Search

As devices scale closer to the atomic size, a complete understanding of the physical mechanisms involving defects in high-κ dielectrics is essential to improve the performance of electron devices and to mitigate key reliability phenomena, such as Random Telegraph Noise (RTN). In fact, crucial aspects of defects in HfO2 are still under investigation (e.g., the presence of metastable states and their properties), but it is well known that oxygen vacancies (V+s) and oxygen ions (O0s) are the most abundant defects in HfO2. In this work, we use simulations to gain insights into the RTN that emerges when a constant voltage is applied across a TiN/(4 nm)HfO2/TiN stack. Signals exhibit different RTN properties over bias and, thus, appear to originate from different traps. Yet, we demonstrate that they can be instead promoted by the same O0s which change their capture (τc) and emission (τe) time constants with the applied bias, which, in turn, changes the extent of their electrostatic interactions with the traps that assist charge transport (V+s). For a certain bias, RTN is given by the modulation of the trap-assisted current at V+s induced by trapping/detrapping events at O0s, which are, in turn, influenced by the bias itself and by trapped charge at nearby O0s. In this work, we demonstrate that accounting for the effect of trapped charge is essential to provide accurate estimation of the RTN parameters, which allow us to retrieve information about traps and to explain key mechanisms behind complex RTN signals. [ABSTRACT FROM AUTHOR]

The recent discovery of ferroelectricity in HfO2 has revived the interest into non-volatile memories based on ferroelectric transistors (FeFETs). The key advantages of these FeFETs include the low power consumption and the compatibility with the existing CMOS process. On the other hand, issues related mainly to endurance still represent a challenge to the development of the technology. In this Letter, we propose to exploit an analytical expression for the Memory Window (MW) as a simple yet effective characterization tool to evaluate the endurance of FeFETs. The MW is defined as the difference between threshold voltages occurring due to polarization switching. The analytical formulation of the MW allows one to quickly estimate the generated trap concentration as a function of number of writing cycles (or time) without recurring to numerical simulations. With the aid of the analytical model, we find that for typical program/erase pulse amplitudes and duration, endurance has a weak dependence on writing conditions. The characterization technique based on the MW would allow the systematic comparison of the performance and endurance of next-generation FeFETs. [ABSTRACT FROM AUTHOR]

In this article, we present coupled experimental/simulated results about the influence of interface and border traps on the electrical characteristics and split-CV mobility extraction in InGaAs MOSFETs. These results show that border traps limit the maximum drain current under on-state conditions, induce a hysteresis in the quasi-static transfer characteristics, as well as affect CV measurements, inducing an increase in the accumulation capacitance even at high frequencies where trap effects are commonly assumed to be negligible. Hysteresis in the transfer characteristics can be used as a sensitive monitor of border traps, as suggested by a sensitivity analysis where either the energetic or the spatial distribution of border traps are varied. Finally, we show that mobility extraction by means of the split-CV method is affected by appreciable errors related to the spurious contributions of interface and border traps to the total gate charge, ultimately resulting in significant channel mobility underestimation. In very narrow channel devices, channel electron spilling over the InP buffer layer can also contribute to mobility measurement inaccuracy. [ABSTRACT FROM AUTHOR]

In this paper, we propose new guidelines for the analysis of random telegraph noise (RTN) in electronic devices. Starting from an in-depth understanding of RTN signal characteristics, we will identify the correct measurement conditions to enable RTN analysis as a characterization tool for electronic devices. The estimate of RTN statistical parameters may indeed strongly depend on the choice of measurement conditions. We will carefully consider both the measurement limits and the extraction process constraints to devise a strategy to identify RTN signals measured in conditions allowing a meaningful estimation of their parameters. The proposed strategy will be tested on a variety of different RTN signals and operating conditions. [ABSTRACT FROM PUBLISHER]

In this work, we present a thorough statistical characterization of Random Telegraph Noise (RTN) in HfO 2 -based Resistive Random Access Memory (RRAM) cells in Low Resistive State (LRS). Devices are tested under a variety of operational conditions. A Factorial Hidden Markov Model (FHMM) analysis is exploited to extrapolate the properties of the traps causing multi-level RTN in LRS. The trapping and de-trapping of charge carriers into/out of defects located in the proximity of the conductive filament results in a shielding effect on a portion of the conductive filament, leading to the observed RTN current fluctuations. It is found that both oxygen vacancies and oxygen ions defects may be responsible for the observed RTN. The variations of the current observed at subsequent set/reset cycles are instead attributed to the stochastic variations in the filament due to oxidation/reduction processes during reset and set operations, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a statistical characterization of random telegraph noise (RTN) in hafnium-oxide-based resistive random access memories (RRAMs) in high resistive state (HRS). Complex RTN signals are analyzed exploiting a Factorial Hidden Markov Model (FHMM) approach, which allows to derive the statistical properties of the RTN signals, directly related to the physical properties of the traps responsible for the multi-level RTN measured in these devices. Noise characteristics in different reset conditions are explored through consecutive switching cycles. Noise spectral analysis is also performed to fully support the investigation. An RRAM compact model is also exploited to estimate the physical properties of the conductive filament and of the dielectric barrier from simple I – V data. These tools are combined together to prove the existence of a direct statistical relation between the reset conditions, the volume of the dielectric barrier created during the reset operation and the average number of active traps contributing to the RTN. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we analyze Random Telegraph Signal (RTS) noise and Power Spectral Density (PSD) in hafnium-based RRAMs. RTS measured in HRS exhibits fast and slow multilevel switching events. RTS characteristics are examined through novel color-coded time-lag plots and Hidden Markov Model (HMM) time-series analyses. Results are validated by comparing simulated and experimental PSD. Noise is examined at different reset conditions to provide an insight into the conduction mechanisms in HRS. Higher reset voltages are found to result in greater RTS complexity due to a larger number of active traps as confirmed by PSD. [Copyright &y& Elsevier]

Abstract: The performance of mesophilic anaerobic digesters of four large Italian wastewater treatment plants without primary sedimentation were studied. Only the waste activated sludge is stabilised by means of the mesophilic (35–37°C) anaerobic digestion process. The anaerobic digesters generally worked with a hydraulic retention time in a range of 20–40 days and an organic loading rate of some 1kgVS/day. The solids content of the sludge fed to the digesters was in the range 2.6–3.9% and the gas produced per kilogram of volatile solids added was in the range 0.07–0.18m3/kgVSfed. The specific gas production per kilogram of volatile solids destroyed was in the range 0.5–0.9m3/kgVSdestroyed and the reduction of the volatile solids concentration was in the range 13–27% (average 18%). These figures are particularly significant when designing anaerobic digesters for the treatment of waste activated sludge as single substrate. Moreover, it was observed that the higher the applied solid retention time in the activated sludge process for wastewater treatment, the lower the gas production. In particular, the specific gas production decreased from 0.18 to 0.07m3/kgVSfed when increasing the solid retention time in the wastewater treatment line from 8 to 35 days. Finally, a mathematical model for the prediction of biogas production on the solid retention time applied in the wastewater treatment process was developed. [Copyright &y& Elsevier]

In this paper, through the use of a recently proposed statistical model of stress-induced leakage current, we will investigate the reliability of actual Flash memory technologies and predict future trends. We investigate either program disturbs (namely gate and drain disturbs) and data retention of state-of-the-art Flash memory cells and use this model to correlate the induced threshold voltage shift to the typical outputs coming from oxide characterization, that are density, cross section, and energy level of defects. Physical mechanisms inducing the largest threshold voltage (VT) degradation will be identified and explained. Furthermore, we predict the effects of tunnel oxide scaling on flash memory data retention, giving a rule of thumb to scale the tunnel oxide while maintaining the same retention requirements. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to investigate the physical mechanism of NROM memory erase. Three conduction mechanisms potentially responsible of NROM erase will be analyzed (tunneling and emission of electrons through both bottom and top oxide, tunneling and injection of holes over the bottom oxide barrier) by means of standard two-dimensional simulations and ad-hoc models reproducing hole and electron transport mechanisms across the oxide not included in standard device simulators. Hot-hole injection will be identified as the actual conduction mechanism of NROM erase, and two compact models capable to describe the main characteristics of NROM erase current will be developed. [ABSTRACT FROM AUTHOR]

E²PROM memory devices are widely used in embedded applications. For an efficient design flow, a correct modeling of these memory cells in every operation condition becomes more and more important, especially due to power consumption limitations. Although E²PROM cells are being used for a long time, very few compact models have been developed. Here, we present a complete compact model based on an original procedure to calculate the floating gate potential in dc conditions, without the need of any capacitive coupling coefficient. This model is designed as a modular structure, so to simplify program/erase and reliability simulations. Program/erase and leakage currents are included by means of simple voltage-controlled current sources implementing their analytical expression. It can be used to simulate memory cells both during read operation (dc conditions) and during program and erase (transient conditions) giving always very accurate results. We will show also that, provided good descriptions of degradation mechanisms, the same model can be used also for reliability simulations, predicting charge loss due to tunnel oxide degradation. [ABSTRACT FROM AUTHOR]

NROMTM––is a new technology for non-volatile memories (NVMs); it offers three major improvements relative to the Floating Gate technology: one technology for all NVM products (Flash, EEPROM, ROM and Embedded), higher density (2.5F2/bit in Flash, where F is the feature size of the process), and simpler process with reduced number of masks without any “exotic” materials. The NROMTM cell is based on localized charge trapping above the junction edge, storing two physically separated bits per cell. Performance of new NVM NROMTM based products show endurance up to 100 K with retention of 10 years at 150 °C. [Copyright &y& Elsevier]

Presents a compact SPICE model of floating gate nonvolatile memory cells capable to reproduce effectively its complete direct current electrical behavior in every bias conditions. Elements of the floating gate cell model developed in a SPICE-like circuit simulator; Advantages of the SPICE model; Ways to simulate the behavior of a memory cell.

Presents a study which proposed a floating gate (FG) memory cell compact model for coupling coefficient approach to calculate the FG voltage. Brief summary of the FG memory cell compact model; Overview of the W/L dependence of capacitive coupling coefficients; Analysis and discussion of extraction methods of capacitive coupling ratios; Conclusions.

Features a study which tackled the difficult task to extract MOS parameters by a model of the gate capacitance that takes into account both poly-silicon depletion and charge quantization and includes temperature effects. High-performance of MOS field-effect transistors for advanced integrated circuits; Description of the model; Results and experimental C-V fitting procedure; Calculation methods; Conclusions.

We present in this work an analysis of transiently triggered latch-up in test-structures fabricated using a twin-tub process implemented on two different substrates: a p-type and a p/p+ epitaxial one. Steady- state electrical characterization confirmed the well-known increased latch-up resistance of epitaxial structures with respect to standard ones. In this paper it is shown that, depending on the chosen electrical configuration, when latch-up is transiently triggered, epitaxial structures may have dynamic triggering currents lower than twin-tub ones. The influence of some layout variables on turn-on threshold voltage has been investigated for all samples. [ABSTRACT FROM AUTHOR]

Presents results of several accelerated tests performed on self-aligned, etched-polysilicon, npn bipolar transistors with silicon dioxide emitter spacers and propose a technique for characterization of the electric field. How the bipolar complementary metal oxide semiconductors (CMOS) process sequence is derived from the pMOS transistor; Difference between avalanche and tunneling stress; Oxide charge estimation.

Presents a detailed experimental and theoretical investigation of hot electron effects occurring in Heterojunction Bipolar Transistors (HBT's) operating at low current densities. Impact of ionization and light emission on electrons heated by the strong electric field at the base-collector junction; Development of a weighted Monte Carlo procedure to study such effects.

Tannery sludge, a challenging waste, was utilized as a substrate for the production of Short-Chain Fatty Acids (SCFAs) through a series of six thermophilic Continuous Stirred-Tank Reactor runs. The sludge was subjected to a mild thermal pre-treatment and incorporated zeolites (chabazite in run II, and clinoptilolite in run III) in the acidification process. Results highlighted zeolites' impact on chromium concentration and the SCFAs/COD SOL ratio. Ammonia release remained consistent at around 47 % and 51 % for run I and II, respectively, but surpassed 60% in run III, suggesting limited zeolite effectiveness in NH 4 absorption. Chromium release in the liquid fraction, due to thermal pretreatment, reached 335 mg/L. While in tests without zeolite, complete removal proved challenging, in zeolite-amended runs, complete removal was achieved, showcasing the materials' heavy metal absorption capacity. SCFA concentrations reached 20260 mgCOD/L, with acidification efficiency varying; runs I and III had ratios around 0.70 COD/COD, while run II showed substantial improvement (0.92) with chabazite. Anaerobic fermentation-digestion mass balance indicated a 41% reduction in landfill sludge mass, reducing its environmental footprint while yielding valuable byproducts like biogas and SCFAs. These findings underscore zeolites' potential in heavy metal absorption and acidification process enhancement, paving the way for applications with tannery sludge. • Up to 20260 mgCOD/L SCFAs with thermally pretreated tannery sludge with HRT 8d. • Chabazite improved sCOD removal by around 20% compared to the blank. • Chabazite with HRT8d allowed for 92% of the sCOD to be converted into SCFAs. • Only runs with Zeolites had a complete removal of Cr from the fermentation broth. [ABSTRACT FROM AUTHOR]

[Display omitted] • Combined thermal-alkaline hydrolysis favored the food waste acidification into OAs; • Mesophilic environment increased the acidification yield up to 0.87 g COD/g VS; • Caproic acid above 30% COD/COD was reached in mesophilic T under the highest OLR; • Multivariate data analysis showed stability in product's quality under mesophilic T; • An economic income of 4,826,051 €/y is achievable in the food waste value chain. Food waste (FW) was subjected to thermal-alkaline hydrolysis before to be used as source for organic acids (OAs) production under different temperatures and hydraulic regime in long-term acidification process. Mesophilic environment led to the highest acidification yield (0.87 g COD OAs /g VS) with chain-elongation process to caproic acid production (>9.0 g COD cap /L) occurring at lower HRT (2 days). The product's quality, in terms of OAs production and composition, was evaluated through a multivariate approach, which indicated that the mesophilic condition was also appropriate to steadily maintain the requested product's features. The specific gas production (SGP) from the solid-rich acidified residue was 0.47 Nm3/kg VS and, in a full-scale scenario of 150,000 kg FW/d, it can be potentially converted into 24.9 MWh/d as electrical energy. Also, according to the acidification performances, an overall OAs production of 7.2 ton/y has been estimated, generating a yearly economic outcome higher than 4,800,000 €. [ABSTRACT FROM AUTHOR]

Variability is one of the major roadblocks for III-V semiconductors in nanoscale devices, according to the recent International Roadmap for Devices and Systems (IRDS). A particular concern is the detrimental effect of variability of threshold voltage due to channel compositional variations. In this paper, we investigate the impact of this variability source and the effects of scaling on the performance of Dual-Gate-Ultra-Thin-Body (DG-UTB) In 0.53 Ga 0.47 As MOSFETs. We model mole fraction variations in terms of the Indium content by taking into account the spatial inhomogeneity of the channel and the corresponding bandgap variations, analyzing the effects on threshold voltage variability. We thus define a variability source, i.e., Band Gap Fluctuation (BGF), and we compare the associated variability with the ones from other important sources, namely, Random Dopant Fluctuation (RDF), Work Function Fluctuation (WFF), Body- and Gate-Line Edge Roughness (B-LER and G-LER). We then define three corner cases for mole fraction variations to determine worst-case variability. Finally, the impact of scaling on variability is assessed by comparing results for two technology nodes on the linear and saturation threshold voltage, V T,lin , V T,sat , on-current, I ON , leakage current, I OFF , and linear and saturation sub-threshold slope, SS. We find that although scaling has no impact on BGF-induced V T variability, it increases the total V T,lin variability as well as that for I ON and I OFF. [ABSTRACT FROM AUTHOR]

• Acidogenic fermentation process was optimized for urban bio-waste valorisation. • Thermal pre-treatment favoured the urban bio-waste organic matter solubilisation. • Mesophilic alkaline fermentation enhanced VFA production yields. • Higher HRTs and lower OLRs gave the best performance in a CSTR with 39 g COD VFA /L. • Alkaline urban bio-waste fermentation increased the HV precursors concentrations. The problem of waste disposal has recently focused on practices for waste recycling and bio-resources valorization. Organic waste produced in urban context together with biological sludge produced in wastewater treatment plants (WWTPs) can be used as renewable feedstock for the production of building blocks of different products, from biopolymers to methyl esters. This paper deals with the optimization of the fermentation process in order to transform urban organic waste (a mixture of pre-treated food waste and biological sludge) into added-value volatile fatty acid (VFA) rich stream, useful for biological processes within a biorefinery technology chain. Different temperatures, pH, hydraulic retention times (HRTs) and organic loading rates (OLRs) were tested both in batch and continuous trials. Batch tests showed the best working conditions at 37 °C and pH 9, using the bio-waste feedstock thermally pre-treated (76 h at 72 °C). These conditions were applied in continuous process, where higher HRT (6.0 d) and lower OLR [7.7 kg VS/(m3 d)] gave the best performances in terms of process yield and maximum VFA level achieved: 0.77 COD VFA /VS (0) and 39 g COD VFA /L. An optimized fermentation process is crucial in a biorefinery perspective since it has to give a final stream of constant composition or tailored products suitable for further applications. [ABSTRACT FROM AUTHOR]

Reducing power consumption in nowadays computer technologies represents an increasingly difficult challenge. Conventional computing architectures suffer from the so-called von Neumann bottleneck (VNB), which consists in the continuous need to exchange data and instructions between the memory and the processing unit, leading to significant and apparently unavoidable power consumption. Even the hardware typically employed to run Artificial Intelligence (AI) algorithms, such as Deep Neural Networks (DNN), suffers from this limitation. A change of paradigm is so needed to comply with the ever-increasing demand for ultra-low power, autonomous, and intelligent systems. From this perspective, emerging memristive non-volatile memories are considered a good candidate to lead this technological transition toward the next-generation hardware platforms, enabling the possibility to store and process information in the same place, therefore bypassing the VNB. To evaluate the state of current public-available devices, in this work commercial-grade packaged Self Directed Channel memristors are thoroughly studied to evaluate their performance in the framework of in-memory computing. Specifically, the operating conditions allowing both analog update of the synaptic weight and stable binary switching are identified, along with the associated issues. To this purpose, a dedicated yet prototypical system based on an FPGA control platform is designed and realized. Then, it is exploited to fully characterize the performance in terms of power consumption of an innovative Smart IMPLY (SIMPLY) Logic-in-Memory (LiM) computing framework that allows reliable in-memory computation of classical Boolean operations. The projection of these results to the nanoseconds regime leads to an estimation of the real potential of this computing paradigm. Although not investigated in this work, the presented platform can also be exploited to test memristor-based SNN and Binarized DNNs (i.e., BNN), that can be combined with LiM to provide the heterogeneous flexible architecture envisioned as the long-term goal for ubiquitous and pervasive AI. [Display omitted] • Smart Imply (SIMPLY) facilitates memristor-based digital Logic in Memory (LiM). • SIMPLY is possible even with commercial-available memristors. • FPGA-based platform is developed to evaluate SIMPLY operation's energy consumption. • Results show great advantages with respect to CMOS counterpart and other reports. [ABSTRACT FROM AUTHOR]

Abstract: The extremely low thermal effusivity of the silica aerogel is exploited to develop a high efficiency thermoacoustic (TA) loudspeaker with solid substrate. The deposition of the electrically conductive, low heat capacity active film on the silica aerogel surface is achieved with both the spray coating of silver nanowires and the sputter coating of gold films. The uniform spray coating of the hydrophobic silica aerogel is enabled by a low pressure plasma treatment, which however impairs its robustness. The spray‐coated samples prove to be fragile when subjected to elevated temperatures and thus not suitable for TA applications. Sputter coating, not requiring any treatment of the aerogel surface, allows the fabrication of working TA loudspeaker samples with a 100 nm gold active film. The electroacoustic response of the gold‐sputtered silica aerogel TA loudspeaker is characterized at different input power levels. The experimental results are compared with those present in literature, showing an improved efficiency with respect to the other TA loudspeakers with solid substrate. [ABSTRACT FROM AUTHOR]

This study compared the performances of single and two-stage anaerobic digestion processes of food waste. The processes were monitored by taking into account both the steady state process performances and the transient conditions. In addition to a conventional univariate analysis, a multivariate analysis to increase the validity of the results of the comparison study was also performed. The transient states caused peaks due to a high organic loading rate, simulating possible overloading events and the recovery capacity of both processes (resilience). The specific gas production of the methanogenic reactor of the two-stage process was higher (0.88 m 3 biogas /kg VS ) than for the single-stage process (0.75 m 3 biogas /kg VS ). This finding was related to the increase in the removal efficiency (of 17%). Considering the pilot-scale results, a comparison of mass and energy balance, and costs (assuming the upgrading of the biogas produced) was also discussed. [ABSTRACT FROM AUTHOR]

The majority of car accidents worldwide are caused by drowsy drivers. Therefore, it is important to be able to detect when a driver is starting to feel drowsy in order to warn them before a serious accident occurs. Sometimes, drivers are not aware of their own drowsiness, but changes in their body signals can indicate that they are getting tired. Previous studies have used large and intrusive sensor systems that can be worn by the driver or placed in the vehicle to collect information about the driver's physical status from a variety of signals that are either physiological or vehicle-related. This study focuses on the use of a single wrist device that is comfortable for the driver to wear and appropriate signal processing to detect drowsiness by analyzing only the physiological skin conductance (SC) signal. To determine whether the driver is drowsy, the study tests three ensemble algorithms and finds that the Boosting algorithm is the most effective in detecting drowsiness with an accuracy of 89.4%. The results of this study show that it is possible to identify when a driver is drowsy using only signals from the skin on the wrist, and this encourages further research to develop a real-time warning system for early detection of drowsiness. [ABSTRACT FROM AUTHOR]

The aim of this study was to verify the efficiency of a separate hydrolysis step by testing different working temperatures (37–55 °C) and hydraulic retention times (two, four and six days) and by evaluating readily biodegradable carbon production. The fermentation products included primarily acetic, propionic and butyric acids. These acids can be easily converted into biogas or can be recovered in a biorefinery approach, for example, to produce polyhydroxyalkanoates. The optimal condition was found by applying an organic loading rate of 17.9 gTVS m −3 with a four-day retention time at 37 °C for an acidification yield of 183.2 gCOD VFA kgVS fed −1 . [ABSTRACT FROM AUTHOR]

The study reported in this paper considered the results of pilot-scale experiments on single and 2-phase anaerobic digestion of waste activated sludge at high rate. Both single and 2-phase digesters were conducted at the same conditions of organic loading and retention time. The 2-phase anaerobic system showed clear increases in terms of organic matter removal and biogas production compared to the single stage system. Particularly, the volatile solids removal rose from 34% in the single stage system to 38% in the 2-phase system. Hence, the global specific biogas production increased 32%, moving from 0.21 to 0.31 m 3 /kgTVS·d respectively for the single and 2-phase systems. The 2-phase system produced 15% more energy than the single stage system. Furthermore, the heat produced in a CHP unit satisfied all heat requirements insuring more than the complete energetic sustainability of the process. Finally, both single and 2-phase digestates showed to meet requirements established for sludge reuse in agriculture regarding pathogens, metals and organic contaminants. A preliminary economic analysis showed the possibility to pay back the investment for the implementation of a second anaerobic reactor in 3 years because of both the increased biogas production and reduced quantity of excess sludge to be disposed of. [ABSTRACT FROM AUTHOR]

This paper presents a physics-based compact model for the program window in HfOx resistive random access memory devices, defined as the ratio of the resistances in high resistance state (HRS) and low resistance state (LRS). This model allows extracting the characteristics of the conductive filament (CF) in HRS. For a given forming current compliance limit, the program window is shown to be correlated to the thickness of the reoxidized portion of the CF in HRS, which can be modulated by the reset voltage amplitude. On the other hand, the statistical distribution of the memory window depends exponentially on the barrier thickness variations that points to the critical role of reset conditions for the performance optimization of RRAM devices. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents the results of a pilot- and full-scale experimental campaign on the anaerobic co-digestion of waste activated sludge and biowaste both in mesophilic and thermophilic conditions. The study demonstrated the possibility to increase the specific biogas production from 0.34 to 0.49 m3/kgTVS and the gas production rate from 0.53 to 0.78 m3per m3 of reactor per day changing the reactor temperature from the mesophilic (37 °C) to the thermophilic (55 °C) range. The experimental work was carried out at pilot-scale, and the results match the full-scale behaviour. Ammonia nitrogen recycled from the anaerobic digestion section to the wastewater treatment plant accounted for about 4% of the total nitrogen loading. Digestate characteristics in terms of biological stability and heavy metals content suggested the opportunity of a short time post-aerobic stabilisation, leading to a high quality compost product. [Copyright &y& Elsevier]

Abstract: We present an analytical model of TANOS program/erase transients that can be used to implement a compact SPICE-like model of these memory devices. Simulation results obtained from a physics-based TANOS model are used to derive simple analytical formulas relating the program/erase currents and the centroid of the trapped charge distribution to operating conditions and stack composition. The model allows reproducing with a good agreement the experimental program/erase transients, thus providing a valuable tool for IC designers to optimize TANOS memory circuits, especially in the framework of multi-level applications. [Copyright &y& Elsevier]

Abstract: The paper presents the results of a study focused on the occurrence and removal of dioxins and furans (PCDD/F) and poly-chlorinated biphenyls (PCB) in both conventional and membrane wastewater treatment processes. It was found that the conventionally activated sludge process could perform a good removal of PCDDs/Fs and PCBs, but the relatively low solid retention time applied and the presence of suspended solids in the effluent limited the removal capability of the system. On the other hand, the membrane bioreactor was capable of perfectly removing PCDDs/Fs and PCBs giving an effluent characterised by concentrations under the limit of detection for most of the tested compounds. This efficiency was the result of both the solids removal from the effluent (permeate) and the application of prolonged solid retention times which enabled the bioconversion of those compounds as demonstrated by the mass balances. A mathematical model was developed to predict the final fate of a given molecule according to the operational conditions applied in the wastewater treatment process. [ABSTRACT FROM AUTHOR]

The NROM-cell concept has been introduced as a promising technology to replace Flash nonvolatile memory devices also in embedded products, owing to its intrinsic 2-b/cell operation and better endurance. However, the presence of physically separated electron and hole distributions generated by program and erase operations is reported to be one of the main causes of the device's retention degradation. Therefore, a deep knowledge of the features and evolution of the nitride-storage charge is crucial for reliability, cell optimization, future scalability, and multilevel operation. In this scenario, the purpose of this paper is twofold, which is as follows: 1) to introduce a combined simulative experimental method allowing profiling hole distribution in devices erased with different bias conditions and 2) to monitor through this technique the evolution of the nitride charge with cycling, correlating it to the degradation of memory reliability after cycling. [ABSTRACT FROM AUTHOR]

A high-performance optical system to reduce measuring errors and uncertainty in angular encoders is presented. We propose a novel reading optical head, which exploits a lens system to improve the speed of the beam crossing the photodetector and a quadrant photodiode to perform a zero-crossover acquisition of the timing information. [ABSTRACT FROM AUTHOR]

Reports on the achievement of a correct description of programming charge distribution in NROM memory devices. Use of an inverse modeling based methodology using measurements easily performed; Implementation of a simple model of programming charge distribution in two-dimensional TCAD simulations.

In this paper the effect of different SRT on the performances of an ultrafiltration pilot MBR operating with real wastewaters was tested to analyse both the ability of the system to remove nutrients and micropollutants and the possible decrease in waste sludge production. Increasing MLSS from 4 to 9 g/l reduced biomass production by 84% and increasing MLSS from 9 g/l to 17 g/l reduced biomass production by 75%. The progressive sludge mineralization was clear since the VSS decreases from 75% TSS to 52% TSS. The industrial fraction of the influent affected the denitrification in all the three periods. The effluent quality increased only when passing from short SRT to long SRT. Ag, Cd and Sn removal was >99% in all the runs. Cu removal was 72–89%. Hg removal was >90% while Pb had varying behavior due to its inconstant presence in the influent (50–65%). B and Se seemed not to be efficiently retained by the biomass in both experimental conditions (0–28% and 0–31%, respectively). Arsenic was a major concern (33–37%). The next step of the research will focus on the possibility of enhancing As removal by looking at alternative technologies to integrate with the UF process. [Copyright &y& Elsevier]

In this brief, we investigate the bidirectional threshold voltage drift (Δ VT) following negative-bias temperature instability (NBTI) stress in carbon-doped fully recessed AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors (MIS-HEMTs). Several stress conditions were applied at different: 1) gate biases (VGS,STR); 2) stress times (tSTR); and 3) temperatures (T). Both negative and positive Δ VT (thermally activated with different activation energies, EA) were observed depending on the magnitude of VGS,STR. In accordance with the literature, observed Δ VT < 0 V (EA ≅ 0.5 eV) under moderate stress is attributed to the emission of electrons from oxide and interface traps. Instead, Δ VT > 0 V (EA ≅ 0.9 eV) under high stress is attributed to the increased negatively ionized acceptor trap density in the buffer associated with carbon doping. [ABSTRACT FROM AUTHOR]

RON degradation due to stress in GaN-based power devices is a critical issue that limits, among other effects, long-term stable operation. Here, by means of 2-D device simulations, we show that the RON increase and decrease during stress and recovery experiments in carbon-doped AlGaN/GaN power metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) can be explained with a model based on the emission, redistribution, and retrapping of holes within the carbon-doped buffer (“hole redistribution” in short). By comparing simulation results with front- and back-gating OFF-state stress experiments, we provide an explanation for the puzzling observation of both stress and recovery transients being thermally activated with the same activation energy of about 0.9 eV. This finds a straightforward justification in a model in which both RON degradation and recovery processes are limited by hole emission by dominant carbon-related acceptors that are energetically located at about 0.9 eV from the GaN valence band. [ABSTRACT FROM AUTHOR]

• Added-value biopolymer from urban food waste and sewage sludge mixture. • Organic loading rate regulated according to seasonal temperature variation. • The biomass exhibited higher polymer storage response at lower temperature. • The highest polymer productivity at the highest temperature. • PHA biomass content and productivity for the technical-economic process evaluation. The utilisation of urban organic waste as feedstock for polyhydroxyalkanoates (PHA) production is growing since it allows to solve the main concerns about their disposal and simultaneously to recover added-value products. A pilot scale platform has been designed for this purpose. The VFA-rich fermentation liquid coming from the anaerobic treatment of both source-sorted organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS) has been used as substrate for the aerobic process steps: a first sequencing batch reactor (SBR, 100 L) for the selection of a PHA-producing biomass, and a second fed-batch reactor (70 L) for PHA accumulation inside the cells. The SBR was operated at 2.0-4.4 kg COD/(m3 d) as OLR, under dynamic feeding regime (feast-famine) and short hydraulic retention time (HRT; 1 day). The selected biomass was able to accumulate up to 48% g PHA/g VSS. Both steps were performed without temperature (T) control, avoiding additional consumption of energy. In this regard, the applied OLR was tuned based on environmental T and, as a consequence, on biomass kinetic, in order to have a constant selective pressure. The latter was mainly quantified by the PHA storage yield (Y P/S feast 0.34-0.45 COD P /COD S), which has been recognized as the main parameters affecting the global PHA productivity [1.02-1.82 g PHA/(L d)] of the process. [ABSTRACT FROM AUTHOR]

Logic-in-memory (LiM) circuits based on resistive random access memory (RRAM) devices and the material implication logic are promising candidates for the development of low-power computing devices that could fulfill the growing demand of distributed computing systems. However, these circuits are affected by many reliability challenges that arise from device nonidealities (e.g., variability) and the characteristics of the employed circuit architecture. Thus, an accurate investigation of the variability at the array level is needed to evaluate the reliability and performance of such circuit architectures. In this work, we explore the reliability and performance of smart IMPLY (SIMPLY) (i.e., a recently proposed LiM architecture with improved reliability and performance) on two 4-kb RRAM arrays based on different resistive switching oxides integrated in the back end of line (BEOL) of the 0.25-μm BiCMOS process. We analyze the tradeoff between reliability and energy consumption of SIMPLY architecture by exploiting the results of an extensive array-level variability characterization of the two technologies. Finally, we study the worst case performance of a full adder implemented with the SIMPLY architecture and benchmark it on the analogous CMOS implementation. [ABSTRACT FROM AUTHOR]

We investigate the reliability of state-of-the-art SiGe heterojunction bipolar transistors (HBTs) in 55-nm technology under mixed-mode stress. We perform electrical characterization and implement a TCAD model calibrated on the measurement data to describe the increased base current degradation at different collector-base voltages. We introduce a simple and self-consistent simulation methodology that links the observed degradation trend to interface traps generation at the emitter/base spacer oxide ascribed to hot holes generated by impact ionization (II) in the collector/base depletion region. This effectively circumvents the limitations of commercial TCAD tools that do not allow II to be the driving force of the degradation. The approach accounts for self-heating and electric fields distribution allowing to reproduce measurement data including the deviation from the power-law behavior. [ABSTRACT FROM AUTHOR]

Thanks to their superior transport properties, indium gallium arsenide (InGaAs) metal–oxide–semiconductor field-effect transistors (MOSFETs) constitute an alternative to conventional silicon MOSFETs for digital applications at ultrascaled nodes. The successful integration of this technology is challenged mainly by the high defect density in the gate oxide and at the interface with the semiconductor channel, which degrades the electrostatics and could limit the potential benefits over Si. In this work, we: 1) establish a systematic modeling approach to evaluate the performance degradation due to interface traps in terms of electrostatics and transport of InGaAs dual-gate ultrathin body (DG-UTB) FETs and 2) investigate the effects of random interface-trap concentration as another roadblock to the scaling of the technology, due to statistical variability of the threshold voltage. Variability is assessed with a Technology CAD (TCAD) simulator calibrated against multi-subband Monte Carlo (MSMC) simulations. The modeling approach overcomes the TCAD limitations when dealing with ultrathin channels (i.e., below 5 nm) without altering crucial geometrical parameters that would compromise the dependability of the variability analysis. Our results indicate that interface-trap fluctuation becomes comparable with the other variability sources dominating the total variability when shrinking the device dimensions, thus contrasting the trend of reduced variability with scaling. This, in turn, implies that interface and border traps may strongly limit the benefits of InGaAs over Silicon if not effectively reduced by gate process optimization. [ABSTRACT FROM AUTHOR]

Herein, the critical role of carbon doping in the electrical behavior of AlGaN/GaN high electron mobility transistors (HEMTs) on semi‐insulating SiC substrates is assessed by investigating the off‐state three‐terminal breakdown, current collapse, and dynamic on‐resistance recovery at high drain–source voltages. Extensive device simulations of typical GaN HEMT structures are conducted and compared with experimental data from published, state‐of‐the‐art technologies to 1) explain the slope of the breakdown voltage as a function of the gate‐to‐drain spacing lower than GaN critical electric field as a result of the nonuniform electrical field distribution in the gate–drain access region; 2) attribute the drain current collapse to trapping in deep acceptor states in the buffer associated with carbon doping; and 3) interpret the partial dynamic on‐resistance recovery after off‐state stress at high drain–source voltages as a consequence of hole generation and trapping. [ABSTRACT FROM AUTHOR]

Chicken manure was treated in a pilot scale reactor anaerobic membrane bioreactor constituted by a completely mixed reactor combined with an ultrafiltration tube-shaped membrane in a side-stream configuration. The process operated under mesophilic condition and the inhibition of high concentration of ammonia was avoided using an ammonia stripping system. The experimental plan included a preliminary evaluation, where organic loading rates between 1.0 and 7.6 kgVS/m3/day were tested. The organic load higher than 4 kgVS/m3/d caused the accumulation of volatile fatty acids and process instability. Application of the ammonia stripping was also evaluated. The best performances were achieved using a retention time of 21 days, an organic load between 1.4 and 2.0 kgVS/m3/d, and the recirculation of stripped permeate. Reduction of the ammonia permeate content by 90% through stripping and utilization of a mixture of chicken manure/water/permeate in a ratio of 0.22/0.72/0.72 w/w led to a specific biogas production of 0.59 m3biogas/kgVS and methane content of 66–69%. The ammonia thus removed can be recovered by sulphuric acid treatment as ammonium sulphate, which can be used as a fertilizer. The proposed configuration allowed satisfactory biogas production with appropriate methane percentages, recovery of ammonium sulphate, and a high-quality effluent. • Treatment of chicken manure under mesophilic condition in a single-stage mono-digestion configuration is feasible in AnMBR. • Maximum specific gas production (0.59 m3 biogas /kgVS) with 66–69% of methane was achieved recirculating stripped permeate. • The highest performances were reached using a mix of chicken manure/permeate/water in a ratio of 0.22/0.72/0.72 w/w. • Air stripping and sulphuric acid treatment led to 90% ammonium abatement. [ABSTRACT FROM AUTHOR]

We investigate the electron/hole trapping phenomena in alumina blocking oxide and their impact on the program/erase operations and retention of TaN/Al2O3/Si3N4/SiO2/Si (TANOS) memory devices. For this purpose, we perform simulations using a physical model that reproduces the charge injection/trapping in TANOS devices, which is extended in order to account for the charge trapping phenomena in the blocking layer. We derive the electrical characteristics of both electron and hole traps in Al2O3 by reproducing the measured program, erase, and retention transients. Our results show that the amount of electron charge trapped in the alumina during a program operation strongly depends on the stack composition and program voltages and can account for up to 25% of the total threshold voltage shift, whereas hole trapping during erase is negligible. Finally, we investigate the degradation of retention caused by the electron trapping in the alumina blocking layer, which is shown to result in an accelerated charge loss. [ABSTRACT FROM AUTHOR]

Exploiting tannery sludge as potential source of short-chain fatty acids (SCFAs) and biogas offers a promising solution for a new management of this waste, which is currently landfilled due to chromium presence. This study assessed the optimal hydrogen peroxide (H 2 O 2) dosage, temperature (T) and hydraulic retention time (HRT) through hydrolysis and acidification tests to maximize SCFAs production and to recover biogas from the solid-rich fermentation residue. A dosage of 0.4 g H 2 O 2 /g TS and mesophilic T (40 °C) were the most suitable conditions to promote sludge biodegradability and SCFAs production in batch tests. Afterwards, among the two investigated HRT (4 and 8 days) in the semi-continuous processes, longer HRT increased SCFAs concentration and acidification yield up to 16.0 g COD SCFAs /L and 0.32 g COD SCFA /g VS 0 , respectively. Chromium was initially released in the liquid phase, but completely removed in less than 5 HRTs, allowing the utilization of fermentation liquid without environmental-safety issues. Finally, the solid-rich residue showed its potential as biogas source, having a specific gas production (SGP) of 0.48 m3/kg VS. According to the mass balance assessment, more than 50% of sludge can be saved from landfill, with potential economic benefit close to 2,700,000 €/y compared to the current management practice. [Display omitted] • An increase of 11–13% of tannery sludge biodegradability (k h) with 0.4 g H 2 O 2 /g TS. • Higher HRT (8 d) boosted the mesophilic SCFAs yield compared to shorter one (4 d). • Acetic acid accounted for more than 60% of the total SCFAs (COD basis). • Fermentation broth had no environmental issues due to the Cr precipitation. • The mass balance assessment showed a reduction of > 50% of this sludge to landfill. [ABSTRACT FROM AUTHOR]

The present study describes the microbial production of polyhydroxyalkanoates (PHA) from thermally pre-treated sewage sludge at pilot scale level, investigating for the first time the effect of the organic loading rate (OLR) under oxygen limitation on biomass storage properties and kinetics. Polymer characteristics have been also evaluated. The selection/enrichment of PHA-storing biomass was successfully achieved in a Sequencing Batch Reactor (SBR) under short hydraulic retention time (HRT; 2 days). Low OLR (2.05 g COD/L d) was ideal for the selection of an efficient PHA-producing consortium cultivated under limited oxygen availability. In the fed-batch accumulation conducted under high DO regime, such biomass was characterized by 51% of PHA content on cell dry weight, with a related storage yield (Y P/S batch) of 0.61 COD PHA /COD S. On the contrary, medium OLR (4.56 g COD/L d) was not technically feasible to sustain the required consortium's selection under low DO regime. The PHA produced by biomass cultivated under low DO regime was characterized higher thermal stability and crystalline domain compared to PHA traditionally produced under high DO regime. The mass balance assessment highlighted a global yield of 51 g PHA/kg VS (volatile solids of thickened sludge), which was 9% lower than yield obtained under high DO regime, in the face of a realistic reduction of the energy cost of the process. [Display omitted] • Low DO regime sustained the PHA-storing biomass selection in SBR at low OLR. • High OLR was not technically suitable to select PHA-storing biomass at low DO. • Butyrate and valerate were preferentially consumed in the fed-batch accumulations. • The extracted PHA had high thermal stability and crystalline domain. • An overall PHA yield of 51 g PHA/g VS from sewage sludge was quantified. [ABSTRACT FROM AUTHOR]

Examines the hot-electron electroluminescence in aluminum gallium arsenide/gallium arsenide heterojunction bipolar transistors. Recombination of cold electrons and holes; Dependence of electroluminescence on reverse collector-base voltage; Generation of emitter current by impact ionization.

Abstract A combined acidic fermentation and anaerobic digestion (AD) treatment has been developed on pilot scale for urban bio-waste conversion into volatile fatty acid (VFA) and biogas. The specific waste mixture was composed by the pre-treated organic fraction of municipal solid waste (OFMSW) and waste activated sludge (WAS), both produced inside the Treviso (northeast Italy) municipality. The effect of temperature (37 °C and 55 °C) was investigated in both steps. Only the mesophilic fermentation process provided a VFA-rich stream (19.5 g COD VFA /L) with stable physical-chemical features, with no need of chemicals addition for pH control. The sludge buffering capacity made this step technically feasible. The AD step was performed on the solid-rich fraction of fermented bio-waste, after dilution with excess WAS. No relevant differences were observed under the two investigated temperature: in the steady state (organic loading rate of 2.5 kg VS/m3 d), the specific biogas production was 0.40 and 0.45 m3/kg VS at 37 °C and 55 °C respectively, with similar CH 4 content (63–64% v/v). The scaled-up version of the system (in an average urban municipality of 170,000 Person Equivalent) revealed that the whole process is thermally sustainable if both reactors are operated at mesophilic temperature: 36% of surplus thermal energy and 13,03 MWh/d of produced electricity, which corresponds to a revenue of 609,605 €/year. In addition, 2,262 kg COD VFA /d are available for parallel purposes, such as the synthesis of bio-products with higher added value than bio-methane (e.g. biopolymers). Highlights • An innovative route for feasible and profitable urban bio-waste management. • OFMSW-WAS fermentation does not require pH-control at mesophilic temperature. • The overall urban bio-waste treatment process is energetically sustainable at 37 °C. • A surplus of 2,262 kg COD VFA /d is produced for bio-products synthesis. [ABSTRACT FROM AUTHOR]