Electrical Crosstalk Research Articles

Zero-bias 32 Gb/s evanescently coupled InGaAs/InP UTC-PDs

We report the design and fabrication of high speed evanescently coupled InGaAs/InP uni-traveling-carrier-photodiodes (UTC-PDs). A self-aligned passive waveguide is integrated with the PDs by a simple fabrication procedure. Open eye diagrams at 32 Gb/s under zero bias are demonstrated for the first time, to the best of our knowledge, from evanescently or edge coupled InP based PDs, which are easier to be integrated with other optical components than surface illuminated PDs. When used for photonic integrated circuits (PICs) applications, our PDs help to lower the electrical cross talk and power consumption of PICs chips.

On-Chip Feedthrough Cancellation Methods for Microfabricated AFM Cantilevers With Integrated Piezoelectric Transducers

Active microcantilevers with on-chip sensing and actuation capabilities provide significant advantages in tapping-mode atomic force microscopy. The collocated transduction in active cantilevers enables effective control of their dynamics, allowing for the modification of the quality ( $Q$ ) factor and operation at higher flexural modes to obtain higher scan rates. However, having closely spaced transducers in dynamic applications often results in electrical crosstalk from the actuation signal to the sensor output. As a result, the dynamic response of the cantilever becomes heavily dominated by this feedthrough, making the use of on-chip transduction impractical for atomic force microscope (AFM) imaging without cancelling this undesired effect. In this paper, we propose two on-chip feedthrough cancellation methods based on pseudo-differential actuation and differential sensing concepts. The implementation of the methods is demonstrated by the use of two microfabricated cantilevers with separate piezoelectric sensors and actuators. Following the cancellation of the feedthrough, both cantilevers are successfully employed for AFM imaging using the on-chip transducers for actuation and deflection sensing. [2017-0101]

Visual Prosthesis: Interfacing Stimulating Electrodes with Retinal Neurons to Restore Vision.

The bypassing of degenerated photoreceptors using retinal neurostimulators is helping the blind to recover functional vision. Researchers are investigating new ways to improve visual percepts elicited by these means as the vision produced by these early devices remain rudimentary. However, several factors are hampering the progression of bionic technologies: the charge injection limits of metallic electrodes, the mechanical mismatch between excitable tissue and the stimulating elements, neural and electric crosstalk, the physical size of the implanted devices, and the inability to selectively activate different types of retinal neurons. Electrochemical and mechanical limitations are being addressed by the application of electromaterials such as conducting polymers, carbon nanotubes and nanocrystalline diamonds, among other biomaterials, to electrical neuromodulation. In addition, the use of synthetic hydrogels and cell-laden biomaterials is promising better interfaces, as it opens a door to establishing synaptic connections between the electrode material and the excitable cells. Finally, new electrostimulation approaches relying on the use of high-frequency stimulation and field overlapping techniques are being developed to better replicate the neural code of the retina. All these elements combined will bring bionic vision beyond its present state and into the realm of a viable, mainstream therapy for vision loss.

Why build an integrated EEG-NIRS? About the advantages of hybrid bio-acquisition hardware.

In medical applications, neuroscience and brain-computer interface research, bimodal acquisition of brain activity using Electroencephalography (EEG) and functional Near Infrared Spectroscopy (fNIRS) is at the moment achieved by combining separate commercial devices. We have investigated quantitatively whether dedicated hybrid systems exhibit more advantageous properties. We studied intermodality electrical crosstalk and timing jitter in two separate and one hybrid EEG-NIRS acquisition device. Analysis revealed significantly higher impact of electrical NIRS current crosstalk into the EEG inputs and timing jitters between EEG-NIRS markers in separate devices compared to the hybrid system. The results support hybrid acquisition systems to be advantageous in setups that require high performance in timing and signal quality.

Electric Crosstalk Effect in Valence Change Resistive Random Access Memory

Electric crosstalk phenomenon in valence change resistive switching memory (VCM) is systematically investigated. When a voltage is applied on the VCM device, an electric field is formed in the isolated region between the devices, which causes the oxygen vacancies in conductive filaments (CFs) to drift apart, leading to a consequent resistance degradation of the neighboring devices. The effects of distance between memory cells, electrodes widths and physical dimensions of CFs on the memory performance are investigated in this work. Furthermore, the strategies to mitigate electric crosstalk effects are developed. According to the simulation results, the crosstalk phenomenon can become more severe as the distance between memory cells or the electrode width decreases. In order to optimize the device performance, it is helpful to control the location of the break points of CFs in the device close to the top electrode. Alternatively, taking the integration density into account, switching materials with a small field accelerated parameter can also contribute to obtaining a stable performance.

Electrical cross-talk subtraction for free-field reciprocity calibration of half-inch laboratory standard microphones.

This paper presents a procedure for free-field calibration of half-inch laboratory standard microphones by reciprocity that allows the identification and removal of the electrical cross-talk, multiple backscattering, reflections, noise, and all harmonic distortion components when measuring the electrical transfer impedance between the microphones. Initially, the difficulties of free-field calibration of condenser microphones by the reciprocity method are pointed out and the state of art is summarized. Following, the proposed procedure, which allows determining microphone sensitivities in the frequency range from 1 kHz to 40 kHz, is described: The cross-talk is removed by subtraction while multiple backscattering, reflections, noise and all harmonic distortion components are removed by a time-selective technique. Measurements and results are presented and discussed. A comparison between the results obtained by the proposed procedure and the pressure field calibration results corrected to free-field shows the efficiency and accuracy of the technique.

Near surface ultrasonic imaging

Ultrasonic phased arrays offer excellent performance for detecting and classifying defects; however when inspecting near the array, there is typically a deadzone where electrical cross talk saturates the response making it impossible to measure. In many situations this can be mitigated through the use of a physical standoff, however for permanently installed systems or in situ inspection of components in access restricted areas such as gas turbines such a solution is impossible. In addition, such a standoff typically reduces the amplitude of the received signals degrading the signal to noise ratio (SNR). This paper reports on an approach that allows ultrasonic measurements to be made of the near surface region. Specifically by measuring the diffuse response of the system it is possible to reconstruct the greens function between any pair of transducers. As this is created from data that is not saturated there is no deadzone in the resulting image. When combined with advanced sampling techniques using hadamard coding the region immediately in front of the array can be imaged with performance similar to that seen in the bulk material despite this reconstruction approach. In this paper, the reconstruction and sampling technique are explained and demonstrated with images shown for defects within 0.5 mm of the sample surface in both aluminium and composite components. The advantages of the sampling approach are shown for immersion coupled measurements to demonstrate the SNR gains achievable.

Microfabrication and Characterization of Concentric Nanodes for Brain Chemical Sensing

Understanding the function of human brain is one of the most scientific challenges of the 21st century. Recent studies show the critical role of neurochemicals in several brain disorders such as Epilepsy, Parkinson’s Disease, Alzheimer’s disease and Schizophrenia. Developing advanced chemical sensor technologies that can detect multiple neurochemicals, neurotoxins and local field potentials with high spatial-temporal resolution is urgently needed to better understand the underlying mechanisms. Current chemical microsensors foul quickly and lack sensitivity in long-term use. They also are bulky and lack multiplexing, multimodal capability. In recent times, there is an enormous interest in the use of band, disc and hemispherical nanoelectrodes for novel electroanalytical applications. Albeit their advantages in terms of enhanced analyte transport, low charging currents and high signal-to-noise ratio, they do not provide a 3D electrode geometry that are more suitable for interrogating cells and tissues and are difficult to fabricate multiple nanoelectrodes onto a single cylindrical probe. In this work, we design, fabricate and characterize a novel ring-shaped nanoelectrode “nanode” for brain chemicals of importance. Gold nanodes are micro fabricated on to silicon micropillars and are characterized using SEM, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The nanode’s general electrochemical behavior will be studied in standard redox species. We report the effect of Atomic Layer Deposition coated passivation layers and their thickness on electrical cross talk. Using multiple concentric nanodes (e.g. Au, Pt and boron-doped nano diamond), improvements in chemical signal amplification from dopamine and lead will be discussed.

宽谱光源对CMOS阵列电串扰的影响

宽谱光源对CMOS阵列电串扰的影响

宽谱光源对CMOS阵列电串扰的影响

宽谱光源对CMOS阵列电串扰的影响

Organic Transistor Arrays Integrated with Finger-Powered Microfluidics for Multianalyte Saliva Testing.

A compact multianalyte biosensing platform is reported, composed of an organic electrochemical transistor (OECT) microarray integrated with a pumpless "finger-powered" microfluidic, for quantitative screening of glucose, lactate, and cholesterol levels. A biofunctionalization method is designed, which provides selectivity towards specific metabolites as well as minimization of any background interference. In addition, a simple method is developed to facilitate multi-analyte sensing and avoid electrical crosstalk between the different transistors by electrically isolating the individual devices. The resulting biosensing platform, verified using human samples, offers the possibility to be used in easy-to-obtain biofluids with low abundance metabolites, such as saliva. Based on our proposed method, other types of enzymatic biosensors can be integrated into the array to achieve multiplexed, noninvasive, personalized point-of-care diagnostics.

Electrical cross-talk in four-electrode experiments

The subject of this paper is electrical cross-talk, an interference between the current/voltage characteristics of the two working electrodes in four-electrode (generator/collector) systems. Cross-talk arises in electrochemical cells of finite resistance due to the superposition of the electrical fields of the working electrodes, and often causes difficulties in the interpretation of measurement results. In this paper, we present an algorithm for modelling simple generation/collection experiments with a rotating ring–disk electrode (RRDE) immersed into a finite resistance solution of a redox couple. We show that based on the analysis of the Kirchhoff (Laplace) matrix of the simulation mesh, the effect of electrical cross-talk may be accounted for in such experiments. The intensity of cross-talk is found to be heavily influenced by the selection of the reference point for potential measurements; in practice, this is the position of the reference electrode or the tip of the Luggin probe. The devised model is validated by means of a simple and demonstrative experiment.

Performance Degradation of Integrated Optical Modulators Due to Electrical Crosstalk

In this paper, we investigate electrical crosstalk in integrated Mach-Zehnder modulator arrays based on n-doped InP substrate and show that it can be the cause for transmitter performance degradations. In particular, a common ground return path between adjacent modulators can cause high coupling noise up to −20 dB which leads to system power penalties of more than 10 dB at 10 Gb/s OOK modulation. Furthermore, we demonstrate that electrical crosstalk is significantly reduced in the absence of the shared ground and that it varies with modulator separation distance. Experimental results are shown that indicate a crosstalk tolerance of −40 dB for 1 dB power penalty at 10 Gb/s.

The Impact of Interpixel Capacitance in CMOS Detectors on PSF Shapes and Implications for WFIRST

Unlike optical CCDs, near-infrared detectors, which are based on CMOS hybrid readout technology, typically suffer from electrical crosstalk between the pixels. The interpixel capacitance (IPC) responsible for the crosstalk affects the point-spread function (PSF) of the telescope, increasing the size and modifying the shape of all objects in the images while correlating the Poisson noise. Upcoming weak lensing surveys that use these detectors, such as WFIRST, place stringent requirements on the PSF size and shape (and the level at which these are known), which in turn must be translated into requirements on IPC. To facilitate this process, we present a first study of the effect of IPC on WFIRST PSF sizes and shapes. Realistic PSFs are forward-simulated from physical principles for each WFIRST bandpass. We explore how the PSF size and shape depends on the range of IPC coupling with pixels that are connected along an edge or corner; for the expected level of IPC in WFIRST, IPC increases the PSF sizes by ∼5%. We present a linear fitting formula that describes the uncertainty in the PSF size or shape due to uncertainty in the IPC, which could arise for example due to unknown time evolution of IPC as the detectors age or due to spatial variation of IPC across the detector. We also study of the effect of a small anisotropy in the IPC, which further modifies the PSF shapes. Our results are a first, critical step in determining the hardware and characterization requirements for the detectors used in the WFIRST survey.

Low-crosstalk operation of directly modulated DFB laser array TOSA for 112-Gbit/s application.

A directly modulated DFB laser (DML) array transmitter optical sub-assembly (TOSA) operating at 112 Gbit/s was fabricated for the first time. The DML array chip, which was integrated with a GND pad, and the DML array sub-assembly were designed to suppress the adjacent electrical crosstalk of the DML array TOSA. The 3-dB bandwidths of the fabricated TOSA exceeded 18 GHz. The electrical crosstalk of the TOSA was suppressed to less than -20 dB below 18GHz. Under simultaneous 4-channel 28-Gbit/s (112 Gbit/s) operation, the OTU4 mask margins were degraded by a maximum of only 6% compared with those under discrete operation. Error-free transmissions over a 10-km single-mode fiber were demonstrated for all the lanes under 112-Gbit/s operation.

Shielded Coaxial Optrode Arrays for Neurophysiology.

Recent progress in the study of the brain has been greatly facilitated by the development of new tools capable of minimally-invasive, robust coupling to neuronal assemblies. Two prominent examples are the microelectrode array (MEA), which enables electrical signals from large numbers of neurons to be detected and spatiotemporally correlated, and optogenetics, which enables the electrical activity of cells to be controlled with light. In the former case, high spatial density is desirable but, as electrode arrays evolve toward higher density and thus smaller pitch, electrical crosstalk increases. In the latter, finer control over light input is desirable, to enable improved studies of neuroelectronic pathways emanating from specific cell stimulation. Here, we introduce a coaxial electrode architecture that is uniquely suited to address these issues, as it can simultaneously be utilized as an optical waveguide and a shielded electrode in dense arrays. Using optogenetically-transfected cells on a coaxial MEA, we demonstrate the utility of the architecture by recording cellular currents evoked from optical stimulation. We also show the capability for network recording by radiating an area of seven individually-addressed coaxial electrode regions with cultured cells covering a section of the extent.

Microelectromechanical Parallel Scanning Nanoprobes for Nanolithography

This paper presents a new approach and preliminary results for MEMS-enabled low-cost and high throughput parallel scanning probe nanolithography. The proposed approach is based on integrated microelectromechanical systems capable of simultaneous generation of a large number of identical nanoprecision patterns on a substrate. Integration of two-degree-of-freedom MEMS actuators with two-dimensional nanoprobe arrays as well as preliminary results for simultaneous generation of multiple submicrometer patterns using such devices is reported. Electrical cross talk between the fully silicon fabricated actuators along X - and Y -axes has been eliminated by optimizing the design. Scratch marks as narrow as 250 nm and as long as 42 μm have been generated on a thin photoresist layer, which was spin-coated on a silicon substrate using the electrothermal MEMS structure carrying up to 25 nanotips. Furthermore, the submicrometer patterns have been successfully transferred to the underlying silicon substrate via reactive ion etching. Patterns as narrow as 250 nm (∼60 nm in depth) were obtained on the underlying silicon substrate.

Electrical cross-talk in rotating ring–disk experiments

The electrical cross-talk between the two working electrodes of generator/collector systems is investigated. Digital simulations are carried out to model simple collection experiments with a rotating ring–disk electrode (RRDE) immersed into a finite resistance solution of a redox couple, where electrical cross-talk may arise due to the shared current routes of the two working electrodes. Based on the analysis of the Kirchhoff (Laplace) matrix of the simulation mesh it is demonstrated that the cross-talk effect is heavily influenced by the selection of the reference point for potential measurements; in practice this is the position of the reference electrode or the tip of the Luggin probe. The devised model is validated by means of a simple and demonstrative experiment.

A barrier structure optimization for widening processing window in dual-band HgCdTe IRFPAs detectors

Dual-band HgCdTe IRFPAs detectors are one of the most important developing frontiers for 3rd generation IRFPAs detectors. A barrier structure has been implemented in the dual-band HgCdTe detectors to restrain the electrical cross-talk between two layers with different compositions. Moreover, we now reveal another benefit of this barrier structure. This barrier can relieve the critical demands in photo-lithography of the implantation process, which shows great advantages as the dimension of a single element in advanced dual-band IRFPAs detectors is becoming less than 30 μm. When the implantation pattern migrates, the profile of the cavity in the dual-band structure is exposed under implantation. An n-type connection between LW layer and MW layer will be induced. With a modified barrier, the dark current of the MW contact can be reduced to the same order as those with precise implantation.

Optimization of return electrodes in neurostimulating arrays

Objective. High resolution visual prostheses require dense stimulating arrays with localized inputs of individual electrodes. We study the electric field produced by multielectrode arrays in electrolyte to determine an optimal configuration of return electrodes and activation sequence. Approach. To determine the boundary conditions for computation of the electric field in electrolyte, we assessed current dynamics using an equivalent circuit of a multielectrode array with interleaved return electrodes. The electric field modeled with two different boundary conditions derived from the equivalent circuit was then compared to measurements of electric potential in electrolyte. To assess the effect of return electrode configuration on retinal stimulation, we transformed the computed electric fields into retinal response using a model of neural network-mediated stimulation. Main results. Electric currents at the capacitive electrode-electrolyte interface redistribute over time, so that boundary conditions transition from equipotential surfaces at the beginning of the pulse to uniform current density in steady state. Experimental measurements confirmed that, in steady state, the boundary condition corresponds to a uniform current density on electrode surfaces. Arrays with local return electrodes exhibit improved field confinement and can elicit stronger network-mediated retinal response compared to those with a common remote return. Connecting local return electrodes enhances the field penetration depth and allows reducing the return electrode area. Sequential activation of the pixels in large monopolar arrays reduces electrical cross-talk and improves the contrast in pattern stimulation. Significance. Accurate modeling of multielectrode arrays helps optimize the electrode configuration to maximize the spatial resolution, contrast and dynamic range of retinal prostheses.