Accelerated and Outdoor Weathering of Silver Nanowire Transparent Conductors under Electrical Stress in Pseudo-modules

In realistic applications, silver nanowires (AgNWs) are encapsulated in optoelectrical devices to function as transparent conductors and electrodes. Environmental stressors along with the essential electrical stress are inevitably harmful to the AgNWs inside the devices. Herein, to investigate the degradation behavior discrepancy between materials-level and device-level tests, we adopted pseudo-module to mimic the encapsulation. The pseudo-module allows the application of electrical stress and facilitates the interim specimen access for materials characterization through assembly-disassembly. Indoor accelerated and outdoor weathering tests with applied electrical stress to the pseudo-module encapsulated AgNW networks were performed. The impaired optoelectrical properties and morphological changes of AgNWs due to multiple or individual stressor(s) are investigated. Results indicate UVA exposure at elevated temperature coupled with electrical stress is responsible for the electrical failure of AgNW networks. Sulfidation that depresses optical transparency of AgNW networks is prone to occur at lower temperature. This work provides unambiguous degradation behaviors of AgNWs inside encapsulants, helping to improve the design of AgNWs related optoelectrical devices in the applications of solar irradiation environments.

Study on High Frequency Surface Discharge Characteristics of SiO2 Modified Polyimide Film

Polyimide (PI) can be used as a cladding insulation for high frequency power transformers, and along-side discharge can lead to insulation failure, so material modification techniques are used. In this paper, different doped nano-SiO2 are introduced into polyimide for nanocomposite modification. The results of testing the life time of high-frequency electrical stress along-side discharge show that the 10% SiO2 doping has the longest life time. The results show that: for composites prone to corona, their flashover causes more damage, and both positive half-cycle and polarity reversal discharges are more violent; compared to pure PI, the positive half-cycle and overall discharge amplitude and number of modified films are smaller, but the negative half-cycle is larger; at creeping development stages, the number of discharges is smaller, and the discharge amplitude of both films fluctuates in the mid-term, with the modified films having fewer discharges and the PI films discharging more violently in the later stages. The increase in the intensity of the discharge was greater in the later stages, and the amplitude and number of discharges were much higher than those of the modified film, which led to a rapid breakdown of the pure polyimide film. Further research found that resistivity plays an important role in the structural properties of the material in the middle and late stages, light energy absorption in the modified film plays an important role, the distribution of traps also affects the discharge process, and in the late stages of the discharge, the heating of the material itself has a greater impact on the breakdown, so the pure polyimide film as a whole discharges more severely and has the shortest life.

Investigating stability and tunability of quantum dot transport in silicon MOSFETs via the application of electrical stress

In this work, we experimentally investigate the impact of electrical stress on the tunability of single hole transport properties within a p-type silicon MOSFET at a temperature of T = 2 K. This is achieved by monitoring Coulomb-blockade from three disorder based quantum dots at the channel-oxide interface, which are known to lack tunability as a result of their stochastic origin. Our findings indicate that when applying gate biases between -4 V to -4.6 V, nearby charge trapping enhances Coulomb-blockade leading to a stronger quantum dot confinement that can be reversed to the initial device condition after performing a thermal cycle reset. Re-applying stress then gives rise to a predictable response from reproducible changes in the quantum dot charging characteristics with consistent charging energy increases of up to ≈ 50% being observed. We reach a threshold above gate biases of -4.6 V, where the performance and stability become reduced due to device degradation occurring as a product of large-scale trap generation. The results not only suggest stress as an effective technique to enhance and reset charging properties but also offer insight on how standard industrial silicon devices can be harnessed for single charge transport applications.

Electrical-stress driven oxidation in 940 nm oxide-confined VCSEL

In this work, accelerated stress tests have been performed on oxide confined vertical cavity surface emitting LASER arrays to study the formation of defects degrading the performance of the device. One such defect is an additional oxide volume forming at the oxide aperture edge, which is used for optical and electrical confinement. After producing an additional oxide volume the sample was investigated using transmission electron microscopy to estimate the oxidation speed. To produce further insights into the formation process, the temperature during such a stress test was estimated by experimentally measuring the thermal resistance, and by a thermodynamic transport simulation. Both methods produced very similar results showing a temperature increase of around 22 K for a dissipated power of 3.5 mW per emitter. However this temperature rise is very small when compared to oxidation models found in literature and should not be enough to promote the oxidation. This indicates the presence of a new enhanced oxidation mechanism, which could be connected to corrosion based failure mechanisms reported in literature.

Electrical Characteristics and Reliability of SiCN/ Porous SiOCH Stacked Dielectric: Effects of Deposition Temperature of SiCN Film

Silicon carbonitride (SiCN) films deposited using silazane singe-precursor with different temperatures were capped onto porous carbon-doped silicon oxide (p-SiOCH) dielectric films. Effects on the electrical and reliability characteristics of the fabricated SiCN/p-SiOCH stacked dielectrics were investigated. Experimental results indicated that increasing the deposition temperature of the SiCN film increased barrier capacity against Cu migration under thermal and electrical stress and time-dependence-dielectric-breakdown reliability for the SiCN/p-SiOCH stacked dielectric. Therefore, this study provides a promising processing to deposit a SiCN barrier by elevating the deposition temperature and using N-methyl-aza-2,2,4-trimethylsilacyclopentane singe-precursor, which can be applied to back-end-of-line interconnects for advanced technological nodes in the semiconductor industry. A larger capacitance, however, is the main issue due to a larger intrinsic dielectric constant of the SiCN film and stronger plasma-induced damage on the p-SiOCH film. As a result, the related actions will be taken in the future research to improve this issue.

Signatures of Transient Overvoltages in Low Voltage Power Systems in Tea Factories and Their Implications on Insulation Deterioration and Allied Power Quality Issues

Electrical equipment and supply cables demand a better quality of supply, with the recent advancements in integrated sensitive solid-state controls. Divergently, proliferated heavy inductive motors and some performance additions based on power electronics have introduced power quality issues to the network. Thus, this study mainly investigates the impact of switching transients generated by electromechanical machines in industrial power systems on insulation deterioration while taking transient overvoltages due to capacitor bank switching also to support. Transients with a high rate of rise are likely to catalyze the degradation of the insulation quality and break down the insulating material through ionization. These steeply passing overvoltage stresses let partial discharges ensue, which can attack the insulation over long service. To unveil this danger, 314 common-mode transient waveforms were measured in the electrical machines of five tea factories in Sri Lanka, in a 50 ms measurement window, taken in 55 measuring attempts. Most of the transients observed are in the form of a damped oscillatory waveform tailed by fast exponential collapse. That correlates to insulation degradation having a very steep rise as 30.04 V/ns, the highest at the withering section. When machines are heavily loaded, situations tend to generate transients with high amplitudes. There were transient bursts that spread as 426.3 ms, while 14 ns fast rise times were recorded from withering motors. Unlike electrical resonance and power-frequency overvoltages, electromagnetic switching transients last even less than 100 ms. To underline this, an analysis of the frequency domain of transients was also presented, which proves high density of high-frequency components reaching 107 kHz range. Accepting the fact that frequency and amplitude are always under the influences of innumerable dynamics, the observational evidence of the study endorses that electrical stress built by the transient nature of the factories reduces the life expectancy of electrical insulation.

Thermoplastic Starch–Based Composite Reinforced by Conductive Filler Networks: Physical Properties and Electrical Conductivity Changes during Cyclic Deformation

Conductive polymer composites (CPC) from renewable resources exhibit many interesting characteristics due to their biodegradability and conductivity changes under mechanical, thermal, chemical, or electrical stress. This study is focused on investigating the physical properties of electroconductive thermoplastic starch (TPS)–based composites and changes in electroconductive paths during cyclic deformation. TPS–based composites filled with various carbon black (CB) contents were prepared through melt processing. The electrical conductivity and physicochemical properties of TPS–CB composites, including mechanical properties and rheological behavior, were evaluated. With increasing CB content, the tensile strength and Young’s modulus were found to increase substantially. We found a percolation threshold for the CB loading of approximately 5.5 wt% based on the rheology and electrical conductivity. To observe the changing structure of the conductive CB paths during cyclic deformation, both the electrical conductivity and mechanical properties were recorded in parallel using online measurements. Moreover, the instant electrical conductivity measured online during mechanical deformation of the materials was taken as the parameter indirectly describing the structure of the conductive CB network. The electrical conductivity was found to increase during five runs of repeated cyclic mechanical deformations to constant deformation below strain at break, indicating good recovery of conductive paths and their new formation.

Advanced Soft Defect Screen Methodology for Nano-Scale SRAM Yield Improvement

As technology scales down, the density of Static Random Access Memory (SRAM) devices increases drastically, and their storage capacity grows at the same time. Moreover, SRAMs become more prone to physical defects in each technology node. In addition, resistive defects and parametric defects are increasing which are hard to detect by the conventional test. Thus, the need of effective tests with high fault coverage and low cost increases. In this work, we study the reuse of assist technique (read and write assist) and timing margin control technique, commonly applied to improve the functional margins of SRAM core-cells, to improve the coverage of hard-to-detect marginal defects. This analysis is based on extensive injection of resistive bridging defects in core-cells of a commercial low-power SRAM. We show that assist circuits and timing control circuits can be leveraged to increase the defect coverage can be increases up to 28% at nominal operation voltage by simulation. Some successful case studies are also discussed to demonstrate the efficiency of the proposed electrical stress test methodology.

Damage of Flexible Electronic Line Under Mechanical and Electrical Stress Loading

Flexible printed circuits (FPCs) are widely used in electronic devices such as movable part line or wearable sensor. Inkjet printing is attracting attention because it can draw electric lines of any shape without a photo mask. The mechanical characteristics such as flexibility or durability of electric lines have been evaluated by bending and tensile tests. Moreover, the reliability characteristics of metal particle ink lines under electric current loading have been recently evaluated. However, the electronic line has not been evaluated under both the mechanical stress due to bending deformation and the electrical stress due to electric current. According to scaling down of electric devices, the current density and Joule heat in interconnect line increase and electromigration (EM) damage becomes a serious problem. EM is a transportation phenomenon of metallic atoms caused by electron wind under high-density electric current. Reducing EM damage is extremely important to enhance device reliability. In this study, high-density current loading tests of flexible electronic line were conducted under bending deformation of the substrate in order to investigate the effect of mechanical stress on the EM damage of the electronic line. As the results of current loading tests, the specimens with bending deformation became open circuits in shorter time than that without bending deformation. Therefore, it is considered that the bending deformation is affected on the electric reliability characteristic of the flexible electronic lines reflecting EM damage.