO(3)/NiFe(10)/MgO(3)/Ta(3) multilayers (in nanometer) were prepared by magnetron sputtering and further applied to construct a sensor element by combining with the Wheatstone bridge. The 1/f noise of the sensor element was greatly reduced by three orders of magnitude after annealing at 400 °C for 7200 s, which was mainly due to the significant microstructural changes during the annealing. However, when the sensor element was applied to detect the magnetic signal of a magnetic code disk with 512 N–S magnetic poles, the output voltage signal of the sensor displayed a large fluctuation of ± 0.05 V. In order to reduce the voltage fluctuation, a magnetic sensor chip by using a parallelly arranged multi-path Wheatstone bridges and auto-gain compensation structure was designed, and magnetic sensor elements and the high-performance computing drive module were prepared. The output voltage fluctuation of the magnetic sensor was reduced by about 90% and approached to ± 0.005 V. These findings provide an important basis for the practical application of NiFe-based magnetic sensing film materials.

Optofluidic biolasers have emerged as promising tools for biomedical analysis due to their strong light-matter interactions and miniaturized size. Recent developments in optofluidic lasers have opened a new Frontier in monitoring biological processes. However, most biolasers require precise recording of the lasing spectrum at the single cavity level, which limits its application in high-throughput applications. Herein, a microdroplet laser array encapsulated with living Escherichia coli was printed on highly reflective mirrors, where laser emission images were employed to reflect the dynamic changes in living organisms. The concept of image-based lasing analysis was proposed by quantifying the integrated pixel intensity of the lasing image from whispering-gallery modes. Finally, dynamic interactions between E. coli and antibiotic drugs were compared under fluorescence and laser emission images. The amplification that occurred during laser generation enabled the quantification of tiny biological changes in the gain medium. Laser imaging presented a significant increase in integrated pixel intensity by 2 orders of magnitude. Our findings demonstrate that image-based lasing analysis is more sensitive to dynamic changes than fluorescence analysis, paving the way for high-throughput on-chip laser analysis of living organisms. Agency for Science, Technology and Research (A*STAR) Nanyang Technological University This research is supported by A*STAR under its AME IRG Grant (project no. A2084c0063). We would like to thank the lab support from Centre of Bio-Devices and Bioinformatics and Internal grant NAP SUG-M4082308.040 from NTU.

Graphene field-effect transistors (GFETs) are suitable building blocks for high-performance electrical biosensors, because graphene inherently exhibits a strong response to charged biomolecules on its surface. However, achieving ultralow limit-of-detection (LoD) is limited by sensor response time and screening effect. Herein, we demonstrate that the detection limit of GFET biosensors can be improved significantly by decorating the uncovered graphene sensor area with carbon dots (CDs). The developed CDs-GFET biosensors used for exosome detection exhibited higher sensitivity, faster response, and three orders of magnitude improvements in the LoD compared with nondecorated GFET biosensors. A LoD down to 100 particles/μL was achieved with CDs-GFET sensor for exosome detection with the capability for further improvements. The results were further supported by atomic force microscopy (AFM) and fluorescent microscopy measurements. The high-performance CDs-GFET biosensors will aid the development of an ultrahigh sensitivity biosensing platform based on graphene for rapid and early diagnosis of diseases.

A new X-ray absorption spectroscopy (XAS) beamline is currently under construction at a bending magnet of the National Synchrotron Radiation Centre SOLARIS. The front end of this beamline was installed in April 2020. This beamline has a few outstanding characteristic features: The monochromator is a fixed exit beam Lemmonier type monochromator allowing to cover the pursued energy range (1 keV to ~15 keV) with 3 sets of crystals: KAP (100) + multilayer, InSb (111) and Ge (220). The monochromator is a high vacuum system allowing the change of crystals in less than an hour. In order to minimize absorption of photons no windows will be installed in the beamline down to the monochromator, and just one thin polypropylene window will be used for separating the vacuum of the monochromator from the ionization chambers and the sample chamber. A special differential ion pump will be installed to maintain the pressure difference of four orders of magnitude between the storage ring and the monochromator. As SOLARIS is a low energy machine, the beamline can be built without any radiation safety hutches without exceeding the strict low radiation safety levels. The straightforward design of the beamline without additional optical elements, its compact overall dimensions and an easy to handle monochromator make this beamline especially user friendly. In combination with the characteristics of the 1.5 GeV SOLARIS storage ring this beamline will be specifically attractive for the tender X-ray range, i.e. the K-edges of important elements such as P, S, Si, Al and Mg.

We introduce a novel and sensitive ns-resolved atomic magnetometer, which is at least three orders of magnitude faster than conventional magnetometers. We use the magnetic field dependence of the hyperfine beating of high-density spin-polarized H atoms, produced from the rapid photodissociation of HCl gas with sub-ns laser pulses and measured with a pick-up coil, to demonstrate ns-resolved magnetometry, and project sensitivity of a few nT for a spin-projection-limited sensor with 10 nl measurement volume after 1 ns measurement time. The magnetometer will allow ultrafast continuous B-field measurements in many fields, including spin chemistry, spin physics, and plasma physics.

Objective. The article deals with the formation of cost-effective light transistors for creating high-speed energy-efficient computer structures that can solve numerous problems with high speed and accuracy. For this purpose, various types of semiconductor structures are used that can emit and absorb photons for receiving and transmitting digital information.Methods. The use of mirror electrodes allows for repeated re-reflection of the generated photons inside the light transistor to recover all the generated energy into electricity. This increases the energy efficiency of the transistor as a whole and allows implementing computer devices with high efficiency in solving various tasks.Results. Most of the useful energy of the information signal is transferred from one electrode to another, and the movement has a higher speed due to the use of photons, rather than drifting electrons, and this indirectly increases the speed of the light transistor by several orders of magnitude and effectively solves the problem of implementing more powerful and high-speed transistors with greater economic benefits.Conclusion. Prospects for the implementation of high-speed energy-efficient computer structures based on both bipolar transistors and unipolar transistors, as well as thyristors, lasers, and other semiconductor components in light-emitting structures have been developed.

The endurance of a Mo/Hf0.3Zr0.7O2/Si capacitor was improved up to 109 cycles by using a Ti layer formed prior to the atomic layer deposition of a Hf0.3Zr0.7O2 film to avoid direct exposure of Si to ozone with resulting trap density decrease.

Nonlinear diffraction of a plane electromagnetic wave from multilayer nonlinear metasurfaces consisting of double-period lattices of rectangular finite-length graphene ribbons on dielectric spacer layers is investigated in the terahertz (THz) frequency range. An increase in the third-harmonic generation efficiency by several orders of magnitude at the surface plasmon–polariton resonance frequencies is demonstrated. It is demonstrated that the third-harmonic frequency can be controlled by dynamic tuning of chemical potential without changing geometry or dimensions of the graphene metasurface.

Control of conductance through a single molecule via alternating anchoring points provides a unique perspective to design single-molecule electronic devices. A high conductance difference among different states is essential for a single-molecule electronic device, which is challenging due to restriction of the structural changes in single-molecule junctions. Here, tetraphenylethylene derivatives with multiple anchoring sites are designed and synthesized to investigate single-molecule conductance using the scanning tunneling microscope break junction (STM-BJ) technique. In the break-junction cycle process, connection conformations with different anchor sites have been achieved reversibly to switch single-molecule conductance using the STM-BJ technique. Through mechanical control, these multi-anchored single-molecule junctions can achieve up to three conductance switching cycles, and the variation in conductance reaches up to four orders of magnitude. Theoretical calculations reveal that the conductance change originates from the different connecting sites and the different anchored configurations of single-molecule junctions provide a significantly different transmission. Our findings provide a reliable strategy to manipulate the mechanical switching and shed light on investigating the intrinsic charge transport of multi-anchored molecules.

Hybrid quantum optomechanical systems offer an interface between a single two-level system and a macroscopical mechanical degree of freedom. In this work, we build a hybrid system made of a vibrating microwire coupled to a single semiconductor quantum dot (QD) via material strain. It was shown a few years ago, that the QD excitonic transition energy can thus be modulated by the microwire motion. We demonstrate here the reverse effect, whereby the wire is set in motion by the resonant drive of a single QD exciton with a laser modulated at the mechanical frequency. The resulting driving force is found to be almost 3 orders of magnitude larger than radiation pressure. From a fundamental aspect, this state dependent force offers a convenient strategy to map the QD quantum state onto a mechanical degree of freedom., Comment: 16 pages, 12 figures

Optical immunoassays require measurement systems capable of distinguishing the light from the laser source, used to illuminate the assay, from the light generated by the particles contained within the assay itself (fluorescence). The main challenge is that the light used to excite the sample is several orders of magnitude more intense than that generated by fluorescence. Usually, single junction photodiodes and optical filters are used. The sensitivity of these schemes is limited by the filter performance. In this work, the design of a CMOS integrated circuit including buried double junction photodiodes (BDJ) is presented. This approach allows the measurement of both light sources simultaneously. From simulations, it is shown that this integrated circuit with BDJ would achieve a better detection limit than the scheme based on single-junction photodiodes of equivalent silicon area. Furthermore, integrating the photodetectors and the reading circuit on the same chip would make the system suitable to be used in biomedical applications such as Point-of-Care (POC) devices., Los inmunoensayos ópticos requieren de sistemas de medición capaces de distinguir la luz de la fuente láser, utilizada para iluminar el ensayo, de aquella generada por las partículas contenidas en el mismo (fluorescencia). El principal desafío es que la luz usada para excitar la muestra es varios órdenes de magnitud más intensa que la generada por fluorescencia. Usualmente, se utilizan filtros ópticos y fotodiodos de juntura simple. La sensibilidad de estos esquemas se encuentra limitada por el desempeño del filtro. En este trabajo se presenta el diseño de un circuito integrado de lectura que incorpora fotodiodos de doble juntura, lo que permite la medición de ambas fuentes de luz en simultáneo. A partir de simulaciones, se demuestra que este enfoque lograría un mejor límite de detección que el esquema basado en fotodiodos de juntura simple de igual área. Además, la integración del circuito de lectura y los fotoreceptores en un mismo chip, favorecería la miniaturización y portabilidad del sistema para aplicaciones biomédicas como en dispositivos Point-of-Care (POC).

A concept of the optimal design of a silicon waveguide based on optically coupled Mie-resonant nanoantennas for efficient inputting of light from point emitters associated with excitons localized at defects in a thin InSe film is proposed. Numerical calculations demonstrate that the efficiency of coupling between a dipole emitter and a resonant silicon waveguide is four orders of magnitude greater than that for a conventional ridge waveguide.

Experimental results of measuring the threshold power density of stimulated emission in coumarin-30 dye solutions with ZnO nanoparticles upon irradiation with femtosecond laser pulses are presented. It is shown that the stimulated emission thresholds of coumarin-30 dye solutions with incorporated ZnO nanoparticles upon irradiation with femtosecond laser pulses are approximately by 3 orders of magnitude higher than the stimulated emission thresholds of coumarin-30 dye solutions with incorporated ZnO nanoparticles irradiated with nanosecond laser pulses.

The development of high-performance glucose sensors is an urgent need, especially for diabetes mellitus diagnosis. However, the glucose monitoring is conventionally operated in an invasive finger-prick manner and their noninvasive alternatives largely suffered from the relatively poor sensitivity, selectivity, and stability, resulted from the lack of robust and efficient catalysts. In this paper, we design a concave shaped nitrogen-doped carbon framework embellished with single Co site catalyst (Co SSC) by selectively controlling the etching rate on different facet of carbon substrate, which is beneficial to the diffusion and contact of analyte. The Co SSC prompts a significant improvement in the sensitivity of the solution-gated graphene transistor (SGGT) devices, with three orders of magnitude better than those of SGGT devices without catalysts. Our findings expand the field of single site catalyst in the application of biosensors, diabetes diagnostics and personalized health-care monitoring.

The efficiency of the laser-induced desorption method as a detector of hydrogen isotopes under pulsed laser irradiation (wavelength 1064 nm, 100 mJ, duration 10 ns) for different power densities of incident radiation on deuterium-saturated thin titanium films was investigated. When the power flow density increases by 16 times, the intensity of the thermal desorption peak increases by more than 2 orders of magnitude. Long-term repeated irradiation of the surface does not lead to significant depletion of the content of hydrogen isotopes in the studied layers, allowing their further ex-situ analysis.

Experimental results showed that the effective thermal conductivity of silicon nanowire is smaller than the bulk thermal conductivity, while that of carbon nanotube (CNT) is usually much larger than its bulk counterpart. In order to resolve this paradox, a nonlocal heat conduction model for one-dimensional materials is proposed. This nonlocal model indicates that the different heat conduction boundary conditions of silicon nanowire and CNT lead to the different behaviour of their thermal conductivities in comparison with their bulk counterparts. Furthermore, the nonlocal effect of heat flux on the surfaces of the CNT makes the thermal conductivity of the single-wall CNT more than seven orders of magnitude higher than its bulk thermal conductivity. The thermal conductivities of the single-wall and multi-wall CNTs obtained by using the nonlocal model show an agreement with the experimental ones.

Atomic force microscopy is employed in the experimental study of specific features of the field emission of electrons from a single silicon needle-type cathode to quasi-vacuum (air). Noncontact regime of the atomic force microscopy is used to measure the I–V characteristics of a single cathode with nanometer-scale tip radius at distances of 10 and 20 nm between the cathode tip and the measurement probe. Electric field distributions are simulated for both surface of the tip of a single cathode and tip surfaces of single cathodes in an array, and the results are used to theoretically estimate electric field enhancement versus cathode–probe distance. It is shown that the enhancement factor calculated from the experimental I–V characteristics in the Fowler–Nordheim coordinates is greater than the result of theoretical calculations by several orders of magnitude. This circumstance indicates that additional quantum dimensional effects that play an important role in the generation of the electron emission current in the nanoscale gap must be taken into account.

Graphene foam (GF)—a three-dimensional network of hollow graphene branches—is a highly attractive material for diverse applications. However, to date, the heat dissipation characteristics of GFs have not been characterized. To fill this gap, we synthesized GF devices, subjected them to high temperatures, and investigated their thermal behavior by using infrared microthermography. We find that while the convective area of GF devices is comparable to that of bulk materials (such as metals), the coefficient of convection of these devices is several orders of magnitude higher than that of metals. In addition, the GF devices showed a reproducible thermal behavior, which we attribute to negligible temperature-induced morphological changes (as confirmed by Raman analysis). Taken together, our findings suggest GF as a promising candidate material for advanced cooling applications where efficient heat dissipation is needed, e.g., in electrical circuits.

A broadband photodetector with high performance is highly desirable for the optoelectric and sensing application. Herein, we report a "photo-thermo-electric" (PTE) detector based on an ultrathin SnTe film. The (001)-oriented SnTe films with the wafer size scale are epitaxially grown on the surface of sodium chloride crystals by a scalable sputtering method. Due to the giant PTE effect under laser spot excitation on the asymmetric position between two terminals, a built-in electrical field is produced to drive bulk carriers for a self-powered photodetector, leading to a broad spectral response in the wavelength range from 404 nm to 10.6 μm far beyond the limitation of the energy band gap. Significantly, the photodetector displays a high on/off photoswitching ratio of over 105 with a suppressed dark current, which is 4-5 orders of magnitude higher than that of other reported SnTe-based detectors. Under zero external bias, the device yields the highest detectivity of ∼1.3 × 1010 cm Hz1/2 W-1 with a corresponding responsivity of ∼3.9 mA W-1 and short rising/falling times of ∼78/84 ms. Furthermore, the photodetector transferred onto the flexible template exhibits excellent mechanical flexibility over 300 bending cycles. These findings offer feasible strategies toward designing and developing low-power-consumption wearable optoelectronics with competitive performance.

In this paper, three dimensional spherical magnetic field coils are proposed and optimized for atomic sensors that require highly uniform magnetic field coils within a limited volume. The design objective of the uniform coil is transformed into a nonlinear optimization model with constraints, which is solved by combining with the particle swarm optimization algorithm. Compared with the traditional cylindrical tri-axial magnetic field coil system whose volume is limited by the aspect ratio of the coil structure, the three dimensional spherical coils not only effectively reduce the volume but also provide consistent magnetic field performance in the three coordinate axis directions. It is of great significance to the miniaturization of atomic sensors. The theoretical calculation shows that the uniformity of spherical coil is improved by about 2 to 3 orders of magnitude compared with the Lee-Whiting coil and the saddle coil. The measurements show that the magnetic field uniformity of our design reached $1.5\times 10^{-4}$ along the ${z}$ -axis within a range of $\pm 0.25{R}$ . The actual magnetic field distribution is basically consistent with the theory. However, due to the limited processing and experimental conditions, the actual magnetic field uniformity is 1 to 2 orders of magnitude lower than the theory.

Overcoming the sub-5 nm gate length limit and decreasing the power dissipation are two main objects in the electronics research field. Besides advanced engineering techniques, considering new material systems may be helpful. Here, we demonstrate two-dimensional (2D) subthermionic field-effect transistors (FETs) with sub-5 nm gate lengths based on ferroelectric (FE) van der Waals heterostructures (vdWHs). The FE vdWHs are composed of graphene, MoS2, and CuInP2S6 acting as 2D contacts, channels, and ferroelectric dielectric layers, respectively. We first show that the as-fabricated long-channel device exhibits nearly hysteresis-free subthermionic switching over three orders of magnitude of drain current at room temperature. Further, we fabricate short-channel subthermionic FETs using metallic carbon nanotubes as effective gate terminals. A typical device shows subthermionic switching over five-to-six orders of magnitude of drain current with a minimum subthreshold swing of 6.1 mV/dec at room temperature. Our results indicate that 2D materials system is promising for advanced highly-integrated energy-efficient electronic devices.

Terahertz (THz) electromagnetic waves strongly interact with complex molecules, making THz spectroscopy a promising tool for high-sensitivity molecular detection, especially for biomedical applications. Metamaterials are typically used for enhancing THz-molecule interactions to achieve higher sensitivities. However, a primary challenge in THz molecular sensing based on metallic metamaterials is the limited tunability of optical constants of metals. Here, we present an ultrahigh-sensitivity molecular sensor based on carbon nanotube (CNT) THz metamaterials. The sensor, consisting of a CNT cut-wire array on a Si substrate prepared by a novel two-step method, exhibits a reflectance resonance whose frequency strongly varies with the substrate composition, geometries of periodic arrays, and analyte composition. We used this sensor to detect glucose, lactose, and chlorpyrifos-methyl molecules, achieving limit-of-detection values of 30, 40, and 10 ng/mL (S/N = 3), respectively, higher than that of metallic metamaterials by 2 orders of magnitude. We attribute this ultrahigh sensitivity to the high conductivity of CNTs and the efficient adsorption of the target analyte by CNTs through van der Waals forces and π-π stacking. These easy-to-fabricate CNT-based THz metamaterials pave the way for versatile and reliable ultrahigh-sensitivity THz molecular detection.

Memristor devices that can operate at high speed with high density and nonvolatile capabilities have great potential for the development of high data storage and robust wearable devices. However, in real-time, the performance of memristors is challenged by their instability toward harsh working conditions such as high temperature, extreme humidity, photo irradiation, and mechanical bending. Herein, we introduce a TaOx/AlN-based flexible and transparent memristor device having stable endurance under extreme 2 mm bending (for more than 107 cycles) with an ON/OFF ratio of more than 2 orders of magnitude at 25 ns rapid switching. This device exhibits excellent flexibility under extreme bending conditions (bending radius of 2 mm) even with intense ultraviolet (UV) radiation. A thin AlN insertion layer having low dielectric and high thermal conductivity plays a crucial role in improving the switching stability and device flexibility. In particular, the devices exhibit excellent minimum switching fluctuations under UV irradiation, >106 s nonvolatility retention at high temperature (135 °C), various gas ambient, and damp heat test (humidity 95.5%, 83 °C) because of the indium metal drift during the switching process and high bonding energy of Ta–O. Most importantly, direct observation of indium metal strongly anchored in the TaOx switching layer during the switching process is reported for the first time via transmission electron microscopy, which provides clear insights into the switching phenomenon. Furthermore, the results of electrical and material analyses explain that our facile device design has excellent potential for wearable and aerospace applications.

We report an ambipolar phototransistor using the organic–inorganic hybrid perovskite, CH3NH3PbI3 [methylammonium lead iodide (MAPbI3)]. The high iconicity of MAPbI3 leads to intrinsic p-type and n-type self-doping, which enables simultaneous or selective hole and/or electron transport in a single device, depending on the bias conditions. Under white light illumination, both hole and electron current increase by four orders of magnitude and the dark characteristics recover completely and immediately after turning off the light source. In addition, the photosensitivity can be controlled by compositional ratio (MAI:PbI2) and the thickness of the MAPbI3 film. Moreover, the hole current shows higher responsivity and shorter response time (0.62 A/W and 100 ms) compared with electron current (0.20 A/W and 200 ms), resulting in respective photodetectivity values of $6.87\times 10^{15}$ and $1.33\times 10^{15}$ Jones. These photodetectivities are among the highest reported, making the phototransistors reported herein suitable for simple and cost-effective optoelectronics.

A combination of conventional calorimetry, ultra-fast scanning calorimetry and resistive heating gives access to heating rates exceeding 6 orders of magnitude allowing to probe crystallization kinetics and mechanisms in a Cu-Zr-Al metallic glass. Continuous-heating-transformation and double-peak time-temperature-transformation diagrams are constructed and related to the formation of glass–crystal composites with enhanced ductility. The metastable B2-CuZr phase becomes dominantly formed at a heating rate of ~102 K s−1 and higher. A critical heating rate to bypass crystallization is ~10,000 K s−1. For isothermal annealing at >850 K, only one crystallization event is detected; for lower temperatures, a complex two-step transformation occurs.

Electron-beam irradiation (EBI) is an effective approach to engineer defects for two-dimensional (2D) materials. However, a detailed understanding of the effects of EBI on charge transport of 2D materials is still lacking. Herein, the value of source-drain current of monolayer MoS2 transistors can be largely improved by about 3 orders of magnitude under EBI, from 5 nA to 24.6 μA at 2 V bias voltage. In addition, a room-temperature mobility (μ) as high as ~ 83 cm2 V−1 s−1 was achieved when the device was irradiated for 80 s with a 10 kV accelerating voltage (~ 5.5% sulphur vacancies), far exceeding (about 80 times) that of the untreated device. The improvements of electrical properties after EBI are mainly attributed to the introduction of electrons and the enhanced charge transport channels. The charge transport behaviour under EBI exhibits variable range hopping associated with temperature. Our findings provide an avenue for building high performance electronics based on 2D materials.

Application of conducting ferroelectric domain walls (DW) as functional elements may facilitate development of conceptually new resistive switching devices. In a conventional approach, several orders of magnitude change in resistance can be achieved by controlling the DWs density using super-coercive voltage. However, a deleterious characteristic of this approach is high-energy cost of polarization reversal due to high leakage current. Here, we demonstrate a new approach based on tuning the conductivity of DWs themselves rather than on domain rearrangement. Using LiNbO3 capacitors with graphene, we show that resistance of a device set to a polydomain state can be continuously tuned by application of sub-coercive voltage. The tuning mechanism is based on the reversible transition between the conducting and insulating states of DWs. The developed approach allows an energy-efficient control of resistance without the need for domain structure modification. The developed memristive devices are promising for multi-level memories and neuromorphic computing applications.

The description of detectors based on measuring the secondary-emission current and results of their tests are presented. Multichannel profilometers with a range of n × 103 to 109 ions/(cm2 s) have been created. This range is largely overlapped with the range from a few units to 106 ions/(cm2 s), which is characteristic of scintillation and semiconductor detectors. Current profilometers are used in the region of the overlap to monitor their degradation under exposure to the beam. The current profilometers are used in the transit of low-intensity beams, and their sensitivity is higher than the sensitivity of Al2O3 phosphors and Faraday cups by four orders of magnitude. A three-lamel probe has been created based on the secondary emission to measure the current of the internal accelerator beam with a lower-range value of 0.1 pA.

We have studied the response of graphene-film-based chips on SiC substrates (the relative change in the chip resistance) to coming into contact with fluorescein (C20H12O5) in a wide range of its concentrations in a phosphate-buffered saline solution: from 1 × 10–3 to 1 × 104 ng/mL (seven orders of magnitude). Fluorescein detection seems to be a simple and cheap model experiment to study the sensory ability of graphene in the way of biochips manufacturing. It has been shown that chips with wide terraces on a surface with a step width of about 1000 nm and heights of up to 5 nm made it possible to construct the calibration dependences of chip response on fluorescein concentration.

Low-frequency noise is a key performance-limiting factor in almost all electronic systems. Thanks to its excellent characteristics such as exceptionally high electron mobility, graphene has high potential for future low-noise electronic applications. Here, we present an experimental analysis of low-frequency noise in dual-gate graphene transistors based on chemical vapor-deposited Bernal-stacked bilayer graphene. The fabricated dual-gate bilayer graphene transistors adopt atomic layer-deposited Al2O3 and HfSiO as top-gate and back-gate dielectric, respectively. Our results reveal an obvious M-shape gate-dependent noise behavior which can be well described by a quantitative charge-noise model. The minimal area normalized noise spectral density at 10 Hz reaches as low as about 3 × 10-10 μm2·Hz-1 at room temperature, much lower than the best results reported previously for graphene devices. In addition, the observed noise level further decreases by more than 10 times at temperature of 20 K. Meanwhile, the noise spectral density amplitude can be tuned by more than 2 orders of magnitude at 20 K by dual-gate voltages.

Bioelectronic devices must be fast and sensitive to interact with the rapid, low-amplitude signals generated by neural tissue. They should also be biocompatible and soft, and should exhibit long-term stability in physiologic environments. Here, we develop an enhancement-mode, internal ion-gated organic electrochemical transistor (e-IGT) based on a reversible redox reaction and hydrated ion reservoirs within the conducting polymer channel, which enable long-term stable operation and shortened ion transit time. E-IGT transient responses depend on hole rather than ion mobility, and combine with high transconductance to result in a gain-bandwidth product that is several orders of magnitude above that of other ion-based transistors. We used these transistors to acquire a wide range of electrophysiological signals, including in vivo recording of neural action potentials, and to create soft, biocompatible, long-term implantable neural processing units for the real-time detection of epileptic discharges. E-IGTs offer a safe, reliable and high-performance building block for chronically implanted bioelectronics, with a spatiotemporal resolution at the scale of individual neurons.