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Laser wireless power transfer (LWPT) technology holds significant promise for wireless power transmission in space, necessitating that high-efficiency GaAs laser power convertors (LPCs) have strong tolerance to high-energy particle radiation. Therefore, the degradation characteristics of GaAs LPCs with different architectures under 1 MeV electron irradiation were investigated. Experimental and simulation results demonstrate that LPCs with thicker bottom cells suffer from significantly more electrical degradation. The degradation is primarily due to a reduction in electron concentrations in the base of the bottom cells, which is considerably less pronounced as the thickness of the bottom cells decreases. Based on these analyses, thinning the thickness and optimizing the doping profile for the bottom cells are proposed to improve the radiation resistance of the LPCs. Simulations show that the electrical degradation of the optimized four-junction LPCs is notably less than that of the original four-junction LPCs under the same irradiation conditions, indicating that the proposed strategies effectively enhance the radiation resistance of the LPCs. • Electron irradiation-induced degradation characteristics of GaAs LPCs with different architectures are studied. • Damage coefficients of the minority carrier lifetimes of the LPCs at 808 nm are derived by the tested EQE data. • Degradation of the LPCs is mainly caused by a reduction in electron concentrations in the base of the bottom cells. • Optimizing the thickness and doping profile for the bottom cells are proposed to improve the LPCs' radiation resistance. [ABSTRACT FROM AUTHOR]

In this work, XLPE/MWCNT and XLPE/CB nanocomposites have been prepared in order to investigate AC electric field and water effects on electrical aging of XLPE. The mechanical, AC breakdown strength and AC conductivity were tested and the morphologies after 30 days electrical aging were observed using an optical microscope. The results showed that all samples exhibit excellent insulation properties and mechanical properties. Compared with CB addition, the MWCNT composites exhibit better resistance to electrical aging, with the length of electrical aging-induced microcracks in the MWCNT blends decreasing from 104 to 22 µm, and the width decreasing from 87 to 17 µm, which means a reduction of ∼80% compared of values for neat XLPE in both length and width. However, the XLPE/CB composites have a tendency to promote electrical aging. The mechanism is revealed by comparing the results of the fibrous MWCNTs with the spherical CBs.

This article describes the electrical degradation in the I-V characteristics and the Current Transfer Ratio (CTR) of commercial optocoupler (4N35) exposed to an electron beam. The devices are exposed to an electron beam of various doses and the I-V characteristics of LED and output characteristics of the phototransistor are measured as a function of accumulated electron dose. The result indicates that 10 MeV electron of 1.5 kGy dose results in considerable degradation in CTR. Further, it appears that the phototransistor of the optocoupler is more susceptible to radiation damage than the LED part and care must be exercised when these devices are used for space applications. [ABSTRACT FROM AUTHOR]

Inverse power model (IPM), which is a phenomenological model that can predict the electrical life of crosslinked polyethylene (XLPE) insulation, is commonly used to design the insulation and test voltage of cables. Unfortunately, IPM cannot reflect the physical process of electrical aging, and the parameters have no physical significance, which limits the application range and extrapolation accuracy of IPM. Although the physical models of electrical life based on physical and chemical degradation processes exhibiting high accuracy are available, the equations of physical are complex to be popularized in engineering applications. In this paper, a new physical life model for engineering application is presented based on the relationship between transition-state theory and IPM. The proposed model considers the effects of AC electrical stress and thermal stress on aging. The proposed model is fitted to the life data of AC XLPE cable, thus confirming the validity of the proposed model. [ABSTRACT FROM AUTHOR]

In this work, XLPE/MWCNT and XLPE/CB nanocomposites have been prepared in order to investigate AC electric field and water effects on electrical aging of XLPE. The mechanical, AC breakdown strength and AC conductivity were tested and the morphologies after 30 days electrical aging were observed using an optical microscope. The results showed that all samples exhibit excellent insulation properties and mechanical properties. Compared with CB addition, the MWCNT composites exhibit better resistance to electrical aging, with the length of electrical aging-induced microcracks in the MWCNT blends decreasing from 104 to 22 µm, and the width decreasing from 87 to 17 µm, which means a reduction of ∼80% compared of values for neat XLPE in both length and width. However, the XLPE/CB composites have a tendency to promote electrical aging. The mechanism is revealed by comparing the results of the fibrous MWCNTs with the spherical CBs. [ABSTRACT FROM AUTHOR]

Abstract In AlGaN/GaN HEMTs, electrical degradation occurs due to high-voltage stress operation which can be described by a critical voltage operation by which degradation starts to take place which is irreversible. Our investigation is on how electrical degradation occurs due to physical degradation in the device. In this work using Griffith's Equation and inverse piezo electric effect we have shown how physical degradation affects electrical properties of the device and we have also shown how cracks are generated in AlGaN epitaxial layer of the device. Highlights • Electrical stress applied on AlGaN/GaN HEMT. • Because of electrical stress physical degradation takes place after the critical voltage of material degradation. • As material degradation takes place as a result electrical degradation occurs. [ABSTRACT FROM AUTHOR]

Electrical lifetime of alumina-mesogenic epoxy composite sheet is improved by the addition of mica without reducing thermal conductivity. We developed an electrical tree progression simulation to optimize the composition ratio of four species of fillers (mica and three types of alumina fillers). This simulation is based on the electric field analysis with the use of a two-dimensional finite-difference method. The simulation revealed that the electrical lifetime of the composite sheet increases depending on the amount of mica filler although it is saturated at 1.3 vol. %. The calculated electrical lifetime of the sheet with mica filler is 1.5–2.0 times longer than that of the sheet without mica. This result agrees with the experimental at high applied voltage of 7 kVrms. A low mica ratio is suitable in the view of the thermal conductivity of the composite sheet because thermal conductivity of mica filler is much lower than that of alumina filler. The effective amount of mica filler was determined at 1.3 vol. % to possess high thermal conductivity and long electrical lifetime. As a result, a composite sheet with thermal conductivity of 8.7 W m−1 K−1 and the electrical lifetime 13 times longer than the sheet without mica at 4 kVrms was obtained. [ABSTRACT FROM AUTHOR]

Most of studies are focused mainly on performance degradation analysis of solar cell or categorizing PV failure modes concerning solely climate or cell-technology. However, the impact of degradation modules on output power of PV arrays remains somewhat unclear and has not been reported so far. Therefore, main task of the present work is to get a general view of mismatch effect on PV arrays output for aged panels. Photovoltaic current-voltage characteristics of the 10 individual modules at Research Unit in Renewable Energies in Saharan Medium were measured and recorded. Measurements are based on the analysis of mismatch losses due to series and parallel connection of aged PV modules. Degradation data and the analysis of the I-V characteristics indicate that the tested modules have suffered in the hot desert. Both of visual and electrical degradation data reaffirm the direct relation between observed physical degradation and output power drop. Results and analysis of the I-V characteristics and degradation data indicate that Power losses in crystalline PV modules are also due to mismatch in the I-V characteristics of these modules. The paper provides many findings that can be beneficial in further studies on design of aged PV array and development of a crystalline silicon PV module and can enable the manufacturers to prevent premature failure in desert climates. • The paper provides many findings that can be beneficial on design of PV arrays. • Analysis of outdoor measurements indicates that the tested modules have suffered in desert. • Power losses in PV arrays are due to mismatch in the I-V characteristics of aged c-Si PV module. • Study reaffirms the direct relation between observed physical degradation and PV panels output. • Mismatch losses due to parallel connection can be neglected. [ABSTRACT FROM AUTHOR]

The electrical property of gas diffusion layers (GDLs) plays a significant role in influencing the overall performance of polymer electrolyte membrane fuel cells (PEMFCs). The electrical degradation performance of GDLs has not been reported sufficiently. Understanding the electrical degradation characteristics of GDLs is vital to better fuel cell performance, higher efficiency, and longer service time. This paper investigated the effective in-plane electrical resistivity of a commercial GDL by considering environmental and assembly conditions similar to those in use for the operation of PEMFCs. The effective in-plane electrical resistivity of the GDL, subjected to a series of freeze−thaw thermal cycles, was characterized to study its progressive electrical degradation with thermal cycles. Experimental results indicated that, under low compressive loads, the effective in-plane electrical resistivity of the commercial GDL showed weak anisotropy, and was greatly influenced by the transformation of carbon fiber connection in the porous layer. In particular, the thermal aging treatment on the GDL through the first 100 freeze−thaw cycles contributed a lot to its in-plane electrical degradation performance.

Micro electromechanical system (MEMS) micromirrors are interesting devices to be adopted in pico projector application. In fact, together with laser sources, they can be adopted to obtain an always in focus projected image. The reliability of these devices is not yet been addressed. In this paper, we investigate the reliability of micromirrors subjected to long-term stresses. The preliminary results and their interpretation is addressed at the end of this paper. The results led us to think about two different degradation mechanisms. Permanent and recoverable stiffness variation can both influence the mechanical tilting angle of the device during long-term stresses. These two different mechanisms may affect the correct behavior of the device. Further measurements will be needed in order to validate the preliminary hypothesis made in the last section of this paper. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries are increasingly used in mobile applications where mechanical vibrations and shocks are a constant companion. There is evidence both in the academic and industrial communities to suggest that the electrical performance and mechanical properties of the lithium-ion cells of an electric vehicle (EV) are affected by the road-induced vibration. However, only a few studies related to the effects of vibration on the degradation of electrical performance of lithium-ion batteries have been approached. Therefore, this paper aimed to investigate the effects of vibration on the DC resistance, 1C capacity and consistency of NCR18650BE lithium-ion cells. Based on mathematical statistics, the method changes of the DC resistance and the capacity of the cells both before and after the test were analyzed with a large sample size. The results identified that a significant increase in DC resistance was observed as a result of vibration at the 95% confidence level, while typically a reduction in 1C capacity was also noted. In addition, based on a multi-feature quantity, a clustering algorithm was adopted to analyze the effect of vibration on cell consistency; the results show that the cell consistency had deteriorated after the vibration test. [ABSTRACT FROM AUTHOR]

The damage of glass fiber-reinforced epoxy composites (GFRP) caused by mechanical loads is an important reason for the related electrical breakdown. In this paper, the L-shaped needle-wire electrode is used to simulate the coupling direction of mechanical stress and electric field, and the influences of equivalent tension and compression load on the electrical tree degradation of GFRP are obtained. It is found that both tensile and compressive loads will aggravate the electrical tree degradation in GFRP and reduce the average breakdown time. Under tensile load, the damage area of electrical tree increases, and even the sample breaks at the moment of electrical breakdown. However, the color of electrical tree channels is light and the number of branches is small under compression load. The narrow carbonization channels after breakdown will be accompanied by spherical damage areas. The simulation results of GFRP interface damage confirm that the increase of tension and compression load will lead to different degrees of damage at the fiber-matrix interface, and then cause local electric field distortion. At the same time, the combined action of high temperature and high pressure and external mechanical load will aggravate the electrical tree degradation process of GFRP. [Display omitted] [ABSTRACT FROM AUTHOR]

Lead zirconate titanate (PZT) is widely used in various electro-mechanical devices because of its piezoelectric function. In some of its applications, the piezo ceramic will be subjected to a DC bias. The applied DC bias will stress the PZT ceramic and can undergo an electrical degradation process. This electrical degradation process demonstrates itself as resistance decreases and leakage current increases. Therefore, the electrical degradation phenomenon can severely impact on device performance and reliability. It has been found that, accompany this electrical breakdown process, black spots will appear in the ceramic body. In this paper, the formation and growth of the black spots in a PZT capacitor under DC bias is investigated. The black spot area is further characterized with various analytical methods. Based on previous research, a multi-breakdown model is proposed for explaining the mechanism of black spot growth. [ABSTRACT FROM AUTHOR]

Shingled solar cells based on electrically conductive adhesive (ECA) interconnection have emerged as a commercially viable option for photovoltaic (PV) modules with attractive attributes including no soldering process (lead-free), tight packing with no gap between cells, and resulting efficiency gains. Reliability of such modules is, however, less certain due to the lack of long-term outdoor performance data. Here we report numerical simulation of thermo-mechanical stress in shingled solar cells using finite element modelling, and identify stress concentration in silicon in the interconnect region not anticipated from simpler analytical models. We also present design and fabrication of samples using ECA interconnection with geometry and characteristics that closely match production modules for realistic fatigue testing under cyclic loading. The setup is combined with real-time electrical measurements that permit monitoring of fatigue-induced changes in the electrical resistance of ECA joint. Detailed measurements are presented using samples with different types ECA and varying patterns of the glue-line aimed at evaluating reduced material usage for cost-reduction. This study demonstrates that the sample structure and experimental setup presented here can be effectively used to evaluate electrical and mechanical degradation of shingled PV modules to guide their design process. • A novel sample design for shingled solar cell degradation studies. • Monitoring of electrical degradation under mechanical fatigue. • Large localized stress in silicon close to the shingled joint. [ABSTRACT FROM AUTHOR]

We have investigated the effect of annealing of graphene sheets on the electrical properties of Au/graphene/n-type silicon Schottky diode. Large scale graphene sheets were grown by chemical vapor deposition and then annealed at 300, 400, and 500°C; one sheet was left un-annealed as the control. The diodes were fabricated by transferring the graphene sheets directly onto n-type Si substrates and the current-voltage (I-V) and capacitance-voltage (C-V) characteristics were evaluated. The average values of the Schottky barrier height (SBH) and ideality factor (η) for the as-fabricated Au/graphene/n-type silicon Schottky diode from I-V measurements were determined to be ~0.8±0.01eV and ~1.79±0.05, respectively, whereas the SBH from C-V measurements was ~0.89±0.01eV. The electrical transport characteristics measured at room temperature indicated that annealing of graphene sheet prior to the transfer of the graphene onto the n-Si substrates significantly reduces the electric degradation of the Schottky diodes, even though no distinct differences in other electric properties, including ideality factors and SBHs, before or after annealing of the graphene sheets were observed. Thus, by simply annealing the graphene sheets at 500°C, we found that the Au/graphene/n-type silicon Schottky diode showed an approximately 3.3-fold lower series resistance as compared with the un-annealed Schottky diode under air exposure of up to 7days. These annealed diodes showed significantly reduced electrical degradation by removing the potentially trapped H2O and/or O2 at the interface between the graphene layer and the n-Si substrate. [ABSTRACT FROM AUTHOR]

Abstract: The insulation resistance (IR) and the electrical endurance of Y-acceptor doped (Ba,Ca)(Ti,Zr)O3 ceramics, fired in reducing atmospheres, are significantly improved by a re-oxidation treatment. This effect has been studied by means of impedance spectroscopy (IS). Insulating grain boundary barrier layers were detected also without interaction with Ni-inner electrodes, as they are applied in multilayer ceramic capacitors (MLCCs). In moist firing atmospheres H2O vapor was found to react with oxygen vacancies, forming positively charged hydroxyl defects on regular oxygen sites in the crystal lattice. Hopping of protonic defects is supposed to raise the ionic conductivity. Re-oxidation in dry gas mixtures of O2 and N2, however, desorbs water from the dielectric material and improves the IR. DC-field stress heavily degrades the grain boundary barriers. Protons in the dielectric material largely accelerate the electrical degradation. Hydroxyl defects are also considered to be responsible for alterations of the dielectric temperature characteristics at the Curie point. [Copyright &y& Elsevier]

Highlights: [•] Correlation between IBIL and surface electrical degradation. [•] Potential to remotely monitor degradation of insulating materials. [•] Possibility for in situ recovery of the insulating properties by thermal annealing. [Copyright &y& Elsevier]

In order to understand aging mechanism of solid insulating materialscaused by surface flashover, this paper presents the electrical degradation characteristics of cross linked polystyrene (XLPS) by repetitive impulse surface flashovers in vacuum. The surface of samples underwent flashover repeatedly under different impulse voltage situations. Each flashover voltage and current was recorded, and the flashover energy was calculated to present flashover properties under each condition. Experimental results indicate that there are different degradation phenomena of XLPS after undergoing those impulse flashovers. The flashovers with small current have positive effect on surface flashover property of insulating material. However, the large currents when flashovers occurred play a destruction role in surface properties of XLPS. It is said that finite numbers of repetitive impulse flashovers under small flashover currents removed the contaminants, water and gas on the sample surface. In addition, it represents a "conditioning" effect and stable situation of flashover properties under these situations due to removal of emission sites, micro protuberance of electrodes and sample surface, especially at the cathode triple junction. However, repetitive flashovers under high flashover current (≫1 kA) led to surface degradation. This phenomena attributes to the high flashover energy changed the sample surface state, destroyed the sample surface and formed apparent carbonized channels and regions on sample surface. So flashover becomes unstable in this situation. Through summarizing and analyzing the experimental results, the flashover energy was proposed as a main factor to characterize the phenomenon of degradation by repetitive impulse flashovers in vacuum. [ABSTRACT FROM AUTHOR]

Aluminum-doped zinc oxide (AZO) thin film is a promising candidate for low-cost transparent conductive oxide applications. AZO thin films have good electrical and optical properties; however, their reliability must be carefully considered in manufacturing and usage of flexible devices such as flexible solar cells. Cyclic bending leads to both electrical and optical degradation of AZO thin films. Therefore, this paper was designed to investigate the effects of the bending frequency, bending diameter, number of bending cycles, and film thickness on the electrical and optical degradation of AZO films, which were deposited on polyimide (PI) substrates using a radio frequency–magnetron sputtering technique. The cycling was conducted on identical specimens under controlled study parameters. The design of experiments technique was used to determine the significant factors on the percentage change in electrical resistance (PCER) and the degradation of average transmittance (DAT), considering a wavelength range from 660 to 950 nm. The result shows that the PCER is very sensitive to number of bending cycles, particularly in the first 300 cycles. After 1000 cycles, the mean PCER of 425- and 600-nm AZO films are about 300 \% and 600\%, respectively. The DAT is sensitive to number of bending cycles, bending diameter, and bending frequency. The mean DAT is about 2.8\% after 1000 bending cycles. [ABSTRACT FROM PUBLISHER]

Among the various factors influencing the service life of the electric equipment, the performance of dielectric insulation materials has an important role to determine their whole service life. Degradation of insulating materials is fatal to insulation breakdown and finally lead to stop their operations. So the evaluation methods for the degree of degradation and aging for solid, oil and gas insulation have been developed and utilized very effectively to determine their performances. In order to determine the degradation of insulating materials immersed in extremely low temperature media such as liquid nitrogen, the abrupt temperature change from cryogenic to normal room temperature should be considered. But the assessments of low-temperature aging test method for the dielectric materials immersed in liquid nitrogen considering these conditions were not fully reported. Therefore, for the fundamental step to establish the suitable degradation test methods for cryogenic dielectric materials, we focused on the evaluation of aging test methods for dielectric materials exposed to low temperature environments considering thermal shock by cool-down and warm up test, thermal stress test and electric field stress test. In order to verify the effect of various degradation methods on cryogenic dielectric materials, Kraft, Kapton(polyimide) and Nomax type 410 sheets have been prepared and degradation experiments have been conducted. Then dielectric breakdown tests were performed. According to the test results, it was found that thermal shock degradation could be effective factor determining the degradation of cryogenic dielectric materials. [ABSTRACT FROM AUTHOR]

Abstract: Lead zirconate titanate (PZT) is widely used in electromechanical devices such as ultrasonic transducers, sensors, ultrasonic motors, actuators and resonators. In harsh operating environments such as high humidity and high temperature the electrical resistance of the ceramic can decrease resulting in leakage currents. These can have a significant impact on device performance, particularly for low power applications. In this paper, the increase in leakage current is investigated and characterised under high humidity conditions. It is observed that the leakage current does not evolve smoothly over time, but is characterised by current transients. Detailed measurements of these current transients are reported, and their relationship to the conduction processes in the ceramic is investigated. A mechanism of conductive channel formation is proposed to account for the leakage current increase and current transients. [Copyright &y& Elsevier]

Abstract: The effects of thermally annealing Bi–Mn–Co–Sb2O3-added ZnO varistors on their electrical degradation were investigated. For the samples added with 0.01mol% Sb2O3 and without Sb2O3, no marked difference in the nonlinearity index α of the voltage–current (V–I) characteristics was observed upon electrical degradation for the annealed and nonannealed samples. Upon increasing the amount of Sb2O3 added, the values of α increased after electrical degradation for the annealed samples. Moreover, the value of α after electrical degradation was proportional to the width of gauss function (width) of the X-ray diffraction peak for Zn2.33Sb0.67O4-type spinel particles under various annealing conditions. The added Sb2O3 did not dissolve in the ZnO grains but became segregated at grain boundaries. Therefore, it is speculated that the increase in the width of the spinel particles is due to the increase in the numbers of fine spinel particles at grain boundaries and triple points. Furthermore, it is suggested that the improvement of the electrical degradation is due to the decrease in the mobility of oxide ions or Zn2+ ions owing to their being blocked by uniformly dispersed fine spinel particles at grain boundaries. [Copyright &y& Elsevier]

Abstract: A set of new voltage stabilizers has been synthesized, tested and has shown to suppress a degradation mechanism, i.e. electrical treeing, present in cross-linked polyethylene used for high-voltage cables. Electrical treeing is seen at very high and divergent electrical fields and has a rapid lapse from initiation to total breakdown of the insulation material. The new voltage stabilizers presented in this paper have increased the electrical tree inception field with up to 50% at such low additions as 0.4%-wt. Furthermore, the best-performing materials have also proven to increase the threshold level for tree inception, i.e. before this level no deterioration of the material is seen, up to 50%. [Copyright &y& Elsevier]

The optimal amount of B 2 O 3 (0.75 mol%) drastically improved the electrical properties of Y-doped varistors, reducing the leakage current to 0.8 μA/cm2 while maintaining exceptionally long-term stability against DC electrical degradation and a varistor voltage around 900 V/mm. Boron ions were found with Bi ions in Y-compounds, which contributed to formation of a Bi-rich glass phase containing B at grain boundaries when the B 2 O 3 content was above 0.75 mol%. The change in microstructure affected the donor density and barrier structure, leading to a change in electrical properties. The Bi-rich phase first reduced the Co concentration in the ZnO grains, thereby decreasing the donor density N D. When large amount of B 2 O 3 was added, some Co remained in ZnO grains, causing an increase in N D. A new analytical method using the differential resistance R D for the nonlinear voltage–current density relation was proposed to clarify the effects of B 2 O 3 addition. This method separates the three differential resistance R D i values (i = 1, 2, 3) and was used to analyze the corresponding conduction process in forward-biased region I, reverse-biased region III, and interface region II of the energy band. The R D1 and R D2 values exhibited junction diode-like behavior in regions I and III. The value of R D2 that correlated with α asMAX and the long-term stability of the varistor and R D3 may be related to region II. • The role of B addition on the properties of Y-doped ZnO varistors was investigated. • A high-voltage Y-doped ZnO varistor with excellent resistance to degradation was made for the protection of UHV systems. • The Bi-rich phase first reduces Co concentration in the ZnO grain and decreases donor density upon B addition. • The optimal amount of B drastically improved the resistance of electrical degradation. • A new successive analytical method using differential resistance to clarify the effects of B 2 O 3 addition is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Electrical insulating performance of Er2O3 coating samples with thicknesses of 1.0–2.4μm have been examined under 1MeV H+ and 2.8MeV He+ ion beam irradiations at room temperature. The intrinsic conductivity of one sample has not changed significantly after the irradiation corresponding to the estimated damage of 2.2×10−2 dpa (displacement per atom). A strong electric field of 1kV/mm applied under the irradiation has not affected the conductivity of the sample. In the other sample, the intrinsic conductivities measured after irradiations have increased gradually with the ion fluence, while the estimated damage was as low as ∼1×10−3 to 1×10−2 dpa. Since significant change was not observed in the beam-induced conductivities measured under beam irradiations, local current paths might be generated in the coating layer or at small pits observed on the coating surfaces due to the irradiations. [Copyright &y& Elsevier]

In this study, the optical properties as well as mechanical and electrical degradation of low-density polyethylene (LDPE)/polypropylene fiber (PP fiber) (10–50% PP fiber), polypropylene (PP)/PP fiber (10–50% PP fiber), and LDPE/diamond (0.1–3% diamond) blends, which are prepared by hot pressing method, with changing thicknesses ranging from 30 to 225 µm, are compared. The spectra, in the wavelength range 200–2500 nm, are examined. Based on optical absorption spectra obtained, Tauc graphs are plotted. Determined values of the direct optical energy gap (E), the indirect optical energy gap (E), the width of the band (ΔE), and ultraviolet transmittance (TUV) are listed. The direct E and indirect E values for organic blends are in the range of 3.10–3.17 eV and 1.52–2.99 eV; for inorganic blends they are 1.80–4.13 eV and 1.55–4.7 eV respectively. The electrical strength (ε) and the mechanical tension (σ) have been investigated, and graphs (the dependence of the electrical life time log τε on ε) are given. The experimental results are analyzed from the viewpoint of the validity of the thermofluctuation theory. LDPE and LDPE/0.5% diamond composite parameters consecutively changed: σ from 68 to 82 MPa, ε from 60·106 to 85·106 V/m, mechanical lifetime τσ from 10 to 1.5·105 sec, electrical lifetime τε from 2· 103 to 2·105 sec, and structure-sensitive parameters γ and χ — from 1.48 to 1.18 (J)MPa/mole and from 0.97 to 0.70 (J)Vm−1/mole respectively. The values of mechanical and electrical durability were observed to increase by 20 and 41%, respectively, for LDPE/0.5% diamond composite. [ABSTRACT FROM AUTHOR]

The effects of the electrical degradation characteristics and microstructure of Sb2O3-added ZnO varistors were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersion X-ray spectroscopy (EDX), optical microscopy, X-ray diffraction (XRD), and voltage– current (V-I) characteristic measurement. The nonlinearity index α of the V-I characteristic for Bi-Mn-Co-Sb2O3-added ZnO varistors decreased with increasing amount of Sb2O3 after electrical degradation. Twin crystals of ZnO were formed by the addition of Sb2O3. The number of twin crystals with two c-axes perpendicular to the twin plane increased and the number of twin crystals with two c-axes parallel to the twin plane decreased with increasing addition of Sb2O3. It is suggested that electrical degradation is affected by a combination of orientations of ZnO grains containing twin planes and that a double Schottky barrier may not be formed in the twin plane. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 1– 9, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20493 [ABSTRACT FROM AUTHOR]

Abstract: We systematically investigated intrinsic and extrinsic thermal reactions at TiN/HfSiON gate stacks. The formation of an ultrathin TiO2 interlayer was found to be an intrinsic reaction at the metal/insulator interface, but growth of SiO2 underlayers between HfSiON and Si substrates, which determines the electrical thickness of metal-oxide-semiconductor (MOS) devices, depends on the structure and deposition method of the gate electrodes. Physical vapor deposition (PVD) grown TiN electrodes covered with W overlayers exhibited excellent thermal stability at up to 1000°C. Formation of ultrathin TiO2 interlayers reduced gate leakage current (I g), and growth of the oxide underlayer was suppressed by less than a few angstroms even for 1000°C annealing. In contrast, we found that halogen impurities within CVD-grown metal electrodes enhance interface SiO2 growth, resulting in deterioration of equivalent oxide thickness (EOT) versus I g characteristics of the gate stacks. [Copyright &y& Elsevier]

The total safe operating area (SOA) of LDMOS transistors is discussed. It is shown that the transistors are subjected to different kinds of stresses, yielding a combination of electrical and thermal degradation and/or failure modes. A methodology to build the total SOA for LDMOS transistors is highlighted and is experimentally verified on a 40-V LDMOS implemented in a [ABSTRACT FROM PUBLISHER]

This paper presents the results of experiments conducted on fiberglass distribution line pole. First, the critical flashover (CFO) voltage of the fiberglass distribution line pole and its combination with polymer and porcelain insulators is given. Then, the data obtained from the study performed on accelerated aging of fiberglass distribution line poles are presented, followed by a discussion of the results. [ABSTRACT FROM AUTHOR]

To understand the breakdown (BD) mechanism in gate oxide of MOSFET, BD evolution is investigated by a conductive atomic force microscope. High electric fields of both polarities are applied to induce a pre-BD degradation and a BD transient. Structural hillocks and negative charges are simultaneously observed at both pre- and post-BD stages. The hillocks show stress-polarity dependence, and the height increases with BD evolution. A flat-band shift caused by negative charges does not depend on stress polarity. Lateral size of the hillocks and the electrical degradation remains similar throughout the BD evolution. Progressive structural evolution of dielectric BD is confirmed, where polarity-dependent Si deformation plays an important role [ABSTRACT FROM PUBLISHER]

The physical and reliability characteristics of strained-Si0.8Ge0.2 MOS capacitor and strained-Si0.7Ge0.3 MOSFET with Hf-based gate dielectrics prepared by atomic layer chemical vapor deposition are investigated. The thickness and composition of the gate dielectrics are measured by high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy, respectively. The gate leakage current and interface traps of HfO2/Si1-xGex gate structure are slightly higher as compared to the HfO2/Si MOS devices, which is basically caused by the Ge at the interface. The electrical properties of both HfO2/Si and HfO2/Si1-xGex devices can be improved with increasing PDA temperature up to 800°C, which is due to the thicker interfacial layer grown at the interface, even though crystallization also grows with increasing temperature. However, with higher PDA temperature (>800°C), serious crystallization of HfO2 film causes more bulk traps induced electrical degradation. The electrical stress induced degradation of Si1-xGex substrate is slightly higher as compared to the control Si, due to more traps generations at the HfO2/Si1-xGex interface. For MOSFET, strained-Si1-xGex can effectively improve the drain current for about 20% at saturation and 69% at linear region. The higher gate leakage (Jg∼1.4×10-9A/cm2 at 2 V) and lower breakdown voltage (BD∼3.1 V) of Si0.7Ge0.3 pMOS devices are observed as compared to control Si devices (Jg∼7.9×10-12A/cm2 at 2 V and BD∼7.4 V). After the electrical stress, the degradation of drain current and transconductance and the shift of threshold voltage for Si1-xGex PMOSFET are larger than those for control Si devices, implying Ge induced trap generation at the Hf-silicate/Si1-xGex interface. [ABSTRACT FROM PUBLISHER]

An organic SOG, the Hybird-Organic-Siloxane-Polymer (HOSP), has high applicability to ULSI processes, because of the low dielectric constant of about 2.5. However, the HOSP film will be damaged after photoresist removal. The function groups of HOSP will be destroyed by O2 plasma ashing and chemical wet stripper, which leads to electrical degradation. In order to avoid the issue, H2 plasma treatment is proposed to prevent HOSP film from photoresisit stripping damage. It is found that leakage current is decreased significantly and the dielectric constant is still maintained at a low k value even after photoresist stripping. Therefore, H2 plasma treatment is an effective technique to enhance the resistance of HOSP film against photoresist stripping damage. [Copyright &y& Elsevier]

The sensitivity of vertical cavity surface-emitting lasers to electrostatic discharge (ESD) pulses has been investigated under human body model test conditions. Very similar degradation behavior has been found for vertical-cavity surface-emitting lasers (VCSELs) from two different manufacturers, both with proton-implantation for lateral current confinement. For all investigated devices we observed during forward bias stress that the optical degradation precedes the electrical degradation and the forward bias damage threshold pulse amplitudes were only slightly higher than the reverse bias values. At the initial stage of the VCSEL degradation, damage of the upper p-DBR mirror region has been observed without modification of the active layer. During the ESD tests we monitored the electrical and the optical parameters of the VCSELs and measured during forward bias stress additionally the optical emission transients. The optical transients during ESD pulsing enable a fast evaluation of the damage threshold and give also an indication of the time scale of the junction heating during ESD pulses [ABSTRACT FROM PUBLISHER]

A system to provide mechanical stabilization to high temperature BSCCO-2223 superconducting tape by laminating 0.081 mm thick, spring hard, copper foil to both sides with lead-tin eutectic solder has been successfully optimized. This system has been applied as a method to create a strong, windable composite with a minimum of critical current (I/sub c/) degradation. The "as received" conductor is evaluated for physical consistency of width and thickness. Electrical degradation in the strengthened tape as a result of lamination was found to average 24 percent. This was less than the degradation that would have occurred in an unstrengthened tape during subsequent insulation and coil winding processes. The copper can double the ultimate tensile strength of the pure silver tapes. Additionally, pure silver and dispersion strengthened silver matrix tapes are laminated with 0.025 mm thick copper and 304 stainless steel foil to investigate minimization of the cross sectional area of the strengthening component. The stainless steel can increase the UTS of the pure silver tapes sixfold. Mechanical properties and critical currents of these tapes are also reported both before and after strengthening. The I/sub c/ is also measured as a function of strain on the laminated tapes. [ABSTRACT FROM PUBLISHER]

The electrical reliability of lead zirconate titanate (PZT) films was improved by incorporating Mn; the time dependent dielectric breakdown lifetimes and the associated activation energy both remarkably increased with Mn concentration. The correlation between the defect chemistry and the resistance degradation was studied to understand the physical mechanism(s) responsible for enhanced electrical reliability. At lower electric fields, Poole-Frenkel emission was responsible for the leakage current. Beyond a threshold electric field, Schottky emission controlled the leakage. After electrical degradation of a 2 mol.% Mn doped PZT film, no significant change in potential barrier height for injecting electrons from the cathode into the anode was observed. This suggests that the degradation is mostly controlled by Poole-Frenkel conduction via some combination of hole migration between lead vacancies, small polaron hopping between Mn sites, and hole hopping between Pb2+ and Pb3+. No variation in the valence state of Ti near the cathode was observed in degraded Mn doped PZT films, implying that multivalent Mn provides trap sites for electrons and holes; free electron generation due to compensation of oxygen vacancies at the cathode and free hole formation at the anode region might be suppressed by the valence changes from Mn3+ to Mn2+ and Mn2+ to Mn3+ respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

• The mechanism of electrical characteristics degradation of AlGaN/GaN HEMTs was analyzed. • The AlGaN/GaN heterostructures and HEMTs were exposed to 5-MeV protons with a fluence of 1 × 1015p/cm2 to investigate the relationship between the radiation-induced damage in the heterostructure and the electrical characteristics of HEMTs. • The creation of additional defects by interacting protons with pre-existing defects in the heterostructure and secondary particles attributed from the collision of proton and metal contacts were expected as dominant factors. We studied the mechanism of the proton-induced electrical degradation of AlGaN/GaN high electron mobility transistors (HEMTs) through 5-MeV proton irradiation. First, the AlGaN/GaN heterostructure was exposed to protons with a fluence of 1 × 1015p/cm2 to investigate the relationship between the radiation-caused damage in the heterostructure and the electrical characteristics of HEMTs. The HEMTs fabricated on a proton-irradiated AlGaN/GaN heterostructure showed slight degradation in dc characteristics and a positive shift in threshold voltage, compared with the HEMTs fabricated on an unirradiated heterostructure. This indicated that the proton radiation-induced defects in the AlGaN/GaN heterostructure were not dominant factors of characteristic degradation. After additional proton irradiation into both devices, more severe degradation in electrical characteristics was confirmed. The HEMTs fabricated on a proton-irradiated heterostructure showed the largest characteristic degradation in this work. It is expected that the secondary particles, attributed from the collision of proton and metal contacts such as ohmic and schottky, can cause the creation of additional defects, leading to significant degradation of device characteristics. In addition, the pre-existing defects in AlGaN/GaN heterostructures created first proton irradiation can also influence the characteristic degradation of devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] The electrical stress effects have been investigated in Al/Al2O3/n+Si capacitors. [•] Electron trapping and HBD phenomena dominate under substrate injection. [•] Positive charge and defect creation and SBD and PBD failure modes dominate under gate injection. [Copyright &y& Elsevier]

Insulated gate bipolar transistor (IGBT) is widely used in a variety of applications, many of them are safety-critical. The failure of the IGBT accounts for a significant portion of the failures in the converter. An electro-thermal model is useful for predicting the junction temperature in power electronic components and modules. The model parameters change with degradation, but parameters of such models are not readily available in the literature or in the parts documentation. In this work, various combinations of parameters, source voltage, junction temperature, gate voltage, collector current, gate resistance, and frequency are developed and executed, and the electro-thermal model parameters are derived from these experimental results. The change of switching power loss and thermal resistance with degradation is derived from accelerated aging experiments that combine temperature and current. The results show that degradation in the thermal resistance over a period of 9000 cycles can increase the junction temperature by more than 20% compared with the original junction and case temperature difference. Degradation at the die level can cause a 50% increase in the switching power loss compared with the original switching power loss under the same working conditions. The electro-thermal model and parametric degradation model are applied in the sine pulse width modulation (SPWM) simulate circuit to improve the accuracy of temperature prediction after degradation. [ABSTRACT FROM AUTHOR]

The electrical property of gas diffusion layers (GDLs) plays a significant role in influencing the overall performance of polymer electrolyte membrane fuel cells (PEMFCs). The electrical degradation performance of GDLs has not been reported sufficiently. Understanding the electrical degradation characteristics of GDLs is vital to better fuel cell performance, higher efficiency, and longer service time. This paper investigated the effective in-plane electrical resistivity of a commercial GDL by considering environmental and assembly conditions similar to those in use for the operation of PEMFCs. The effective in-plane electrical resistivity of the GDL, subjected to a series of freeze–thaw thermal cycles, was characterized to study its progressive electrical degradation with thermal cycles. Experimental results indicated that, under low compressive loads, the effective in-plane electrical resistivity of the commercial GDL showed weak anisotropy, and was greatly influenced by the transformation of carbon fiber connection in the porous layer. In particular, the thermal aging treatment on the GDL through the first 100 freeze–thaw cycles contributed a lot to its in-plane electrical degradation performance. [ABSTRACT FROM AUTHOR]