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The identification and quantification of biomarkers with innovative technologies is an urgent need for the precise diagnosis and follow up of human diseases. Body fluids offer a variety of informative biomarkers, which are traditionally measured with time-consuming and expensive methods. In this context, lateral flow tests (LFTs) represent a rapid and low-cost technology with a sensitivity that is potentially improvable by chemiluminescence biosensing. Here, an LFT based on gold nanoparticles functionalized with antibodies labeled with the enzyme horseradish peroxidase is combined with a lensless biosensor. This biosensor comprises four Silicon Photomultipliers (SiPM) coupled in close proximity to the LFT strip. Microfluidics for liquid handling complete the system. The development and the setup of the biosensor is carefully described and characterized. C-reactive protein was selected as a proof-of-concept biomarker to define the limit of detection, which resulted in about 0.8 pM when gold nanoparticles were used. The rapid readout (less than 5 min) and the absence of sample preparation make this biosensor promising for the direct and fast detection of human biomarkers. [ABSTRACT FROM AUTHOR]

We assessed the accuracy of a prototype radiation detector with a built in CMOS amplifier for use in dosimetry for high dose rate brachytherapy. The detectors were fabricated on two substrates of epitaxial high resistivity silicon. The radiation detection performance of prototypes has been tested by ion beam induced charge (IBIC) microscopy using a 5.5 MeV alpha particle microbeam. We also carried out the HDR Ir-192 radiation source tracking at different depths and angular dose dependence in a water equivalent phantom. The detectors show sensitivities spanning from (5.8 ± 0.021) × 10−8 to (3.6 ± 0.14) × 10−8 nC Gy−1 mCi−1 mm−2. The depth variation of the dose is within 5% with that calculated by TG-43. Higher discrepancies are recorded for 2 mm and 7 mm depths due to the scattering of secondary particles and the perturbation of the radiation field induced in the ceramic/golden package. Dwell positions and dwell time are reconstructed within ±1 mm and 20 ms, respectively. The prototype detectors provide an unprecedented sensitivity thanks to its monolithic amplification stage. Future investigation of this technology will include the optimisation of the packaging technique. [ABSTRACT FROM AUTHOR]

Creating conductive biocompatible coatings with enhanced stability and adhesion can be achieved with cold plasma-assisted processes that provide surface modification, and assisted polymerization at mild conditions and room temperature. Herein, a novel method is reported for the controlled deposition of conductive polymer poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) on substrates with different characteristics: polyethylene terephthalate, poly(dimethylsiloxane), and soda-lime glass. The plasma deposited PEDOT:PSS films are studied by atomic force microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy, and tested for stability and adhesion. The electrical resistance is obtained by a four-point probe station to investigate the influence of plasma reaction and etching mechanism on the reproducibility of the electrical parameters. The proposed method is also successfully developed for the deposition of stacked layers structures, with the aim to design basic passive electrical components, such as a resistor or a capacitor. The possibility of realizing complex shapes by selective area deposition can enable the realization of advanced biosensor devices. [ABSTRACT FROM AUTHOR]

Two-dimensional transition metal dichalcogenides (TMDCs) are demonstrated to be appealing semiconductors for optoelectronic applications, thanks to their remarkable properties in the ultraviolet-visible spectral range. Interestingly, TMDCs have not yet been characterized when exposed to x rays, although they would be ideal candidates for optoelectronic applications in this spectral range. They benefit from the high cross section of the constituent heavy atoms, while keeping the absorption very low, due to the ultrathin structure of the film. This encourages the development of photodetectors based on TMDCs for several applications dealing with x rays, such as radioprotection, medical treatments, and diagnosis. Given the atomic thickness of TMDCs, they can be expected to perform well at low dose measurements with minimal perturbation of the radiation beam, which is required for in vivo applications. In this paper, the use of TMDCs as active materials for direct x-ray detection is demonstrated, using a photodetector based on a MoS2 monolayer (1L-MoS2). The detector shows a response to x rays in the range of 101–102 keV, at dose rates as low as fractions of mGy/s. The sensitivity of 1L-MoS2 reaches values in the range of 108–109µC Gy−1 cm−3, overcoming the values reported for most of the organic and inorganic materials. To improve the x-ray photoresponse even further, the 1L-MoS2 was coupled with a polymeric film integrating a scintillator based on terbium-doped gadolinium oxysulfide (Gd2O2S:Tb). The resulting signal was three times larger, enabled by the indirect x ray to visible photoconversion mechanism. This paper might pave the way toward the production of ultrathin real-time dosimeters for in vivo applications. [ABSTRACT FROM AUTHOR]

Currently, optical sensors based on molecularly imprinted polymers (MIPs) have been attracting significant interest. MIP sensing relies on the combination of the MIP's selective capability, which is conveyed to the polymeric material by a template-assisted synthesis, with optical techniques that offer exquisite sensitivity. In this work, we devised an MIP nanoparticle optical sensor for the ultralow detection of serum albumin through time-resolved fluorescence spectroscopy. The Fluo-nanoMIPs (∅~120 nm) were synthetized using fluorescein-O-methacrylate (0.1×, 1×, 10× mol:mol versus template) as an organic fluorescent reporter. The ability of 0.1× and 1×Fluo-nanoMIPs to bind albumin (15 fM–150 nM) was confirmed by fluorescence intensity analyses and isothermal titration calorimetry. The apparent dissociation constant (Kapp) was 30 pM. Conversely, the 10× fluorophore content did not enable monitoring binding. Then, the time-resolved fluorescence spectroscopy of the nanosensors was studied. The 1×Fluo-nanoMIPs showed a decrease in fluorescence lifetime upon binding to albumin (100 fM–150 nM), Kapp = 28 pM, linear dynamic range 3.0–83.5 pM, limit of detection (LOD) 1.26 pM. Selectivity was confirmed testing 1×Fluo-nanoMIPs against competitor proteins. Finally, as a proof of concept, the nanosensors demonstrated detection of the albumin (1.5 nM) spiked in wine samples, suggesting a possible scaling up of the method in monitoring allergens in wines. [ABSTRACT FROM AUTHOR]

A compact probe for charged particle imaging, with potential applications in source activity mapping and radio-guided surgery was designed and tested. The development of this technology holds significant implications for medical imaging, offering healthcare professionals accurate and efficient tools for diagnoses and treatments. To fulfill the portability requirements of these applications, the probe was designed for battery operation and wireless communication with a PC. The core sensor is a dual-layer CMOS SPAD detector, fabricated using 150 nm technology, which uses overlapping cells to produce a coincidence signal and reduce the dark count rate (DCR). The sensor is managed and interfaced with a microcontroller, and custom firmware was developed to facilitate communication with the sensor. The performance of the probe was evaluated by characterizing the on-board SPAD detector in terms of the DCR, and the results were consistent with the characterization measurements taken on the same chip samples using a purposely developed benchtop setup. [ABSTRACT FROM AUTHOR]

Electroadhesion is a suitable technology for developing grippers for applications where fragile, compliant or variable shape objects need to be grabbed and where a retention action is typically preferred to a compression force. This article presents a self-sensing technique for electroadhesive devices (EAD) based on the capacitance measure. Specifically, we demonstrate that measuring the variation of the capacitance between electrodes of an EAD during the adhesion can provide useful information to automatically detect the successful grip of an object and the possible loss of adhesion during manipulation. To this aim, a dedicated electronic circuit is developed that is able to measure capacitance variations while the high voltage required for the adhesion is activated. A test bench characterization is presented to evaluate the self-sensing of capacitance during different states: (1) the EAD is far away from the object to be grasped; (2) the EAD is in contact with the object, but the voltage is not active (i.e., no adhesion); and (3) the EAD is activated and attached to the object. Correlation between the applied voltage, object material and shape and capacitance is made. The self-sensing EAD is then demonstrated in a closed-loop robotic application that employs a robot manipulator arm to pick and place objects of different kinds. [ABSTRACT FROM AUTHOR]

TeraHertz (THz) detection with Field-Effect Transistor-based (FET-based) detectors requires low-noise amplification, which typically involves trade-offs in terms of complexity, power, and area, resulting in severe scalability constraints for pixel integration into imaging arrays. The purpose of this paper is to describe a novel approach, from design to experimental validation, that enables active device-level amplification of the signal generated by a FET detector and converts it to a frequency suitable for digital processing. This has been done by exploiting a Single-Electron Bipolar Avalanche Transistor (SEBAT) to build a low-noise compact front-end circuit. The FET output is connected to the SEBAT forming a circuit element that here is defined as a TeraHertz Single-Electron Transistor (THzSET). The FET generates a detection current when it senses the THz signal; this current is then injected into the SEBAT, which generates an avalanche current pulse for each single electron, achieving a device-level amplification. The avalanche pulse rate is then evaluated from the signal measured at the SEBAT collector, and performing an FFT of the counts-per-second curve over time it is possible to measure the modulated THz signal applied to the device. The obtained Responsivity $\text {R}_{\text {F}}$ and the Noise Equivalent Power NEP are respectively $\frac {\text {4.61Gcps}}{\text {W}}$ and $\frac {\text {88nW}}{\sqrt {\text {Hz}}} $ at 330GHz illumination frequency. This is achieved with sub- $\mu \text{W}$ power consumption and minimal area overhead: indeed, the pixel and the interface have a total area of 0.146mm2, where the antenna area is ${455} \times {320}\mu \text{m}^{{2}}$ and the SEBAT area is ${27} \times {22}\mu \text{m}^{{2}}$. [ABSTRACT FROM AUTHOR]

One of the aspects that semiconductor devices have to cope with in space applications is radiation induced damage. Therefore, radiation hardness studies are crucial for the space missions and a comprehensive on-ground testing of the components needs to be performed aiming at identifying the most radiation tolerant technologies. This paper reports the test results on newly designed and fabricated 8-channel silicon phototransistors arrays, their performance against various layouts designs, and process implementations, and discusses the achieved reliability after exposure to gamma rays, protons radiations, and high-temperature storage at wafer level in the framework of Optoi's aerospace activities. This work was funded by the European Space Agency. The results also represent a complementary analysis aimed at better understanding and interpreting the outcomes of the non-packaged devices. In conclusion, the best combination of design parameters proving the most robust with respect to the others could be selected, being considered satisfactory and acceptable for the next phase of component assessment. [ABSTRACT FROM AUTHOR]

In this work, we propose a prototype of a compact detector assembly capable of discriminating between neutrons and gamma rays, by performing pulse shape analysis. The device takes advantage of recent improvements in silicon photomultiplier (SiPM) technology and the excellent neutron/gamma-ray discrimination capabilities of new plastics and standard liquid scintillators. Our work is focused on the read-out of small-, medium-, and large-sized organic scintillators with large-area SiPM arrays ($4 \times 4$ NUV and RGB-SiPM arrays, 17 mm $\times$ 17 mm). In particular, we used EJ-276 (and its old version EJ-299) and EJ-276G plastic scintillators of several sizes (ranging from 20- to 50-mm diameter) and two large liquid scintillator cells (EJ-301 and EJ-309, 50 mm diameter $\times 50$ mm thickness). Moreover, we show the comparison of neutron/gamma-ray discrimination performance between SiPM and standard photomultiplier read-out configurations. The presented innovative device could be used in different fields, first in fundamental nuclear physics experiments, as an ancillary neutron detector for the active target at the selective production of exotic species (SPES) facility at the Legnaro National Laboratories in Italy. Additionally, it could be used in radiation monitoring applications, as a fast neutron/gamma-ray counter to be embedded in unmanned vehicles for radiation monitoring. [ABSTRACT FROM AUTHOR]

This article presents a fully depleted monolithic active pixel sensor technology compatible with a standard deep submicrometer 110-nm CMOS process. Passive test pixels structures, produced in various flavors, have proved the feasibility of 100- and 300-μm-thick active substrates. Active pixel sensors with monolithically integrated analog and digital electronics, consisting of a 24 × 24 array of pixels with 50-μm pitch, have been shown to be fully functional when operating in the full depletion mode. Characterization results obtained with a proton microbeam and a 55Fe radiation source are presented and discussed. [ABSTRACT FROM AUTHOR]

The growing interest toward the development of high‐Z–sensitized organic scintillators is related with the potential possibility to merge the advantages of organic materials with those of inorganics. In fact, organic plastic scintillators offer large‐area applications and fast response at a low cost, yet their performances for high‐energy photons and charged particles are limited by the poor stopping power related with low‐Z materials. The real‐time optical investigation in terms of steady‐state luminescence spectra of polysiloxane/quantum dot (QD) nanocomposite samples under 2 MeV proton irradiation is presented. Results show an increase in the light yield of the polysiloxane samples embedding QDs up to 8% in comparison with the undoped polymer, paving the way for high‐Z sensitization through QDs in polysiloxane‐based active radiation detection systems. [ABSTRACT FROM AUTHOR]

Reliability is an important consideration during semiconductor technology development, which ensures that the performances of devices, circuits, and systems are maintained over a specified period of time, leading to successful products. Device reliability is at the core of overall product reliability, which continues to remain an important area of research and has attracted the attention of IEEE Transactions on Electron Devices (T-ED) authors and readers throughout the years. Device reliability can be classified into two broad areas: gradual drift of device performance over time or sudden failure, and both are of importance for logic, memory, RF, and power devices. Different aspects of device reliability are usually reported, such as the development of electrical or physical characterization methods, investigation and modeling of a particular phenomenon, impact of material and processes on reliability, and development of reliability tolerant technologies. [ABSTRACT FROM AUTHOR]

The current trend in the design of systems based on CMOS SPADs is to adopt smaller technological nodes, allowing the co-integration of additional electronics for the implementation of complex digital systems on chip. Due to their simplicity, a way to reduce the area occupied by the integrated electronics is the use of passive quenching circuits (PQCs) instead of active (AQCs) or mixed (MQCs) ones. However, the recharge phase in PQCs is slower, so the device can be retriggered before this phase ends. This paper studies the phenomena of afterpulsing and retriggering, depending on the characteristics of the SPADs and the working conditions. In order to do that, a test chip containing SPADs of different size has been characterized in several operating environments. A mathematical model has been proposed for fitting afterpulsing phenomenon. It is shown that retriggering can be also described in terms of this model, suggesting that it is linked to carriers trapped in the shallow levels of the semiconductor and that should be taken into account when considering the total amount of afterpulsing events. [ABSTRACT FROM AUTHOR]

We report on a scintillator-based online detection system for the spectral characterization of polychromatic proton bunches. Using up to nine stacked layers of radiation hard polysiloxane scintillators, coupled to and readout edge-on by a large area pixelated CMOS detector, impinging polychromatic proton bunches were characterized. The energy spectra were reconstructed using calibration data and simulated using Monte-Carlo simulations. Despite the scintillator stack showed some problems like thickness inhomogeneities and unequal layer coupling, the prototype allows to obtain a first estimate of the energy spectrum of proton beams. [ABSTRACT FROM AUTHOR]

We present a field-programmable gate array (FPGA) implementation of a time-to-digital converter (TDC) based on a low-cost, low-area Spartan 6 device. The converter is based on a tapped delay line model. Several implementation details are discussed with a particular focus on critical blocks such as the input stage and thermometer-to-binary decoding techniques. We implemented a tap filtering technique to improve the differential nonlinearity (DNL) of the single delay line while keeping a good LSB value of 25.57 ps with a single-shot precision (SSP) between $0.69\div 1.46$ LSB. Measured DNL and integral nonlinearity (INL) lie in the range between $-0.90\div 1.23$ and $-0.43\div 2.96$ LSB, respectively. Measured DNL and INL lie in the range between $-0.90\div 1.23$ and $-0.43\div 2.96$ LSB, respectively. We then implemented an interpolating TDC to overcome the limitations of a single delay line in terms of linearity and measurement range. The interpolating TDC uses the sliding scale technique, where the time interval to be measured is asynchronous with respect to the FPGA clock, achieving DNL and INL in the range $-0.072\div 0.070$ and $-0.755\div 0.872$ LSB. SSP is in the $1.096\div 2.815$ range. Moreover, we present a novel comparison between the DNLs obtained with two different methods: statistical code density test and using a finely controlled delay source. Finally, we present the results of a Monte Carlo simulation used to investigate the effects of nonlinear propagation of the signal through the delay line. [ABSTRACT FROM PUBLISHER]

Cross-talk characterization results of high-fill-factor single-photon avalanche diode (SPAD) arrays in CMOS 150-nm technology are reported and discussed. Three different SPAD structures were designed with two different sizes (15.6 and 25.6  μm pitch) and three guard ring widths (0.6, 1.1, and 1.6  μm). Each SPAD was implemented in an array, composed of 25 (5×5) devices, which can be separately activated. Measurement results show that the average cross-talk probability is well below 1% for the shallow-junction SPAD structure with 15.6  μm pitch and 39.9% fill factor, and 1.45% for the structure with 25.6  μm pitch and 60.6% fill factor. An increase of cross-talk probability with the excess bias voltage is observed. [ABSTRACT FROM AUTHOR]

This paper reviews the state of the art of single-photon avalanche diode (SPAD) image sensors for time-resolved imaging. The focus of the paper is on pixel architectures featuring small pixel size (<25 μm) and high fill factor (>20%) as a key enabling technology for the successful implementation of high spatial resolution SPAD-based image sensors. A summary of the main CMOS SPAD implementations, their characteristics and integration challenges, is provided from the perspective of targeting large pixel arrays, where one of the key drivers is the spatial uniformity. The main analog techniques aimed at time-gated photon counting and photon timestamping suitable for compact and low-power pixels are critically discussed. The main features of these solutions are the adoption of analog counting techniques and time-to-analog conversion, in NMOS-only pixels. Reliable quantum-limited single-photon counting, self-referenced analog-to-digital conversion, time gating down to 0.75 ns and timestamping with 368 ps jitter are achieved. [ABSTRACT FROM AUTHOR]

In this paper, a CMOS image sensor based on avalanche photodiodes (APDs) for time-of-flight optical ranging is presented. In-pixel phase-sensitive detection was obtained thanks to the modulation of APD avalanche gain. A pixel based on this principle with 30- \mu \textm pixel pitch and 25.7% fill factor was designed, and a $64 \times 64$ APD image sensor was fabricated in a 0.35- \mu \textm standard CMOS process. The maximum demodulation contrast measured on the array exceeds 85% at 25-MHz modulation frequency. High-frequency modulation was demonstrated on single test pixels, where a demodulation contrast as high as 80% was measured at 200-MHz modulation frequency. A 3-D camera working at a frame rate up to 200 frames/s was realized and characterized. [ABSTRACT FROM AUTHOR]

In this brief, the design and experimental characterization of a compact analog readout circuit for photon counting is presented. A test chip, including a 20 $\times$ 20 counter array, has been manufactured in a standard 0.35- \mu\m CMOS technology. The circuit delivers an output voltage proportional to the input pulse count, with a programmable voltage step. The counting resolution can be set to 7 or 8 bits with a readout noise of 0.15 and 0.3 electrons, respectively, and an output nonuniformity of 4% across the array, which brings a factor 3 improvement with respect to previous analog designs. A worst case integral nonlinearity of \pm$0.6 and \pm$1 LSB and a differential nonlinearity of \pm$0.3 and \pm) is a factor 10 smaller than a digital counter of the same resolution. Due to the compactness and the lower counter power consumption with regard to the former designs, the proposed circuit can be exploited for signal processing in high-spatial resolution single-photon-avalanche-diode-based image sensors. [ABSTRACT FROM PUBLISHER]

This paper presents a 32\,\times\,32 pixel image sensor for time-gated fluorescence lifetime detection based on single-photon avalanche diodes. The sensor, fabricated in a high-voltage 0.35-\mum CMOS technology, uses an analog counting approach to minimize the area occupation of pixel electronics while maintaining a nanosecond timing resolution and shot-noise-limited operation. The all nMOS pixel is formed by 12 transistors and features 25-\mum pitch and 20.8% fill factor. The chip includes a phase-locked loop circuit for gating window generation, working at a maximum repetition frequency of 40 MHz, while the sensor can be gated at frequency up to 80 MHz using an external delay generator. Optical characterization with a picosecond-pulsed laser showed a minimum gating window width of 1.1 ns. Example images acquired in both continuous and time-gated mode are presented, together with a lifetime image obtained with the sensor mounted on a fluorescence microscope. [ABSTRACT FROM AUTHOR]

This paper presents the design and electro-optical test of a 160\times120-pixels CMOS sensor specifically conceived for Time-Of-Flight 3D imaging. The in-pixel processing allows the implementation of Indirect Time-Of-Flight technique for distance measurement with reset noise removal through Correlated Double Sampling and embedded fixed-pattern noise reduction, whereas a fast readout operation allows the pixels values to be streamed out at a maximum rate of 10 MSample/s. The imager can operate as a fast 2D camera up to 458 fps, as a 3D camera up to 80 fps, or even coupling both operation modes. The chip has been fabricated using a standard 0.18 \mu\m 1P4M 1.8 V CMOS technology with MIM capacitors. The resulting pixel has a pitch of 29.1 \mu\m with a fill-factor of 34% and includes 66 transistors. Distance measurements up to 4.5 m have been performed with pulsed laser light, achieving a best precision of 10 cm at 1 m in real-time at 55 fps and 175 mA current consumption. [ABSTRACT FROM AUTHOR]

We report on the design of a current-assisted photonic demodulator (CAPD) using standard 0.18- \mu\m complementary metal–oxide–semiconductor technology and its electrooptical characterization. The device can perform both light detection and demodulation in the charge domain, owing to a drift field generated in the silicon substrate by a majority carrier flow. Minimum-sized \10 \times \10\ \mu\m^2 CAPDs exhibit a direct-current charge–transfer efficiency larger than 80% (corresponding to demodulation contrast larger than 40% under sine-wave modulation) at the modest power consumption of 10 \mu\W and a 3-dB bandwidth of > 45 MHz. An excellent linearity value with an error lower than 0.11% is obtained in phase measurements. CAPDs with optimized modulation electrode geometries are finally designed, aiming at an improved contrast-versus-power tradeoff. [ABSTRACT FROM PUBLISHER]

This paper presents the design and characterization of a lock-in pixel array based on a buried channel photo-detector aimed at time-of-flight range imaging. The proposed photo-demodulator has been integrated in a 10-\mu\ m pixel pitch with a fill factor of 24%, and is capable of a maximum demodulation frequency of 50 MHz with a contrast of 29.5%. The sensor has been fabricated in a 0.18-\mu\ m CMOS imaging technology and assembled in a range camera system setup. The system provides a stream of three-dimensional images at 5–20 fps on a 3–6 m range, with a linearity error lower than 0.7% and a repeatability of 5–16 cm, while the best achievable precision is 2.7 cm at a 50-MHz modulation frequency. [ABSTRACT FROM AUTHOR]

In this paper, we report on an Avalanche Photodiode (APD) fabricated in a standard 0.35-μm CMOS technology. The main electrooptical characteristics of the device are presented, showing a remarkably tow-noise factor if compared to other CMOS APDs. An estimation of the noise properties of a pixel based on the proposed photodiode with charge-amplifier readout is performed, showing that it could have an improved noise performance with respect to a standard photodiode-based pixel. [ABSTRACT FROM AUTHOR]

We report on n-channel Junction Field Effect Transistors fabricated on high resistivity silicon by means of a specially tailored radiation detector technology. This research activity is being carried out in the framework of a project aiming at the integration of read-out circuits in the same detector substrate. Possible applications are in the field of medical/industrial imaging, space and high energy physics experiments. The pre-existent fabrication process has been modified in several respects to enhance the device noise behavior. In particular, the new process features a high-energy (1 MeV) Boron implantation to obtain a deep p-well which ensures an effective isolation of the transistor from the substrate and a strong modulating effect on the current. Selected results from the experimental characterization of transistors and charge sensitive amplifiers are presented, showing a sizable enhancement in the noise performance with respect to previously available devices. [ABSTRACT FROM AUTHOR]

Fully Depleted Monolithic Active Pixel Sensors (FD-MAPS) represent an appealing alternative to hybrid detectors for radiation imaging applications. We have recently demonstrated the feasibility of FD-MAPS based on a commercial 110 nm CMOS technology, adapted using high-resistivity substrates and backside post-processing. A p/n junction diode, fabricated on the detector backside using low-temperature processing steps after the completion of the front-side Back End of Line (BEOL), is reverse-biased to achieve the full depletion of the substrate and thus fast charge collection by drift. Test diodes including termination structures with different numbers of floating guard rings and different pitches were fabricated together with other Process Control Monitor structures. In this paper, we present the design of the backside diodes, together with results from the electrical characterization of the test devices, aiming to improve understanding of the strengths and limitations of the proposed approach. Characterization results obtained on several wafers demonstrate the effectiveness of the termination rings in increasing the breakdown voltage of the backside diodes and in coping with the variability of the passivation layer characteristics. A breakdown voltage exceeding 400 V in the worst case was demonstrated in devices with 30 guard rings with 6 μm pitch, thus enabling the full depletion of high-resistivity substrates with a thickness larger than or equal to 300 μm. Additionally, we show the first direct comparison for this technology of measured pixel characteristics with 3D TCAD simulations, proving a good agreement in the extracted operating voltages. [ABSTRACT FROM AUTHOR]

This letter presents the experimental characterization and noise modeling of a CMOS avalanche photodiode with pwell/n-iso active junction fabricated in a 0.15- \mum standard CMOS process. The device exhibits a remarkably low excess noise factor F=6 at a gain M={50} in the blue spectral region, and F={12}$ at M={50} in the near-infrared. Gain and noise characteristics are accurately predicted using Hayat dead-space model applied to a linearly graded junction doping profile. [ABSTRACT FROM AUTHOR]

Transimpedance amplifiers (TIA) are widely used for front-end signal conditioning in many optical distance measuring applications in which high accuracy is often required. Small effects due to the real characteristics of the components and the parasitic elements in the circuit board may cause the error to rise to unacceptable levels. In this work we study these effects on the TIA delay time error and deduce analytic expressions, taking into account the trade-off between the uncertainties caused by the delay time instability and by the signal-to-noise ratio. A specific continuous-wave phase-shift case study is shown to illustrate the analysis, and further compared with real measurements. General strategies and conclusions, useful for designers of this kind of system, are extracted too. The study and results show that the delay time thermal stability is a key determinant factor in the measured distance accuracy and, without an adequate design, moderate temperature variations of the TIA can cause extremely high measurement errors. [ABSTRACT FROM AUTHOR]

Photodetectors based on transition metal dichalcogenides (TMDs) have been widely reported in the literature and molybdenum disulfide (MoS2) has been the most extensively explored for photodetection applications. The properties of MoS2, such as direct band gap transition in low dimensional structures, strong light–matter interaction and good carrier mobility, combined with the possibility of fabricating thin MoS2 films, have attracted interest for this material in the field of optoelectronics. In this work, MoS2-based photodetectors are reviewed in terms of their main performance metrics, namely responsivity, detectivity, response time and dark current. Although neat MoS2-based detectors already show remarkable characteristics in the visible spectral range, MoS2 can be advantageously coupled with other materials to further improve the detector performance Nanoparticles (NPs) and quantum dots (QDs) have been exploited in combination with MoS2 to boost the response of the devices in the near ultraviolet (NUV) and infrared (IR) spectral range. Moreover, heterostructures with different materials (e.g., other TMDs, Graphene) can speed up the response of the photodetectors through the creation of built-in electric fields and the faster transport of charge carriers. Finally, in order to enhance the stability of the devices, perovskites have been exploited both as passivation layers and as electron reservoirs. [ABSTRACT FROM AUTHOR]

A burst image sensor named Hanabi, meaning fireworks in Japanese, includes a branching CCD and multiple CMOS readout circuits. The sensor is backside-illuminated with a light/charge guide pipe to minimize the temporal resolution by suppressing the horizontal motion of signal carriers. On the front side, the pixel has a guide gate at the center, branching to six first-branching gates, each bifurcating to second-branching gates, and finally connected to 12 ( = 6 × 2 ) floating diffusions. The signals are either read out after an image capture operation to replay 12 to 48 consecutive images, or continuously transferred to a memory chip stacked on the front side of the sensor chip and converted to digital signals. A CCD burst image sensor enables a noiseless signal transfer from a photodiode to the in-situ storage even at very high frame rates. However, the pixel count conflicts with the frame count due to the large pixel size for the relatively large in-pixel CCD memory elements. A CMOS burst image sensor can use small trench-type capacitors for memory elements, instead of CCD channels. However, the transfer noise from a floating diffusion to the memory element increases in proportion to the square root of the frame rate. The Hanabi chip overcomes the compromise between these pros and cons. [ABSTRACT FROM AUTHOR]

The paper presents the simulation studies of 10 μ m pitch microstrips on a fully depleted monolithic active CMOS technology and describes their potential to provide a new and cost-effective solution for particle tracking and timing applications. The Fully Depleted Monolithic Active Microstrip Sensors (FD-MAMS) described in this work, which are developed within the framework of the ARCADIA project, are compliant with commercial CMOS fabrication processes. A set of Technology Computer-Aided Design (TCAD) parametric simulations was performed in the perspective of an upcoming engineering production run with the aim of designing FD-MAMS, studying their electrical characteristics, and optimizing the sensor layout for enhanced performance in terms of low capacitance, fast charge collection, and low-power operation. A fine pitch of 10 μ m was chosen to provide high spatial resolution. This small pitch still allows readout electronics to be monolithically integrated in the inter-strip regions, enabling the segmentation of long strips and the implementation of distributed readout architectures. The effects of surface radiation damage expected for total ionizing doses of the order of 10 to 10 5 krad were also modeled in the simulations. The results of the simulations exhibit promising performance in terms of timing and low power consumption and motivate R&D efforts to further develop FD-MAMS; the results will be experimentally verified through measurements on the test structures that will be available from mid-2021. [ABSTRACT FROM AUTHOR]

Electrical conductivity of porous silicon fabricated from heavily doped p-type silicon is very sensitive to NO2, even at concentrations below 100 ppb. However, sensitivity depends strongly on the porous microstructure. The structural difference between sensitive and insensitive samples is independently confirmed by microscopy images and by light scattering behavior. A way to change the structure is by modifying the composition of the electrochemical solution. We have found that best results are achieved using ethanoic solutions with HF concentration levels between 12% and 13%. [ABSTRACT FROM AUTHOR]

The electrical conductance of porous silicon fabricated with heavily doped p-type silicon is very sensitive to NO2. We show that the sign of the injection variations depends on the porous layer thickness. If the thickness is sufficiently low—of the order of few μm—the injection decreases instead of increasing. We discuss the effect in terms of an already proposed twofold action of NO2, according to which the free carrier density increases, and simultaneously the energy bands are bent at the porous silicon surface. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]