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Metal oxide varistors (MOVs) with steady decrease and continuous increase in power loss are generally distinguished as stable and instable, respectively. In this article, the power loss of modern stable MOVs were found to anomalously increase, when the aging voltage was even lowered. In other words, those MOVs were superficially stable in harsh conditions but instable in mild conditions, which was against common sense. In addition, a crossover phenomenon and an overall deterioration in the current–voltage characteristics were observed in the forward and reverse directions, respectively. The unique aging results were in well consistency with the numerical simulation, where redistribution of ions in depletion layers was involved. For modern stable MOVs with adamant interface states, the formation of “U”-shaped ion distribution in depletion layers resulted in increased barrier height at high voltages but decreased height at low voltages. For an arbitrary MOV, the evolution of power loss during aging was a result of competition between consumption of interface states and re-distribution of ions in depletion layers. Therefore, the power loss might not be sufficient to represent the degradation of MOVs. Quantitative studies deep into the dynamics of point defects of Schottky barriers of MOVs are urgent. [ABSTRACT FROM AUTHOR]

An In0.53Ga0.47As/indium phosphide (InP) avalanche photodiode (APD) with a separate absorption, grading, charge, and multiplication (SAGCM) structure is epitaxially grown by molecular beam epitaxy (MBE). The resulting material is studied using X-ray diffraction (XRD), photoluminescence (PL), and scanning transmission electron microscopy. The activation energy extracted from the dark current of the APD indicates that it is dominated by the generation–recombination (G–R) process. Deep low-temperature PL peaks reveal the existence of an ${E}_{v} + 0.42$ -eV deep energy level defect in the indium–gallium–arsenide (InGaAs) absorber layer, which is considered to be a result of point defects caused by Ga-poor or In-poor MBE growth conditions. The effect of the defect on the dark current is confirmed using numerical calculation methods. [ABSTRACT FROM AUTHOR]

In recent years, rare-earth permanent magnets, including Nd2Fe14B and Sm2Co17, which are used in environments with high radiation, such as in electric motors for space equipment and robots operating in nuclear reactors, have become increasingly important. However, the demagnetization of the rare-earth permanent magnets induced by exposure to radiation has become a serious issue. In particular, when high-energy neutrons collide with the atoms in the magnet, the atoms can be removed and point defects can be generated. The spin fluctuations caused by point defects result in demagnetization of the rare-earth permanent magnets. In this study, we investigate via first-principle calculations, the probability of generation of point defects and the change in the magnetic moment in Nd2Fe14B and Sm2Co17 that occurs as a result of the point defect creation. We find that the generation probability of the point defects is very similar in both rare-earth magnets. The attenuation of the magnetic moment in Sm2Co17 was found to be considerably smaller than that of Nd2Fe14B. Thus, we conclude that the radiation resistance of the magnetic properties of Sm2Co17 is higher than that of Nd2Fe14B. [ABSTRACT FROM AUTHOR]

We investigated the X-ray radiation impact on the performances of “backup” erbium-doped fiber amplifiers (EDFAs) and erbium-ytterbium-doped fiber amplifier (EYDFA). These devices are exposed to the space radiation constraints, unpowered in the “OFF” mode, up to their hypothetic activation during the mission. This atypical profile of use must be considered as it could lead to a higher radiation vulnerability. To carry out this study, active optical fibers differing in terms of radiation hardness have been exposed to steady-state X-rays under different profiles of amplifier use: the gain degradation is measured by varying the pumping conditions, that drive the photobleaching (PB) phenomenon, during the radiation exposure: “ON” (100% ON), “OFF” (0% ON), and “OFF–ON–OFF” with powering 2% or 10% of the time. Our results show that the impact of the pump and its related PB efficiency depend on the selected active fiber to build the amplifier. An important result is that the “backup” EDFA designed with radiation-hardened Ce-doped fiber does not suffer from an extra-degradation due to the “OFF” mode, contrary to the one designed with a nonrad-hard fiber. For this latter one, it is indeed possible to reduce the extra-gain degradation by powering the amplifier for short time periods during the “OFF” state; otherwise, the EDFA recovers this extra-gain degradation in a few hours after turning “ON” in our test conditions. For the tested radiation-tolerant EYDFA, an enhanced vulnerability is observed for the “OFF” amplifier, that can be reduced too by briefly powering the amplifier. The origins of these effects are discussed based on the properties of point defects related to the aluminosilicate (EDFA) and phosphosilicate (EYDFA) glasses of the fiber. [ABSTRACT FROM AUTHOR]

Ge-doped optical fibers (OFs) are considered radiation-tolerant waveguides. Even if their transmission in the infrared (IR) domain is degraded under irradiation, for most of the applications, their radiation-induced attenuation (RIA) remains acceptable. Space harsh environment is characterized by low dose and dose-rate constraints meaning that germanosilicate fibers are often employed for data links. However, the temperature can largely vary in space and is known to impact the RIA levels and kinetics. We studied here systematically the combined temperature and radiation effects induced on the transmission, at the telecom wavelengths, of a Ge-doped fiber, between −80 °C and 80 °C up to a total ionizing dose (TID) of 10 kGy(SiO2)–1 Mrad. Our measurements highlight larger RIA levels at low temperatures than at room temperature (RT). At our highest TID, it increases by a factor of ~40 and ~20, respectively, at 1310 and 1550 nm, when the irradiation is performed at −80 °C instead of RT. A model is reported to study the activation energy of the radiation-induced point defects responsible for the IR-RIA. This simple model could help in predicting the fiber vulnerability for various mission profiles. [ABSTRACT FROM AUTHOR]

The effects of a single point defect on InAs gate-all-around nanowire tunnel FETs (NW TFETs) are investigated. We considered two kinds of interfacial defects, the arsenic dangling bond (AsDB) and the arsenic antisite (AsIn). The critical physics related to the point defects, which are the charge trapping (CT), the trap-assisted tunneling, and their interplay, are rigorously captured using the full quantum transport model with the physical defect Hamiltonian obtained from the density functional theory calculations. We found that both defects on the NW cause the bandgap states, which crucially affects the TFETs performances. Through nonequilibrium Green’s function method self-consistently coupled with Poisson’s equation, the characteristics of the point defects under finite bias conditions are analyzed. We found that the CT is strong in AsIn, and thus the defect level, referenced to the valence band edge, is significantly changed by the gate bias. The strong CT leads to the screening of the gate field, which makes the defect level of AsIn effectively pinned near the drain Fermi level. The radial distributions of the density of states (DOS) and the phase relaxation time are analyzed. AsIn shows the strongly localized DOS at the defect center, while the DOS of AsDB is relatively delocalized due to the coupling with the valence bands. The impact of the defects on the TFET performances is examined as the gate length is scaled down. It is shown that AsIn acts as a limiting factor for scaling down of the TFETs. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) devices have shown substantial promise in realizing ultrahigh-voltage and high power, and have been usually considered as a potential candidate for high radiation levels applications. However, in this work it is found that the SiC P-intrinsic-N (PiN) diodes are sensitive to the electron irradiation, which exerts significant influence on the device characteristics. The physical mechanisms behind these behaviors are studied by probing the production of point defects and the evolution of carrier lifetime in the SiC epilayers after irradiation. It is found that the forward current is significantly reduced by irradiation and the specific on-resistance monotonously increases with the increasing electron fluences, which is resulted from the deteriorated conductivity modulation effects in the epilayer due to the enhanced carrier recombination from the radiation induced deep-level defects, such as the carbon vacancy (VC), silicon vacancy (VSi) and VC+VSi complexes. Inversely, no significant change is observed in the reverse leakage current of 4H-SiC PiN diodes, and the breakdown voltage even slightly increases after electron irradiation, which are ascribed to the suppressed carrier generation arising from the point defects in 4H-SiC with a wide bandgap and the carrier-removal effects caused by the acceptor like point defects generated during irradiation, respectively.

The impact of a single displacement defect on the performance of tunneling field-effect transistors (TFETs) is studied. The OFF-state leakage current and subthreshold swing of the TFET are found to degrade by the single point defect. The degradation depends on the trap energy level; the impact due to a deep trap is greater than that due to a shallow trap. The degradation becomes more profound as the defect location moves a certain distance from the source into the channel. The ON-state current is nearly unaffected by the same defect. The single defect effects were found to be more prominent for thinner channel devices. [ABSTRACT FROM AUTHOR]

According to the characteristics of an actual electromagnetic rail launcher (EMRL), this article points out defects in the traditional dynamic response model of EMRL, proposes an improved dynamic response model, and analyzes its dynamic and stopping response characteristics. On this basis, it presents a fast and accurate numerical calculation method for three-dimensional transient electromagnetic (EM) force of the EMRL and an order-reduced model of EMRL dynamic response. Furthermore, the second development of commercial software leads to the establishment of an interior ballistic simulation model with EM-structural coupling. The model is used to analyze the interior ballistic characteristics of the EMRL under sequential discharge and continuous firing. The finding is that the dynamic response of the first launching rail will cause a deformation in the second launching rail, in which a greater fluctuation happens. When the time interval between successive launches reaches 1.0 s, the deformation of the second launching rail will no longer be affected by the dynamic response of the first launching rail. [ABSTRACT FROM AUTHOR]

The so-called canonical optical fibers (OFs) are samples especially designed to highlight the impact of some manufacturing process parameters on the radiation responses. Thanks to the results obtained on these samples, it is thus possible to define new procedures to better control the behaviors of OFs in radiation environments. In this article, we characterized the responses, under steady-state X-rays, of canonical samples representative of the most common fiber types differing by their core-dopants: pure silica, Ge, Al, and P. Their radiation-induced attenuation (RIA) spectra were measured online at both room temperature (RT) and liquid nitrogen temperature (LNT), in the energy range [~0.6–~3.0] eV (~2100–~410 nm), highlighting the RIA growth kinetics during the fiber exposure up to an accumulated dose of ~200 Gy(SiO2) at a constant dose rate of 100 mGy/s at RT. At LNT, the deposited doses varied between 100 and 180 Gy, with a time-dependent dose rate. In order to understand the origin of the excess losses and the difference between the RIA spectral shapes observed at the two temperatures, spectral decomposition of the optical losses has been performed using a set of Gaussian absorption bands related to the already known point defects. As a result, if the RIA in the visible domain is quite well understood, the knowledge of the RIA origin in the near-IR remains incomplete, justifying new and deeper studies to clarify the response of the fibers under steady-state irradiation. [ABSTRACT FROM AUTHOR]

The radiation response of a phosphorus-doped multimode optical fiber is investigated under both transient (pulsed X-rays) and steady-state (γ- and X-rays) irradiations. The influence of a H2 preloading on the fiber radiation-induced attenuation (RIA) in the 300–2000-nm wavelength range has been characterized. To better understand the impact of this treatment, online behaviors of fiber samples containing different amounts of gas are compared from glass saturation (100%) to less than 1%. In addition to these in situ experiments, additional postirradiation spectroscopic techniques have been performed such as electron paramagnetic resonance or luminescence measurements to identify the different point defects responsible for the induced losses and their H2 dependence. All our data at room temperature (RT) highlight a strong positive impact of H2, even at very low concentrations, on the RIA. Hydrogen quickly passivates (t < 1 s) most of the defects responsible for the visible–near-IR RIA, mainly phosphorus oxygen hole centers (POHC) and P1 defects. However, 1 year after the H2 loading at RT or when operating at liquid nitrogen temperature, the RIA levels of the not-treated and H2-loaded fiber become comparable. The obtained results provide a better understanding of the potential and limitations of H2-loading treatment to design radiation-hardened fiber links. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) has shown substantial promise in the fabrication of high-power devices, and SiC Schottky diodes and field-effect transistors (FETs) have been considered as potential candidates for outerspace and sensors applications. Due to the multipolar structure, SiC gate turn-off thyristor (GTO) device is relatively sensitive to the irradiation-induced point defects. However, how SiC GTO devices perform under neutron irradiation still needs to be clarified. In this paper, the effects of neutron irradiation on the static and dynamic switch characteristics of high-voltage 4H-SiC GTOs are investigated for the first time. For the static electrical properties, it is found that the forward current significantly decreases with the increasing neutron irradiation fluence. While the cathode leakage current in the blocking characteristics shows an insignificant change up to a neutron fluence of ${1.0} \times {10}^{{13}}$ n/cm2. For the switching characteristics, both the pulse peak current and di/dt show substantial reduction as the neutron fluence increases while the delay time increases after irradiation. The degraded performance of the static and dynamic characteristics of SiC GTO devices was then analyzed and attributed to the weakened conductivity modulation and reduced carrier injection efficiency into the drift layer. These two aspects originate from the significantly reduced carrier lifetime and deteriorated forward characteristics of anode-gate diodes, respectively. [ABSTRACT FROM AUTHOR]

We investigate the vertical leakage mechanism in metal–organic chemical vapor deposition-grown carbon (C)-doped AlGaN/GaN High Electron Mobility Transistors (HEMTs) on 6-in silicon wafer. Substrate bias polarity-dependent ${I}$ – ${V}_{s}$ , temperature-dependent fitting, and band diagram analysis pointed to the Poole–Frenkel (P–F) type of conduction mechanism for vertical transport in the devices with breakdown as high as 580 V for a buffer of $\textsf {4}~\mu \text{m}$. Trap activation energy of 0.61 eV was estimated from the P–F fitting which matches well with values reported in the literature. We propose that higher dislocation density leads to shallower traps in the buffer and build an analytical model of dislocation-mediated vertical leakage around this. The variation in leakage as a function of dislocation density at a given field is predicted and is found to be the most abrupt in the range from $\sim 10^{\textsf {7}}$ to $\sim 10^{\textsf {9}}$ cm $^{-\textsf {2}}$ of dislocation density. This can be attributed to a sharp decrease in trap activation energy in the above range of dislocation density, possibly due to complex formation between point defects and dislocations. [ABSTRACT FROM AUTHOR]

Magnetism of graphene-based compounds has drawn growing interest owing to its tunability by various defects presented in the compounds. Reduced graphene oxides (rGOs), particularly, provide an ideal playground as they have significant defects and functional groups on their layers. Herein, we propose a green synthesize method, a simple way in preparing rGO from coconut shells. The rGO has been synthesized from coconut shells by thermal reduction process at 400 °C, 600 °C, and 1000 °C followed by an exfoliation process. We found that the rGO sample prepared at 1000 °C (rGO-1000) exhibits stronger room temperature magnetization, where the saturation magnetization increases approximately 35 times as large as those prepared at 400 °C (rGO-400) and 600 °C (rGO-600). The concentration of defects increases and the oxygen-containing functional groups reduce with an increase in the heating temperatures, contributing to the increment in magnetization. The observed results in this paper indicate that defect-induced magnetism of the obtained rGO can be enhanced by controlling the temperature in the reduction process. [ABSTRACT FROM AUTHOR]

Magnetic flux leakage (MFL) response predicting is important for defect estimation. This paper first proposes a concept of basic signal by discovering the combination property of the MFL response. The basic signal can be used to predict the MFL response conveniently by a basic signal combination method (BSCM), which is also innovatively put forward in this paper. In this method, the basic signal is calculated in advance, and the MFL response can be calculated by several transformation and combination operations. Both the simulation and experimental results demonstrate the feasibility of BSCM. Compared with other traditional methods (magnetic dipole method and finite-element method), BSCM shows a good performance on both the computational speed and accuracy. [ABSTRACT FROM AUTHOR]

A computational technique is presented in this paper which improves finite element method (FEM) in solving inverse problems. Subregion method is used to select and isolate the area of interest where design parameters for defect shape are updated. An elastic mesh generator is developed in this paper to generate optimal meshes in the selected area to save connectivity matrix until having the most accurate design parameters. Using subregion FEM in solving inverse problems will help in minimizing processing time and memory usage in addition of reducing solution complexity. A 2-D eddy current testing (ECT) problem of detecting and characterizing the location and shape of a defect by separating the defect from entire domain is used to validate the presented subregion FEM algorithm. The elastic mesh generator is investigated to update the preselected design parameters of the defect in each iteration. This meshing technique adds the specialty of using subregion method in inverse problems where elements and nodes numberings are saved inside and outside the defect region. Both the genetic algorithm and simulated annealing optimization techniques are developed to get the accurate defect parameters. The presented subregion FEM results have been verified computationally using conventional FEM. Excellent results of signals agreement and processing time minimization with a factor of 90% with an accuracy of 98% have been achieved. In addition, the presented subregion FEM algorithm has been verified experimentally using aluminum (T6061-T6) and mild steel plate (0.15%–0.30% carbon and Fe) samples. This experiment is carried using an elongated excitation coil in a fixed position mounted on the top of the sample and tunneling magnetoresistive sensor to measure magnetic field. The measured magnetic fields were used as input to the inverse subregion FEM solver and the machined artificial defects were characterized with excellent accuracy. [ABSTRACT FROM AUTHOR]

In semiconductor manufacturing, a wafer bin map (WBM) represents the results of wafer testing for dies using a binary pass or fail value. For WBMs, defective dies are often clustered into groups of local systematic defects. Determining their specific patterns is important, because different patterns are related to different root causes of failure. Recently, because wafer sizes have increased and the process technology has become more complicated, the probability of observing mixed-type defect patterns, i.e., two or more defect patterns in a single wafer, has increased. In this paper, we propose the use of convolutional neural networks (CNNs) to classify mixed-type defect patterns in WBMs in the framework of an individual classification model for each defect pattern. Through simulated and real data examples, we show that the CNN is robust to random noise and performs effectively, even if there are many random defects in WBMs. [ABSTRACT FROM AUTHOR]

The measurement of magnetic flux leakage (MFL) is widely used as a non-destructive technique for inspecting oil and gas pipelines. In this method, many factors can affect the MFL signal, but the magnetization of the pipeline is a fundamental issue that bears consideration. We investigated the dependence of the MFL signal on the magnetizing state of pipeline samples with respect to both near-side and far-side defects by varying the number of permanent magnets in each pole of the U-core system, varying the distance between the two poles, varying the gap between the U-core system and the surface of the steel plates engineered from a gas pipeline, and varying the depth of the rectangular defects. By systematically controlling the magnetization of the samples, we observed novel behaviors of the MFL signals as a function of defect depth. For samples having above-saturated magnetization, the dependence of the MFL signal can be expressed as a quadratic function for all defect depths. However, for samples having below-saturated magnetization, the MFL signal increases linearly at low-defect depths, but exhibits a quadratic response at high-defect depths. These findings have relevance for both fundamental research and practical applications, and they provide a novel and precise cartography method for accurately quantifying the depth of defects in MFL measurement. [ABSTRACT FROM PUBLISHER]

Wafer maps contain information about defects and clustered defects that form failure patterns. Failure patterns exhibit the information related to defect generation mechanisms. The accurate classification of failure patterns in wafer maps can provide crucial information for engineers to recognize the causes of the fabrication problems. In this paper, we proposed a decision tree ensemble learning-based wafer map failure pattern recognition method based on radon transform-based features. Radon transform is applied on raw wafer map data to generate the new features which are exhibiting the geometric information of failure patterns in wafer map. Decision tree algorithm is applied to build decision tree ensemble and the final decision is made by aggregating the prediction results of decision trees. The effectiveness of the proposed method has been verified by using the real world wafer map data set (WM-811K). [ABSTRACT FROM AUTHOR]

This paper proposes a system called CDID for diagnosing semiconductor fabrication process. CDID can identify the carry-over defect type that contributed to a defective cluster captured by an in-line inspection tool during a specific fabrication processing step. Let Rx be a defective cluster captured by an in-line inspection tool during the fabrication processing step psi . First, CDID would identify the defect type of Rx by comparing the image of Rx with the images in reference wafer maps of previous defect clusters captured at psi . Let dj be the identified defect type. CDID would use rules of inferences for identifying the root cause of dj . CDID would utilize dj as a trigger for the appropriate defect specification rules using the standard rules of inferences. Based on established and well-known causes of defects, CDID composes rule-based defect specifications in the form of propositional logic’s premises. The premises are triggered by applying the inference rules. By applying the defect specification rules recursively using the inference rules, CDID can identify the root cause of dj . The quality of CDID has been experimentally evaluated by measuring its prediction accuracy. Results revealed marked prediction accuracy. [ABSTRACT FROM AUTHOR]

Internal defect, especially the parts of the cavity structure defect, is a challenging task in the field of non-destructive testing and often is falsely detected or undetected in the testing process. Creeping wave is a type of compressional wave, which propagates below the curved surface and is sensitive to surface and near-surface defects. Creeping wave detection provides a possibility to recognize internal defect. In this paper, the detection of cylindrical cavity defect by using the electromagnetic ultrasonic creeping wave was studied through the finite-element method. The sensitivity of creeping wave detection was improved through the design of coil parameters, which concentrate the energy and reduce the oblique incidence beamwidth of shear wave. Three common crack defects were analyzed in the structure of cavity. The results show that creeping wave detection can be used to recognize the defects which are more difficult to be detected in the cavity and the features of the defect are obvious, which provides a novel method for the internal cavity defect detection. [ABSTRACT FROM AUTHOR]

In many cases of on-site PD measurement, it is difficult to acquire the perfect phase angle of the PD signal synchronized with the applied voltage. This paper describes a new method of PD diagnosis which can classify the types of defects for unknown phase-shifted PDs using decision tree method. 327 cases of on-site PD data were collected in the field. 5 valid parameters were extracted and the decision tree-based diagnostic algorithm was used to classify types of 6 PDs and 4 noises clearly. Finally we confirmed the new method of PD diagnosis can be applied to on-site GIS diagnosis. [ABSTRACT FROM AUTHOR]

To achieve the automotive quality for semiconductor devices represented by “zero-defect,” part average testing (PAT) is actively applied to outgoing test. PAT has been generally used on wafer level test. This time we expanded it to package level test and established the method of detecting the characteristic variations and screening out the outliers. Moreover, we suggest a way of thinking about the outliers and consideration on the basis of the actual data analysis. We were especially conscious of the statistical meaning of the outliers which were detected. It has been demonstrated that the expanded PAT to package level test can reject the outliers of characteristics variation even within spec. The outliers in distribution of characteristic variations were detected by maintaining chip traceability. The new method can screen out outliers outside the 6-sigma within spec, and there was a clear inflection point between the distribution of the abnormal data and that of the population. It was assumed that hidden failure devices which had not been rejected as early failure were screened out. Detecting the outlier with the new method can reduce the failure rate to the target. [ABSTRACT FROM AUTHOR]

The ability to rapidly detect both printable EUV mask adder defects as well as mask absorber defects across the entire mask image field is a key enabler for EUV lithography. Current optical wafer-based inspection techniques are only capable of detecting repeater defects on a die-to-die basis for chiplets within the image field. Larger server-type chips that encompass the entire mask image field cannot rely on such a scheme, since the presence of the defect in every die prevents their detection. In this paper, a prototype optical wafer defect inspection methodology designed to detect repeater defects over the entire image field, termed die-to-baseline reference die (D2BRD), is investigated. The sensitivity of this inspection technique is demonstrated and compared to eBeam inspection over a range of defect sizes for both opaque and clear type mask absorber programmed defects. Moreover, the D2BRD methodology is used to monitor printing defect adders present in a lithographic defect test mask, as well as 7-nm BEOL layers. Using defect repeater analysis, SEM review and patch image classification of full chip wafer inspections over several mask cycles, the D2BRD scheme is shown to allow the unambiguous identification of mask adder defects, while suppressing random process defects. This methodology has the potential to define the risk assessment of mask adder defects in the absence of an EUV pellicle, and can play an integral part of the wafer print protection strategy. [ABSTRACT FROM AUTHOR]

Electric shorts down to atomic scale have emerged as the most critical yield detractors in advanced technology process development. In this paper, we demonstrate successful detection by various charging dynamic effects which stem from the transistor level response under electron beam exposure. We found that charging dynamic effects coupled with photon or scan direction are exceptionally useful for critical voltage contrast defect detection. Correlation with other characterization methods on the same defective location from electron beam inspection scan shows consistent results for various shorting mechanisms. [ABSTRACT FROM AUTHOR]

Test quality is critical to eliminate test escapes and to achieve high-reliability large-scale integrated (LSI) devices. This paper proposes a new concept called “physical test coverage” to verify test coverage based on the physical layout of LSI circuits. The physical test coverage is calculated as the ratio between the critical area of all wires in a device and that of wires undetected by LSI tests. From the critical area of undetected wires and the defect density of a manufacturing line, the risk of test escapes can be predicted. To effectively develop LSI tests that can minimize the number of test patterns, undetected wires are prioritized by the critical area related to each wire. Even when the conventional “logical” test coverage is high enough to satisfy the coverage criterion, some LSI devices investigated in this paper showed low physical test coverage depending on the physical layout of the LSI circuit. The concept of physical coverage was applied in the test development of some LSI products, and the test quality was substantially improved, such that 90% of test escapes of a device were eliminated. [ABSTRACT FROM AUTHOR]

We evaluate the potential of the cathodoluminescence (CL) spectroscopy to characterize the nature and the spatial distribution of point defects in the main classes of optical fibers (OFs): Telecom-grade, radiation-hardened, and radiation sensitive. Canonical samples, that are differently doped in their cores (Ge, N, P, Ce) or their claddings (F), have been investigated through CL technique using a 10-keV electron beam. Obtained results are compared with those obtained by photoluminescence spectroscopy. CL benefits and limits are discussed on the basis of the obtained experimental data. CL is shown to be efficient to investigate the kinetics of defect generation and bleaching under the electron exposure, being the unique technique allowing us to determine in situ the spatial distribution of emitting defects in the fiber transverse cross sections. New insights are given for some of the defects related to the Ge, P, Ce and N dopants. [ABSTRACT FROM PUBLISHER]

We report an experimental investigation on the radiation-induced attenuation (RIA) in the ultraviolet-visible domain for Ge-doped optical fibers, during X-ray (10 keV) exposure at different temperatures. The objective is to characterize the impact of the irradiation temperature on the RIA levels and kinetics. Our data highlight that for dose exceeding 1 kGy(SiO2) the RIA spectrum changes with the irradiation temperature. In particular, for wavelengths below 470 nm the RIA depends both on the dose and on the irradiation temperature, whereas at higher wavelengths the RIA depends only on the dose. From the microscopic point of view the origin of this behavior is explained by a larger impact of the irradiation temperature on the Ge(1) defects generation mechanism with respect to the one of GeX defects, which appears as poorly temperature sensitive in the tested range. This finding prevents us from easily establishing a conclusive relation between the generation mechanisms of these two types of defects. The lower content of radiation induced Ge(1), in fiber irradiated at higher temperature, is supported by the electron paramagnetic resonance (EPR) results acquired after the irradiation. In situ RIA and postmortem EPR data show a significant correspondence of the Ge(1) growth as a function of the dose. Confocal microscopy luminescence experiments indicate that the non-bridging oxygen hole center concentration is higher at 473 K in comparison with those observed at 300 and 373 K. [ABSTRACT FROM PUBLISHER]

This paper presents a three-dimensional modeling study to investigate the effects of one type of soft fault problem in electrical fault diagnosis, the impacts of partial degradation in the coaxial cable shielding or other shielded lines. At first, a time domain nodal discontinuous Galerkin method is used to solve Maxwell's equations and simulate reflectometry responses of soft faults. Then, the numerical simulation results for soft defects in cable shields are compared with experimental measurements for validation purposes. Finally, the shield defects that can arise on coaxial cables are modeled by an equivalent circuit and compared to illustrate their impacts on the electrical characteristic parameters as a function of their severity. [ABSTRACT FROM AUTHOR]

To predict the negative bias temperature instability (NBTI) toward the end of pMOSFETs’ ten years lifetime, power-law-based extrapolation is the industrial standard method. The prediction accuracy crucially depends on the accuracy of time exponents, n. n reported by early work spreads in a wide range and varies with measurement conditions, which can lead to unacceptable errors when extrapolated to ten years. The objective of this paper is to find how to make n extraction independent of measurement conditions. After removing the contribution from as-grown hole traps, a new method is proposed to capture the generated defects (GDs) in their entirety. n extracted by this method is around 0.2 and insensitive to measurement conditions for the four fabrication processes we tested. The model based on this method is verified by comparing its prediction with measurements. Under ac operation, the model predicts that the GD can contribute to ~90% of NBTI at ten years. [ABSTRACT FROM PUBLISHER]

We studied the magnetic properties and domain wall (DW) dynamics of Fe47.4Ni26.6Si11B13C2 and Fe77.5Si7.5B15 microwires. Both samples present a rectangular hysteresis loop and fast magnetization switching. The linear region of dependence of the DW velocity on the magnetic field in Fe47.4Ni26.6Si11B13C2 sample is considerably shorter. Consequently, we studied the structure of Fe47.4Ni26.6Si11B13C2 sample using X-ray diffraction and atom probe tomography. The results obtained using the atom probe tomography supports the formation of B-enriched precipitates in the interfacial layer and in the metallic nucleus after annealing. [ABSTRACT FROM AUTHOR]

Dark current spectroscopy is tested on twenty CMOS image sensors irradiated with protons, neutrons and various ions at different energies. The aim of this work is to differentiate the effect of coulomb and nuclear interactions on the radiation-induced dark current distribution and to identify the main radiation-induced defects responsible for the dark current increase for each type of interaction. For low-energy protons and low-energy light ions (which produce well-separated low energy coulomb interactions), we find that most of the pixels belong to a quantized dark current spectrum at low dark current. In these pixels, the dark current increase seems mainly dominated by specific point defects such as the divacancy and the vacancy-phosphorus complex. Thus, these simple defects seem to form when the displacement damage is rather low and sparse. On the contrary, for nuclear interactions (with neutrons or high-energy protons) producing high coulomb NIEL silicon PKAs or for low energy heavy ions (also having high coulomb NIEL), the DCS spectrum is not visible and all the pixels belong to an exponential hot pixel tail which extends to very high dark current. In these pixels, the dark current increase is mainly dominated by defects with close-to-midgap energy levels. These defects seem more complex than point defects because they can have many different generation rates (explaining the smooth hot pixel tail) and because they tend to form when the displacement damage is high and dense. [ABSTRACT FROM PUBLISHER]

Defects located at the \text E\rm C - 1.1 (eV) level, which are electro-optically active deep traps, generally have been overlooked since their presence cannot be detected except for those in highly resistive CdTe compounds. The origin of this trap is still debated on whether it is from Te vacancies or from dislocations induced by secondary phase defects in Te. We have grown high-resistivity Te-rich CZT ingots to clarify the origin of the 1.1 eV defects and to analyze the defect levels in the CZT samples by current deep level transient spectroscopy (I-DLTS)and photoluminescence (PL). From the analysis, defect levels such as shallow acceptor/donor, A-centers, Cd vacancies and Te antisite appeared to be in both high and low concentrations of Te inclusions, but the level of 1.1-eV defects exhibited dependence on the density of Te inclusion in the CZT samples. We also evaluated the effect of the 1.1-eV deep-level defects on the detector’s performance in point view of carrier trapping and de-trapping. [ABSTRACT FROM PUBLISHER]

Laboratory studies of composite insulators by means of steep-front impulse voltage tests are presented. The tests were performed on four groups of insulators, i.e. on newly manufactured insulators, on insulators removed from service, on insulators earlier exposed to mechanical fatigue test and on insulators with intentionally introduced technological defects. Extensive results of these investigations indicate that application of steep-front impulses of 4 kV/ns provides a better diagnostic efficiency as compared with the standard testing by means of impulses with steepness of 1 kV/ns. It is shown that the application of 4 kV/ns impulses do not cause any damage to healthy insulators, while defected insulators are identified reliably. A new methodology allowing to assess the status of internal insulation in insulators removed from service is proposed based on the performed studies. [ABSTRACT FROM PUBLISHER]

Defectivity control in semiconductor manufacturing is crucial to improve the product quality and to reduce the production cost. When defects are detected, the objective is to identify the tool that generates them. Tool commonality analysis (TCA) is believed to be an efficient method for defect source identification. The critical element of successful TCA is that multiple entry lots within the same process flow are available for the analysis. Hence, since deployment of dynamic sampling strategies, lots selected for inspection are taken from different process flows at different manufacturing levels. In these cases, the TCA cannot identify the defect source but a set of potentially faulty tools. This paper consists in increasing the number of inspected lots that can be used for the TCA. The approach is a combination of two methods. The first one is the comparable lots identification processed by a sequence alignment algorithm. The second method is the reactive sampling algorithm based on the set covering model, this algorithm consists in sampling the minimal number of lots that cover the maximal number of potentially faulty tools. The industrial experiments of the proposed algorithms show a significant increase of number of available lots for analysis. [ABSTRACT FROM AUTHOR]

Partial discharges (PDs) induced by artificial fixed protrusions inside an SF6 gasinsulated switchgear (GIS) test object under oscillating switching and lightning impulse voltages (OIVs) were investigated experimentally. The features of PD current and light pulses (sequences) under impulses were analyzed. The characteristics of PD behaviors under oscillating lightning impulse (OLI), oscillating switching impulse (OSI) and 50 Hz AC voltages were studied according to their statistical distributions. The experimental data were quantitatively analyzed to compare the effectiveness of AC and OIV voltages in exciting the PDs in terms of PD inception and PD activity. Most PDs occurred successively around the peaks of the oscillation period of OIVs and periodical PD sequences were formed. Compared to positive point PDs, negatives occurred more frequently, but with smaller magnitudes. The positive OSI was found to have relative high efficiency in exciting PDs from fixed protrusion comparing to other types of voltage investigated. The occurrence frequency of PD under negative OLI was one or more orders of magnitude greater than that under AC voltage. The average PD magnitudes under positive OIVs were much greater than the others. Both the average PD magnitude and the occurrence frequency were greater at 0.2 MPa, than at 0.4 MPa. This indicates that the AC PD test is not very sensitive to local enhanced field defects, such as fixed protrusions on conductors, because of the limited PD measurement sensitivity and the corona stabilization under AC voltage. [ABSTRACT FROM AUTHOR]

Corona and spark are two typical discharge types in gas-insulated switchgear (GIS). Studies on the SF6 decomposition characteristics under corona and spark are significant for the safe operation of the GIS. In this paper, the discharge energy/charge and SF6 decomposition products under ac corona with point-to-plane electrode defect and spark with floating potential defect were investigated under different electrode dimensions, applied voltages, SF6 gas pressures, adsorbents and moisture contents. The upper limit of the formation rates, feature extraction, and the amount of wear of the GIS were also discussed. The results show that the influences of gas pressure and moisture content on the discharge energy and SF6 decomposition products under two different defects are distinguishable. In addition, the concentration ratios of (SOF2+SO2)/(SO2F2) under corona and spark lie in the ranges, 0-1, and 1?5, respectively. The formation rates of SF6 decomposition products calculated from experimental results under corona discharge lie in the range, 0.1-5 μmoles/J. However, the formation rates under spark are usually in the range, 0.02-0.04 μmoles/J, which are far lower than that under corona. Theoretically the upper limit of the formation rates under corona and spark are estimated to be in the ranges, 67-540 μmoles/J, and 188- 376 nmoles/J respectively. Besides, the concentration ratios and formation rates can be used to distinguish the discharge types and the amount of wear of the GIS can be estimated. [ABSTRACT FROM AUTHOR]

The dynamics of magnetic vortex in nanodisks with a ring-shaped magnetic defect is investigated using micromagnetic simulations. It is found that a spin-polarized current can drive the vortex core precession, and the presence of the ring affects the final steady oscillation radius Rv and the precession frequency $f$ of the vortex core. Moreover, the precession frequency of the vortex core is sensitive to the size of the ring. In addition, compared with regular nanodisks, the oscillation frequency can be modulated in a wide range for a small exchange stiffness constant A_{r} of the ring. The ring-shaped defect paves a new pathway for regulating the frequency of magnetic vortex oscillators. [ABSTRACT FROM AUTHOR]

Defects which possess rough surfaces greatly affect ultrasonic wave scattering behavior, usually reducing the magnitude of reflected signals. Understanding and accurately predicting the influence of roughness on signal amplitudes is crucial, especially in nondestructive evaluation (NDE) for the inspection of safety-critical components. An extension of Kirchhoff theory has formed the basis for many practical applications; however, it is widely recognized that these predictions are pessimistic because of analytical approximations. A numerical full-field modeling approach does not fall victim to such limitations. Here, a finite element (FE) modeling approach is used to develop a realistic methodology for the prediction of expected backscattering from rough defects. The ultrasonic backscatter from multiple rough surfaces defined by the same statistical class is calculated for normal and oblique incidence. Results from FE models are compared with Kirchhoff theory predictions and experimental measurements to establish confidence in the new approach. At lower levels of roughness, excellent agreement is observed between Kirchhoff theory, FE, and experimental data, whereas at higher values, the pessimism of Kirchhoff theory is confirmed. An important distinction is made between the total, coherent, and diffuse signals and it is observed, significantly, that the total signal amplitude is representative of the information obtained during an inspection. This analysis provides a robust basis for a less sensitive, yet safe, threshold for inspection of rough defects. [ABSTRACT FROM AUTHOR]

Anisotropic materials are widely employed in industry and engineering, and efficient nondestructive testing techniques are important to guarantee the structural integrity of the involved parts. A simple technique is proposed to detect defects in anisotropic plates using ultrasonic guided waves and arrays. The technique is based on the application of an objective threshold to a synthetic aperture image obtained from the instantaneous phase (IP) of the emitter-receiver signal combinations. In a previous work the method was evaluated for isotropic materials, and in this paper it is shown that with some considerations the technique can also be applied to anisotropic plates. These considerations, which should be taken into account in beamforming, are (1) group velocity dependence with propagation direction, and (2) elastic focusing, which results in energy concentration in some propagation directions, with the practical consequence that not all aperture signals effectively contribute to the image. When compared with conventional delay-and-sum image beamforming techniques, the proposed IP technique results in significant improvements relative to defect detection and artifacts/dead zone reduction. [ABSTRACT FROM AUTHOR]

In this paper, a practical rule-based guideline has been presented for on-line detection of partial discharge (PD) defected phase (i.e., phase selection) followed by discriminating PD defected cable section (i.e., localization) in cross-bonded single core cable networks. Both goals are met by relying on the proposed rules that take the advantages of an energy-based index, calculated/measured at different junctions of cable network. The whole process provides practicability needs, as it requires neither synchronized measurements at different junctions of a network nor any PD pulse detection. Moreover, the proposed procedure derives the required indices from the measurements out of the link boxes, which provides enough safety in practical applications. Simulating and investigating four popular cross-bonding schemes (including sectionalized and continuous by coaxial cable and single core cable) as well as various characteristics of PD sources, different source locations, and noisy condition have proven acceptable performance of the proposed method in both tasks of phase selection and localization. [ABSTRACT FROM AUTHOR]

Detection of decomposition products is a newly-emerging method for the condition diagnosis of SF6-insulated equipment. Based on the two grading structures that are commonly adopted in SF6-insulated current transformers (CT), three models consisting of the needle-to-plane, the ball-to-plane, and the plane-to-plane were established. Gas decomposition was investigated in a 90 L discharge chamber under operating conditions. Products were analyzed with gas chromatography (GC) and X-ray photoelectron spectroscopy (XPS). Typical gas decomposition products are CF4, SO2F2, CS2, SO2, and S2OF10. For the needle-to-plane with a gap of 30 mm, near-linear growths with time are observed in the concentrations of SO2F2, SO2, and S2OF10 when the applied voltage is set as 33 kV. Addition of the adsorbent suppresses the concentrations of all three products, especially SO2. Besides, CF4 and CS2 are also found to be the characteristic components of partial discharge involving polyester films. And their concentrations are higher when the electric field lines are parallel to the surface of the polyester. As for the polyester films, the atomic ratio of C decreases, the atomic ratio of S increases, and the atomic ratio of F increases significantly as the deterioration becomes more serious. Moreover, the concentration ratio of S2OF10/SO2F2 in the needle-to-plane is mostly within the range of 0- 2, whether with the addition of adsorbent or not. And the ratio is much higher (2-10) when polyester is involved in the discharge process. It could be used to diagnose the insulation condition of CT effectively. [ABSTRACT FROM AUTHOR]

A means of measuring the yield influence for high density, low kill potential defect mechanisms is presented. The method can be applied to wafers individually and is only, marginally more expensive to implement than a least squares fit, but has a much smaller standard error and provides a clear indicator of impact on yield. The ability to tolerate up to 50% outliers enables the method to analyze zone-based data and consequently be resilient to the presence of systematic yield profiles. This is achieved by focusing on the zone specific, kill ratio per defect. This can greatly improve the estimate of yield impact on priority wafers when affected by a defect mechanism whose density varies wildly between wafers, or confirm the validity of the standard defect classification kill ratios. For wafers with typical levels of defectivity, the method can confirm the results of traditional contingency table analysis, with the added confidence that the results are based on a curve fit to any progressive yield response, rather than a single calculation. [ABSTRACT FROM AUTHOR]

Defect detection and classification in semiconductor wafers has received an increasing attention from both industry and academia alike. Wafer defects are a serious problem that could cause massive losses to the companies’ yield. The defects occur as a result of a lengthy and complex fabrication process involving hundreds of stages, and they can create unique patterns. If these patterns were to be identified and classified correctly, then the root of the fabrication problem can be recognized and eventually resolved. Machine learning (ML) techniques have been widely accepted and are well suited for such classification-/identification problems. However, none of the existing ML model’s performance exceeds 96% in identification accuracy for such tasks. In this paper, we develop a state-of-the-art classifying algorithm using multiple ML techniques, relying on a general-regression-network-based consensus learning model along with a powerful randomization technique. We compare our proposed method with the widely used ML models in terms of model accuracy, stability, and time complexity. Our method has proved to be more accurate and stable as compared to any of the existing algorithms reported in the literature, achieving its accuracy of 99.8%, stability of 1.128, and TBM of 15.8 s. [ABSTRACT FROM AUTHOR]

We investigated the thermal behavior of defects remaining in low-dose ( \boldsymbol <10^\mathbf 13~\mathrmcm^\boldsymbol -\mathbf 2 ) arsenic- and boron- implanted Si after high-temperature (1100 °C) rapid thermal annealing (RTA). The defects remaining after RTA were characterized as vacancy-type defects, and confirmed to be created by nonequilibrium states that occur during the extremely rapid cooling step of the RTA sequence. They were gradually removed by applying additional furnace annealing (FA) (i.e., thermal equilibrium heating process) at 300–400 °C. At the range of 500–600 °C, however, carbon- and oxygen- related point defects were newly created. These defects were confirmed to be eliminated at 700 °C, and the crystal quality was significantly improved. When using a rapid thermal process for heat treatment after low-dose impurity implantation, it is necessary to apply an equilibrium thermal treatment at >700 °C to remove residual damage as well as to activate impurities. [ABSTRACT FROM PUBLISHER]

We investigated the impact of an oxygen preloading on pure-silica-core or fluorine-doped-core fiber responses to high irradiation doses (up to 1 MGy (\SiO_2)). Oxygen enrichment was achieved through a diffusion-based technique, and the long-term presence of \O_2 molecules was confirmed by micro-Raman experiments. Online radiation induced attenuation (RIA) experiments were carried out in both the pristine and the \O_2-loaded optical fibers to investigate the differences induced by this pretreatment in the UV and visible ranges. Contrary to results recently published on the positive impact of \O_2 on infrared RIA, our results reveal a RIA increase with \O_2 presence. Data are analyzed in order to better understand the microscopic processes involved during the irradiation and to evaluate possible hardening developments. [ABSTRACT FROM PUBLISHER]

Using local nucleation field technique, electronic microscopy, and optical microscopy, we studied different kind of defects in glass-coated microwires. We observed variation of Fe and Si content along the microwires and oxygen presence in defective regions on the metallic nucleus surface and indications of chemical interaction between the glass-coating and metallic nucleus. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to precisely classify surface and subsurface cracks and cavities using a feature-based giant magnetoresistive pulsed eddy-current (PEC) sensor. Based on the author’s previous work involving amplitude spectral analysis combined with wavelet decomposition, the power spectral density analysis of the direct differential PEC response, and the reconstructed approximate and detail components of wavelet transform are performed to extract the defect feature. Principal component analysis (PCA) is designed to eliminate the dimensional method, which is identified with the ability to supply the low-dimensional feature. PCA confused linear discriminant analysis and the Bayesian classifier are both applied for defect classification. The experimental results reveal that cracks and cavities on the surface and subsurface can be classified satisfactorily by the proposed methods that have the potential for gauging automatic in situ inspection for PEC. [ABSTRACT FROM AUTHOR]