Film Breakdown Research Articles

Structure and Composition of the Passive Film Studied Using a Combination of X-Ray Photoelectron Spectroscopy, Secondary Ion Mass Spectrometry, and Scanning Transmission Electron Microscopy

Characteristics of the passive film and the ability of an alloy to repassivate in any event of passive film breakdown control the corrosion. Studying the passive film has been of great interest since late 1836 when first-time iron was called altered iron. Significant progress in understanding the passive film composition and factors causing breakdown, pit growth and repassivation has been made over the past several decades. However, the role of metallurgical parameters on the passive film structure, composition, crystallinity, chloride ion interaction needs further research attention. The composition and structure of the passive film in Al alloys and stainless steels have been studied using advanced analytical techniques with high depth and spatial resolution have been presented herein. We have used a combination of time of flight secondary ion mass spectrometry (ToF-SIMS), X-ray photoelectron microscopy (XPS), and scanning transmission electron microscopy to study the passive film and pits. The surface film was studied after potentiostatic polarization as well as immersion tests in NaCl solution with immersion time varying from 30 minutes to four weeks. The crystallinity of the passive film was dependent on the composition and microstructure of the alloy. The incorporation of chloride and its distribution in the passive film was dependent on the material and conditions used to produce the passive film. The thickness of the passive film was found to depend on the microstructure of the underlying substrate. The role of the microstructure on passive film structure, breakdown, and repassivation or pit growth will be discussed.

(Digital Presentation) Enhanced Electrochemical Phosphate Recovery from Wastewater: Implications of Pulsating Anode Potential

Electrochemical recovery of phosphorus (P) as struvite (or magnesium ammonium phosphate hexahydrate, MgNH4PO4.6H2O) fertilizer using a sacrificial pure magnesium (Mg) anode is considered a sustainable strategy to deal with the limited availability of rock phosphate. However, the formation of an electrically passive film of magnesium hydroxide (Mg(OH)2) and/or struvite on the surface of Mg upon immediate immersion in aqueous phosphate solution limits the release of divalent Mg ions and decreases struvite precipitation. The present work highlights struvite recovery by an electrochemical method upon application of a dynamic voltage with a sinusoidal waveform. Our results demonstrate that a dynamic potential, when compared to a constant potential, can enhance the rupture of the passivating film, and facilitate the release of Mg2+ from the metal thereby overcoming the problems related to electrical passivation.Aqueous solutions of ammonium dihydrogen phosphate (NH4H2PO4, 10 mM) at neutral pH were used as test solutions. Mg2+ release was notably increased by ~48% relative to constant voltage applications, which subsequently led to ~20% higher phosphate recovery. Characterization studies including X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicated the presence of struvite in the recovered precipitate. Surface characterization of electrodes using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) also confirms a higher extent of passivating film breakdown in the presence of dynamic voltage.

Effect of N2-Anneal Temperature on Silicon Nitride Film: (I) Time-Dependent Dielectric Breakdown and ESR Evaluations

Silicon Nitride (SiN) film has been used as insulating material in many electronic devices such as capacitors and memories . In this report, the effect of N2 anneal temperature on charge break down (Qbd) of LP-CVD SiN film was electrically evaluated using the time-dependent dielectric breakdown (TDDB) test method, and the variation and the density of defects which exist in SiN film, in the oxide layer between SiN and Si substrate, and at the surface of Si substrate, were investigated using an Electron Spin Resonance (ESR) to reveal the defect behavior related to the trigger of Qbd.SiN metal-insulator-metal (MIM) capacitors were fabricated to evaluate TDDB. A 54 nm dielectric layer of SiN film was deposited at 700 degree-C, using a mixture of dichlorosilane（SiH2Cl2）and ammonia (NH3) gasses, by a LP-CVD vertical furnace. For the lower and upper electrode, a 400 nm polycrystalline silicon films were deposited using a LP-CVD. In order to evaluate the effect of anneal temperature on SiN film breakdown frequency, these samples were annealed in nitrogen atmosphere at temperatures between 700 and 1150 degree-C for 1 hour, using a vertical furnace.Breakdown voltage was measured with a current-voltage tester (HP4071A, Hewlett Packard) for each SiN MIM capacitor. The breakdown frequency was defined as the ratio of failed capacitors to tested capacitors. For the TDDB measurements, a constant current stress of 1.33 A/cm2 was applied to the MIM capacitors with the area of 0.00375cm2, 0.0075cm2, 0.015cm2 and 0.03cm2. For each area, 100 chips were made from one wafer and measured.In Fig.1, SiN film breakdown frequency increases toward a peak at around the N2 anneal temperature of 900 degree-C, then decreases at 1000 degree-C, and at more than 1100 degree-C, the frequency increases again drastically at 1150 degree-C.SiN films for ESR study were fabricated on Si wafer in the same LP-CVD process, and annealed in nitrogen atmosphere at temperatures between 700 and 1150 degree-C for 1 hour, using a vertical furnace.The ESR measurements were performed at room temperature using an X-band spectrometer (JES-RE1X). To improve the signal-to-noise ratio of an ESR signal waveform, we set the accumulation number of magnetic-field (H) sweep about 300 times. Mn2+/ MgO hyperfine lines were used for the g marker, and spin densities were determined by using the standard of known spin content.In Fig.2, Dangling bond density at silicon interface (Pb center) has a peak at 900 degree-C, and those in SiO2 (E’ center) and SiN film (K center) increase with increasing temperature from 1000 to 1150 degree-C. The former phenomena of Pb center coincides with the peak of SiN film breakdown frequency at 900 degree-C, and the latter one of E’ center and K center coincides with the tendency of increasing Qbd frequency at more than 1000 degree-C. Figure 1

Anomalous Behavior During Low Rate Discharge of Li/CFX Cells

Lithium-carbon monofluoride (Li/CFx) D-sized battery cells discharged at very low rates (C/1800) were found to deliver inconsistent capacities. These effects were found to be absent as the discharge rate was increased to C/600. Destructive physical analysis of the cells discharged at C/1800 confirmed the effects of corrosion, manifesting as preferential utilization of the Li anode around the copper current collector, discoloration of the remaining excess Li, and more crucially loss of adhesion to the copper current collector, resulting in a premature completion of discharge. This anomalous behavior may be attributed to the competing corrosion reaction at the Li anode during discharge, whereby Li+ is lost to the electrolyte at a rate that is similar to the competing current-producing charge transfer process. At higher rates, this corrosion process is masked by the more significant discharge current generated by the full cell, which occurs at a much higher rate. The inconsistent capacity delivery may relate to the uneven breakdown of the surface film at these very low rates, where the current density is very low. Experimental data from both D-sized and three-electrode cells describing this effect are presented, as well as possible remedies for cells where very low discharge rates are desired.

P‐11: Effects of Ar Dilution on N2O/SiH4 PECVD for the Growth of Silicon Oxide Thin Films with Improved Breakdown Voltage Characteristics

In order to obtain a robust gate dielectric, the nitrogen atom incorporation in the silicon oxide thin film has been investigated in much prior study in recent years. Silicon oxide thin film deposition is mainly performed using SiH4‐N2O plasma by the Plasma enhanced chemical vapor deposition (PECVD) system. Reducing the N2O/SiH4 gas flow ratio increases the nitrogen content in the film. However, the film uniformity dramatically deteriorates as the N2O/SiH4 ratio is decreased and this issue makes the low N2O/SiH4 ratio condition a challenging area for the process condition. In this study, to overcome this problem Argon (Ar) addition was employed to the low N2O/SiH4 ratio plasma and we found that Ar not only allows the thin film to be uniformly deposited by increasing the plasma density due to the penning effect, but also increases Si‐N bond especially under the ratio of 10:1 condition. Even though the silicon oxide thin film was deposited with low N2O/SiH4 gas flow rate, the film uniformity and breakdown voltage characteristics dramatically improved by Ar dilution. In addition, LTPS p‐channel TFT was fabricated by utilizing the improved silicon oxide thin film as a gate dielectric layer and it showed excellent electrical characteristics. This work would be one of the most practical solutions for robust gate dielectric deposition.

Effect of N2-Anneal Temperature on Silicon Nitride Film: (I) Time-Dependent Dielectric Breakdown and ESR Evaluations

Silicon Nitride (SiN) film has been used as insulating material in many electronic devices such as capacitors and memories. This report electrically evaluated the effect of N2 annealing temperature on accidental charge breakdown (Qbd) of LP-CVD SiN film using the time-dependent dielectric breakdown (TDDB) test method. The variation and number of the defects, existing in the SiN film, in the oxide layer between SiN film and Si substrate, and at the SiN film/Si interface, were investigated using an electron spin resonance (ESR) to reveal the defect behavior related to triggering Qbd. At Si surface (Pb center), dangling bond density reached a maximal peak at an annealing temperature of 900°C, and those in SiO2 film (E′ center) and SiN film (K center) were increased with increasing temperature above 1000°C. These two types of phenomena showed good agreement with the Qbd occurrence dependency on the annealing temperature, as the detected by TDDB.

Connection between micron-sized defects and dielectric strength of poly(dimethylsiloxane) elastomer films

The quality of dielectric elastomer (DE) films is a key factor affecting the reliability of DE actuators. Reported here is the effect of the number of micron-sized defects on dielectric strength (DS) for poly(dimethylsiloxane) (PDMS) DE films. Using the same PDMS formulation but different procedures, we produced two model DE films with a thickness of approximately 50 μm. The two PDMS DE films suitably serve as a good-quality model film (EF1) and a low-quality model film (EF2) for this study, as shown by a large difference in the number of micron-sized defects found using micro-Raman techniques. The internal defects with various micron sizes in the two PDMS DE films can be quantitatively analyzed using an optical flaw inspection technique. According to two-parameter Weibull analysis, our assumption is that EF2 has a bimodal distribution of breakdown field (Eb) consisting of failure mode 1 in the early failure range and failure mode 2 in the late failure range. The values of the electric field (E) at the failure probability of 63.2%, defined as the scale parameter and regarded as DS, are 76.3 V μm−1 for EF1, and 39.1 and 69.6 V μm−1 for EF2, respectively. For the Eb distribution, the shape parameters estimated are 18.3 for EF1, and 4.7 and 10.2 for EF2, respectively. The results support the idea that there are different failure mechanisms between EF1 and EF2. The difference in the total number of internal defects, 12 for EF1 and 92 for EF2 per area of approximately 15 mm × 15 mm, should explain such a large variation in DS and Eb distribution. Our findings show the beneficial use of the quantitative analytical approach for micron-sized defects associated with the quality control and premature breakdown of DE films.

Wire electrochemical trimming the recast layer on René 88DT for aero-engine applications

Surface integrity has an important impact on the fatigue life of aero-engine parts, especially the recast layer formed by electrical discharge machining. Wire electrochemical trimming is a method to remove the recast layer (WECT) by utilizing a wire electrode that sweeps along the surface to remove material through an electrochemical reaction, which can ensure the requirements of accuracy and surface integrity simultaneously. An electric-field model was established to investigate current distributions in the WECT machining zone. The results indicated that when the wire electrode sweeps the surface, to accomplish high-precision WECT, it is essential to control three stages including rapid breakdown of the passive film, complete dissolution of the recast layer, and diminishment of overcut of stray current. To this end, the microstructure and polarization behavior of the René 88DT recast layer was first studied and the breakdown behavior of its passive film was analyzed. Results indicate that the crystallite size of recast layer is far less than that of the substrate, and the passive film of recast layer is more difficult to dissolve. Passive film models were established, revealing that the surface of the recast layer adheres to a loose outer passive film (Ni(OH)2) and a dense inner passive film (TiO, TiO2, Cr2O3). The experimental results were then used to derive the critical conditions for the dissolution of the recast layer: when the current density i > 2 A.cm−2, the recast layer starts to dissolve, and when the electric quantity Q = 500 C.cm−2, the recast layer is completely removed. Finally, the preferred parameters were selected by the critical conditions, and the wire electrical discharge machining surface was trimmed to a smooth surface without a recast layer. This paper is expected to provide research ideas for future high-precision electrochemical fabrication of aero-engine applications.

Accelerating effect of pyocyanin on microbiologically influenced corrosion of 304 stainless steel by the Pseudomonas aeruginosa biofilm

In this study, the influence of exogenous pyocyanin (PYO) on the microbiologically influenced corrosion (MIC) of 304 stainless steel by Pseudomonas aeruginosa was investigated. Under sterile condition, the additional PYO in the culture medium had no effect on the corrosion of 304 stainless steel. In contrast, P. aeruginosa biofilm inoculated in the media with additional PYO resulted in more severe pitting corrosion. EIS and cyclic potentiodynamic polarization results indicated that exogenous PYO promoted the electron transfer efficiency between the P. aeruginosa biofilm and the stainless steel surface. X-ray photoelectron spectroscopy (XPS) and transmission electron microscope (TEM) results further demonstrated that the P. aeruginosa led the breakdown of passive film predominantly by accelerating the bioreductive dissolution of iron oxides.

Breakdown and Healing of Tungsten-Oxide Films on Microelectromechanical Relay Contacts

This work discusses the electrical break down of tungsten oxide films that form on contacting surfaces of tungsten electrodes in micro-electro-mechanical (MEM) relays. Electrical tests were applied to the contacts of 27 devices to measure the voltage, current and charge required to break down the oxide films, and also to measure the change in current through the contacts as the film healed. The oxide breaks down when an average of 58 <inline-formula> <tex-math notation="LaTeX">$\mu \text{C}$ </tex-math></inline-formula> of electronic charge passes through the oxide, which usually requires applying 1&#x2013;2 V to drive 100 nA-<inline-formula> <tex-math notation="LaTeX">$10~\mu \text{A}$ </tex-math></inline-formula> of current through the contact. The tungsten oxide heals quickly in laboratory ambient conditions: applying 0.5 V to a contact immediately after breaking down an oxide results in a contact current greater than <inline-formula> <tex-math notation="LaTeX">$5~\mu \text{A}$ </tex-math></inline-formula>, but the same test only induces 1 nA of current 1&#x2013;5 minutes later. The reduction in contact current with time follows a power law, which is characteristic of charge relaxation in oxides. Additionally, Holm&#x2019;s experiment shows that current conduction through the contacts is dominated by tunneling through an oxide. These facts together suggest that the break down and healing are electrical processes related to trap accumulation and relaxation in the tungsten oxide. [2021-0161]

Reverse bias breakdown and photocurrent gain in CH3NH3PbBr3 films

Perovskite films are promising candidates for fast, sensitive, and large area photodetectors. A gain in perovskite based detectors has been observed in several architectures, but a model describing the underlying mechanism is still missing or at least incomplete. Here, we present measurements of CH3NH3PbBr3 films under reverse bias exhibiting breakdown at 4–5 V and small photocurrent gain ≲ 2, which based on a phenomenological model, we explain tentatively by tunnel-assisted injection from the TiO2 electron transport layer and carrier multiplication, mediated by the electric field due to mobile ions.

Effect of Chloride on the Pitting Corrosion of Carbon Steel in Alkaline Solutions

The effect of chloride concentration on the passivity breakdown of carbon steel in deaerated pH = 13.5 alkaline solution was investigated. The results show that chloride plays an important role for the pitting corrosion of carbon steel. When NaCl the carbon steel is passive but for NaCl < 2 the carbon steel transfers from passive to passivity breakdown. When NaCl passive film breakdown occurs and the passivity breakdown potential (E b ) of carbon steel is linearly-dependent on the logarithm of the chloride activity in the alkaline solution. As predicted by the PDM, the near-normal distribution of is well indicated by the near straight line in the cumulative distribution probability. The analysis in this study gives us a method to calculate the of carbon steel in alkaline solution and its distribution for any given chloride concentration.

Breakdown field enhancement and energy storage performance in four-layered Aurivillius films

In dielectric capacitors, ferroelectric thin films with slim polarisation electric (P-E) hysteresis loops, which are mainly characterised by small residual polarisation (Pr) and large saturation polarisation (Ps) are expected to obtain high recoverable energy density (Ur) and efficiency (η). However, a lower breakdown in ferroelectric thin films usually impedes this result. Here, through the co-doping of La3+ and Pr3+ ions, a larger Ur of 54.27 J/cm3 and high η of 85.6% were obtained in four-layered Aurivillius phase ferroelectric thin films capacitors due to the enhanced breakdown electric field. The doped films annealed at relatively low temperatures showed similar energy storage properties compared with those of the prototype and higher energy storage efficiency compared with that of higher annealing films. In addition, the obtained thin film shows excellent energy storage properties in a wide frequency range, fatigue durability and good thermal stability. These results indicated that four-layered Aurivillius films are promising candidate materials for dielectric energy storage capacitors. The co-doping of double ions was an effective way to improve energy storage performance.

Microstructural, morphological characterization and corrosion behavior of sand cast AlSi10Cu(Fe) alloy in chloride solution

In order to examine the relationship between the microstructure and the corrosion behavior in chloride solution, the microstructure of AlSi10Cu (Fe) sand cast aluminum alloy has been investigated by using different techniques including scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffraction analysis and electrochemical measurements. The microscopic analysis and X-ray diffraction analysis show several phases in addition to matrix phase, including pores and phases at nano- and microscales. The average rate of micropores and nanopores is 4% and 5%, respectively. The nanoparticle size varies between 20 and 150 nm. Plates and corals-like silicon eutectic, rich-Cu phase and Chinese script phase (Al15(Mn,Fe)3Si2) have been observed. Energy-dispersive spectroscopy analyses show the presence of a new phase (Cu61.22 Zn25.39Ni11.85 Al1.54), and the pitting corrosion has been demonstrated to be initiated at the nanopores. The electrochemical measurements exhibited the effect of several elements and porosities on the corrosion kinetics that is controlled by charge transfer and diffusion phenomenon. Wide passive windows, followed by the breakdown of passive film and excessive dissolution, have been observed in 0.3 and 3 wt% NaCl solutions. The electrochemical measurements show a high corrosion rate which does not recommend the use of this alloy in seawater.

In Situ Investigation of Under-Deposit Microbial Corrosion and its Inhibition Using a Multi-Electrode Array System.

Carbon steel pipelines used in the oil and gas industry can be susceptible to the combined presence of deposits and microorganisms, which can result in a complex phenomenon, recently termed under-deposit microbial corrosion (UDMC). UDMC and its inhibition in CO2 ambiance were investigated in real-time using a multi-electrode array (MEA) system and surface profilometry analysis. Maps from corrosion rates, galvanic currents, and corrosion potentials recorded at each microelectrode allowed the visualization of local corrosion events on the steel surface. A marine bacterium Enterobacter roggenkampii, an iron-oxidizing, nitrate-reducing microorganism, generated iron deposits on the surface that resulted in pitting corrosion under anaerobic conditions. Areas under deposits displayed anodic behavior, more negative potentials, higher corrosion rates, and pitting compared to areas outside deposits. In the presence of the organic film-forming corrosion inhibitor, 2-Mercaptopyrimidine, the marine bacterium induced local breakdown of the protective inhibitor film and subsequent pitting corrosion of carbon steel. The ability of the MEA system to locally measure self-corrosion processes, galvanic effects and, corrosion potentials across the surface demonstrated its suitability to detect, evaluate and monitor the UDMC process as well as the efficiency of corrosion inhibitors to prevent this corrosion phenomenon. This research highlights the importance of incorporating the microbial component to corrosion inhibitors evaluation to ensure chemical effectiveness in the likely scenario of deposit formation and microbial contamination in oil and gas production equipment.

Heavy Loaded Parts of Petrochemical Equipment Destruction Cause Investigation

The problem of using specialized passivating metals and alloys lies in a rather narrow range of the protecting film performance. With a slight change in operating conditions, the film is destroyed and an avalanche-like process of local corrosion begins at the place of film breakdown. A sequence has been developed for determining parts destruction causes, including a sequential analysis of operating conditions; nature of the part destruction; corrosion products composition; phase inversion in the alloy during overheating or mechanical stress in the part.

Volatile products formed during electrical breakdown of polyethylene terephthalate and polypropylene films in high vacuum

In this article we present the results of time-of-flight mass spectrometry of volatile products formed during the electrical breakdown of polyethylene terephthalate and polypropylene polymer films in high vacuum. During the breakdown of films, all the substance emitted from the breakdown channel is a gas of low-molecular products of destruction of macromolecules. The breakdown mass spectra do not contain lines of carbon molecules, the presence of which could indicate carbonation of the channel. To explain the formation of charge carriers, the ionization mechanism of destruction of macromolecules in an electric field is used without the involvement of impact ionization. The final stage of electrical breakdown (the flow of a high-density conduction current) occurs when the critical concentration of traps and electrons ~1024 m-3 is reached. Keywords: electrical breakdown, mass spectrometry, thermodestruction, ionization, macromolecule, trap.

Летучие продукты, образующиеся при электрическом пробое пленок полиэтилентерефталата и полипропилена в высоком вакууме

In this article we present the results of time-of-flight mass spectrometry of volatile products formed during the electrical breakdown of polyethylene terephthalate and polypropylene polymer films in high vacuum. During the breakdown of films, all the substance emitted from the breakdown channel is a gas of low-molecular products of destruction of macromolecules. The breakdown mass spectra do not contain lines of carbon molecules, the presence of which could indicate carbonation of the channel. To explain the formation of charge carriers, the ionization mechanism of destruction of macromolecules in an electric field is used without the involvement of impact ionization. The final stage of electrical breakdown (the flow of a high-density conduction current) occurs when the critical concentration of traps and electrons ≈ 10^24 1/m^3 is reached.

Electrochemical Study on Hydrogen Entry Initiationin SSRT of Low Alloy Steel in High-Pressure Hydrogen Gas

The application of concurrent cathodic hydrogen charging SSRT is being investigated as an alternative to SSRT in high-pressure hydrogen gas, which is used to evaluate the hydrogen compatibility of metallic materials. There are some differences in the stress-displacement behavior and the fracture surface between the two tests. These differences can be attributed to the difference in the timing of the onset of hydrogen entry in the two environments. In SSRT of low-alloy steel in high-pressure hydrogen gas, the amount of absorbed hydrogen up to the yield stress is small and increases rapidly after plastic deformation, Whereas, since in concurrent cathodic hydrogen charging, hydrogen entry is initiated as soon as begins, it is necessary to determine an apporopriate start time. The surface changes of SCM435 specimens during SSRT in NaOH solution were analyzed by electrochemical measurements, and the breakdown of the oxide film that inhibits hydrogen entry during SSRT in high-pressure hydrogen gas was discussed. As a result, the impedance at low frequencies decreased immediately after the yield point, which was attributed to the decrease in the reaction resistance of the oxide film. The rest potential decreased immediately after the yield point and immediately after the fracture, which were attributed to the exposure of the fresh surface due to the breakdown of the oxide film. From these results, it was clear that hydrogen charging in the concurrent cathodic hydrogen charging SSRT should be started just after the yield point.

Electrochemical Method for Producing a TiO2 Film with Photocatalytic Properties

The purpose of this work is to study the production process of titanium dioxide during anode polarization in sulfuric acid and hydrochloric acid solutions. The studies were carried out by recording cyclic voltammogram and by measuring the titanium oxidation current with a change in the voltage between the electrodes. It has been established that with a change in the concentration of sulfuric acid in the range of 50–250 g/l and the voltage between the electrodes in the range of 0–25 V, the magnitude of the titanium oxidation current in-creases and reaches 29.4 mA. With an increase in the concentration of hydrochloric acid from 35 to 100 g/l and a change in the voltage between the electrodes, the titanium oxidation rate increases evenly, but in the voltage range of 10–12 V, a sharp increase in the current magnitude up to 360 mA is observed. A change in the oxidation current indicates an increase in the rate of titanium dissolution. With an increase in the duration of electrolysis, the magnitude of the anode current generally decreases. In all probability, at a voltage of 14 V and higher, a breakdown of the oxide semiconductor film of titanium dioxide is observed in the hydrochloric acid solution. In this regard, a noticeable dissolution of titanium occurs and, subsequently, an oxide film is not produced, but titanium ions are produced. Visual observations have shown that titanium passes into solu-tion in the form of titanium (IV).