Al Deposition Research Articles

Application of a Holed Cathode and Anode Prepared with a Picosecond Pulsed Laser to Lithium Ion Battery (2) ~ Analysis of the Structure of Holed Cathode Layers ~

A holed structure formed in cathodes with a picosecond laser method, which could remarkably improve the high-rate performance, was analyzed with scanning electron microscopy (SEM), Raman microprobe spectroscopy, focused ion beam (FIB)-SEM and mercury intrusion porosimetry. Percussion drilling by the laser beam was adapted to produce holes. During the formation of holes in the lithium iron phosphate (LiFePO4, LFP) cathode layer, a very small amount of LFP was transformed to Fe2O3 by the laser irradiation. The laser evaporated the Al current collectors, and after laser ablation, Al deposits were formed on the sidewall of the holes by the cooling Al vapors. In addition, the laser irradiation caused an increase in the porosity of the LFP cathode layers due to the strong impact of the laser on the LFP layer. The three-dimensional (3D) electron pathway formed by the Al deposits and Al current collector plane and the increase in the porosity of the LFP layers enhanced Li+ ion and electron transfer in the LFP cathode layer, resulting in a remarkable improvement of the high-rate performance of holed cathodes.

In Situ Investigations of Al/Perovskite Interfacial Structures.

Interfacial properties of perovskite layers and metal electrodes play a crucial role in device performance and long-term stability of perovskite solar cells. In this work, we performed a comprehensive study of the interfacial structures and ion migration at the interface of a CH3NH3PbI3 perovskite layer and an Al electrode using in situ synchrotron radiation photoemission spectroscopy measurements. It was found that the Al electrode can react with the perovskite layers, leading to the formation of aluminum iodide species and the bonding between Al and N, as well as the reduction of Pb2+ ions to metallic Pb species at the interface. Moreover, during the Al deposition, iodide ions can migrate from the CH3NH3PbI3 subsurface to the Al electrode, while the reduced Pb remains at the subsurface. The depth profile photoemission measurements, made by varying the photon energies of incident synchrotron radiation X-rays, demonstrate that the reaction occurs at the Al/CH3NH3PbI3 interface at least with a thickness of ∼3.5 nm below the perovskite surface. This study provides an atomic-level fundamental understanding of the Al/CH3NH3PbI3 interfacial structures and insight into the degradation mechanisms of perovskite solar cells when using Al metal as the electrode.

A Promising Fuel for Variable Thrust Motor: HTPB Propellant with High Pressure Exponent

AbstractIn this paper, we developed a HTPB propellant containing energetic compound hydrated‐tetra‐(‐amino‐1,2,4‐triazole) copper perchlorate (ACP) as the fuel for variable thrust motor with the purpose of controlling gas flow. Formulation of the propellant was designed and then various performances of this propellant were investigated. Results show that HTPB propellant containing 2 % ACP has a pressure exponent of 0.57 (static) or 0.56 (dynamic), suggesting an excellent capacity to control the burning rate. Thermal decomposition of ACP and the decomposition of ammonium perchlorate (AP) in high temperature are demonstrated to be sensitive to pressure by PDSC analysis, moreover, decomposition of AP in high temperature (around 400 °C) could be accelerated by ACP, φ 50 mm motors charged with this propellant work stably in the pressure range from 1.18 MPa to 21.72 MPa and less aluminum (Al) deposits in chambers and nozzles. Mechanical performance of the propellant in −40 °C and 20 °C turns out to be excellent with σm≥0.96 MPa and ϵb≥20.92 %, and is better than that in 50 °C. Low impact sensitivity (H50, 72 cm) and friction sensitivity (P, 31 %) of HTPB propellant containing 2 % ACP are found in the security tests, the propellant is also insensitive to shock wave (G50, 23.8 mm).

Aluminum electrodeposition from a non-aqueous electrolyte—a combined computational and experimental study

Electrodeposition of aluminum (Al) from an organic non-aqueous electrolyte of ethylbenzene containing aluminum bromide is demonstrated. It is offered as a simple method for the preparation of Al coatings. This work employs distinct electrochemical techniques and explores the effects of the experimental parameters on the kinetics of the process and the quality of the final coatings. The process presented here enables deposition of pure and crystalline Al at room temperature and facilitates the production of uniform Al coatings on various metallic substrates. Morphological studies establish that the growth of Al deposits follows an island mode, and thus, the most noteworthy effect of the substrate over the morphology of the deposits originates from its impact over the nucleation stage, and the density of islands. This study is complemented by theoretical modeling for the adsorption of Al atoms at the different surfaces. Corrosion evaluation determines the dissolution mechanisms of each of the studied substrates in the examined electrolyte. These findings further corroborate the claim that this electrolyte enables the reversible electrodeposition of Al.

Effect of Aluminum on Lead Release to Drinking Water from Scales of Corrosion Products.

The occurrence of aluminum in scales on lead pipes is common. This study aimed to identify factors that influence Al accumulation on oxidized lead surfaces and to determine whether the presence of Al impacts Pb release from corrosion products to water. Al accumulation and Pb release were monitored both with and without the addition of phosphate as a corrosion inhibitor. Pb coupons with corrosion scales were exposed to chlorinated water for up to 198 days to investigate Al accumulation and Pb release. Al accumulation was facilitated by Pb corrosion products, but its accumulation was inhibited by phosphate addition. During the study period, the formation of Al deposits did not affect Pb release when phosphate was absent. In an Al-free system, the addition of 1.0 mg/L phosphate (as P) lowered the dissolved Pb concentration below 1.0 μg/L. In a system containing 200 μg/L Al, the emergence of phosphate's effect on Pb control was delayed, and the dissolved Pb concentration decreased but stabilized at a higher value (10-12 μg/L) than in the Al-free system. Phosphohedyphane (Ca2Pb3(PO4)3Cl) was formed in all phosphate-containing systems, and PbO2 was formed independent of phosphate addition. The effect of Al on Pb release was probably related to its influence on the composition and morphology of Pb-containing minerals on coupon surfaces. The laboratory study has unavoidable limitations in its ability to simulate all conditions in real lead service lines, but this study still highlights the importance of considering the influence of Al when designing Pb corrosion control strategies.

Formation of ultrathin segregated-Ge crystal on Al/Ge(111) surface

We have investigated the formation of an ultrathin Ge crystal layer by vacuum annealing of the Al/Ge(111) structure. An hetero-epitaxial Al layer was found to be grown on a Ge(111) substrate by control of Al thickness and deposition rate during thermal evaporation, which the Al surface becomes the template of crystallographic structure of a segregated Ge layer. Then, surface flattening and Ge segregation of the Al/Ge(111) structure by vacuum annealing were evaluated, and the formation of ultrathin segregated-Ge crystals with a thickness below 1 nm on the hetero-epitaxial Al surface have been demonstrated.

Process-dependent effects of water on the chemistry of aluminum oxide and aromatic polyimide interface in composite materials

Replacement of Cu wires with Al wires has a significant impact on the overall cable and wire fields. This replacement is particularly important for reducing the weight of hybrid vehicles, significantly improving fuel efficiency, and reducing CO2 emissions. A promising analytical protocol is proposed for investigating the Al and polymer coating interface in samples fabricated by semiconductor-device-manufacturing techniques. The samples were analyzed by time-of-flight secondary ion spectrometry (TOF-SIMS), synchrotron hard-X-ray photoelectron spectroscopy (HAXPES), and electron energy loss spectroscopy with scanning transmission electron microscopy (STEM-EELS). The protocol provides information about the chemistry of interfaces fabricated by (1) Al deposition on a polymer substrate and (2) coating of a polymer precursor on Al. Observation of the Al and pyromellitic-dianhydride-oxydianiline-type polyimide (PMDA-ODA PI) interfaces revealed: For (1), the water adsorbed on the pristine PI surface contributed mainly to formation of the Al hydrate. For (2), at the Al/PI interface, the two events occur in a chain: first, hydrolysis of PAA occurred to form the carboxyl group, followed by acid-base reactions between the carboxyl group and hydroxide/oxide to generate water. Thus, AlOCO bonds form at the interface. The proposed protocol is applicable to the investigation of a wide-ranging combination of metals and polymers.

Room-Temperature Electrodeposition of Aluminum via Manipulating Coordination Structure in AlCl3 Solutions.

The coordination mechanism of chloroaluminate species in aluminum chloride (AlCl3) solutions in γ-butyrolactone (GBL) is investigated using electrochemical, spectroscopic, and computational methods. The liquid-state 27Al NMR spectroscopy shows a sequence of new species generated in the AlCl3-GBL solutions with increasing AlCl3/GBL ratio. Ab initio molecular dynamics simulation reveals the dynamic coordination process between GBL and AlCl3, and the resultant chloroaluminate species are identified as [AlCl2·(GBL)2]+, AlCl4-, AlCl3·GBL, and Al3Cl10-. The species are further confirmed by surface enhanced Raman spectroscopy combined with calculated Raman spectra from methods based on density functional theory. Electrochemical deposition of Al is achieved from the AlCl3-GBL solution containing Al3Cl10-, which is one of the few noneutectic electrolytes for room-temperature Al deposition reported to date.

Electrochemical Deposition of Al-Ti Alloys from Equimolar AlCl3 + NaCl Containing Electrochemically Dissolved Titanium

Al-Ti alloys were electrodeposited from equimolar chloroaluminate molten salts containing up to 0.1 M of titanium ions, which were added to the electrolyte by potentiostatic dissolution of metallic Ti. Titanium dissolution and titanium and aluminium deposition were investigated by linear sweep voltammetry and chronoamperometry at 200 and 300 °C. Working electrodes used were titanium and glassy carbon. The voltammograms on Ti obtained in the electrolyte without added Ti ions indicated titanium deposition and dissolution proceeding in three reversible steps: Ti4+ ⇄ Ti3+, Ti3+ ⇄ Ti2+ and Ti2+ ⇄ Ti. The voltammograms recorded with glassy carbon in the electrolyte containing added titanium ions did not always clearly register all of the three processes. However, peak currents, which were characteristics of Al, Ti and Al-Ti alloy deposition and dissolution, were evident in voltammograms on both working electrodes used. A constant potential electrodeposition regime was used to obtain deposits on the glassy carbon working electrode. The obtained deposits were characterized by SEM, energy-dispersive spectrometry and XRD. In the deposits on the glassy carbon electrode, the analysis identified an Al and AlTi3 alloy formed at 200 °C and an Al2Ti and Al3Ti alloy obtained at 300 °C.

Inorganic AlCl3-alkali metal thiocyanate ionic liquids as electrolytes for electrochemical Al technologies.

A series of inorganic AlCl3-alkali metal thiocyanate (AMSCN: AM = Li, Na, K) ionic liquids (ILs) are demonstrated as electrolytes for Al electrodeposition and Al-anion rechargeable batteries (AARBs) at 303-363 K. Al deposits with a unique flake nanostructure are obtained in these electrolytes. The assembled AARBs show a stable cyclability over 250 cycles with a reversible capacity of ca. 70 mA h (g-graphite)-1 at 363 K. These inorganic ILs inherit the advantages of conventional chloroaluminate ILs (applicability at near-ambient temperature) and molten salts (cost effectiveness), making them promising electrolyte candidates for industrializable electrochemical Al technologies.

Retrospective clinical and morphological analysis of patients with AL amyloidosis (the 2008 to 2015 nephrobiopsies)

To study correlations between the clinical signs of dysfunction and pathological structural changes in the renal parenchyma in a group of Russian patients with AL amyloidosis in 2008-2015. A total group (At) including Group 1 with AL (kappa + lambda light chains) (n=46) was divided into subgroups: 2λ) 40 patients with AL-lambda (AL-λ); 3κ) 6 patients with AL-kappa (AL-κ). All the patients underwent standard laboratory and instrumental studies: determinations of the peak systolic and diastolic blood pressures (SBP and DBP, respectively, mm Hg), glomerular filtration rate (GFR) (ml/min/1.73 m2) by the EPI equation, daily protein loss (g/day). Polyclonal antibodies against kappa and lambda light chains, AA component, and transthyretin (DAKO, Denmark) were used as immunomorphological markers. Light optical structural changes were semiquantitatively assessed, by ranking the following analyzed sign: interstitial focal sclerosis (FS), tubular atrophy (TA), interstitial inflammatory infiltration (II) semi-quantitatively (0 - no; 1 - < 25%; 2 - <50%, 3 - >50% of the volume of a histological compartment). Glomerulosclerosis (GS) was defined as the percentage of sclerotic glomeruli. The extent of amyloid depositions in the renal parenchyma structures was estimated according to the procedure proposed by Ying Yao et al., 2013. The AL group showed a female preponderance (65.21%). The patients' mean age was 62±11 years. There were no significant differences in daily proteinuria and the levels of serum creatinine, GFR, SBP, and DBP between the groups. The predominant clinical manifestation in the patients was nephrotic syndrome. A comparative analysis of the pathomorphological criteria for the spread of amyloid masses and the markers of fibroplastic processes revealed no statistically significant differences in the studied groups. Correlation analysis of the spread of AL deposits in the renal parenchyma in the patients of Group 1 and Subgroup 2λ, as well as laboratory data showed that there were significant (p<0.05) correlations with GFR, serum creatinine, unlike in Subgroup 3κ. At the same time, the analysis demonstrated that daily proteinuria had a significant positive correlation with VA, IA, GA, and TA values in Subgroup 3κ, unlike in Group 1 and Subgroup 2λ. Positive correlations were found between glomerulosclerosis and VA in Subgroup 2 λ and IA in Group 1. Sclerotic (FS and TA) changes in the tubular interstitium (TIN) were significantly positively correlated with all the indicators of AL (GA, VA, IA, TA) in the examinees in Group 1 and Subgroup 2λ, but not in Subgroup 3κ. Inflammatory TIN infiltration showed statistically significant (p<0.05) positive correlations with IA and VA in Group 1 and Subgroup 2λ and their absence in subgroup 3κ. : The retrospective analysis of nephrobiopsy specimens from of patients with AL amyloidosis revealed that kidney damage was mainly associated with the development of λ-associated AL amyloidosis. The clinical and laboratory parameters were correlated with the pathomorphological criteria for loading the renal parenchyma with amyloid masses. The findings suggest that there are clinical and morphological features of the subclasses of AL amyloidosis, which may be of value for predicting the course and progression of the disease.

A micro optofluidic system for toluene detection application

A new application of metal deposited poly (methyl methacrylate) (PMMA) microchannel for optical detection of toluene in the UV spectrum region is presented in this study. Laser cutting and hole formation in initial PMMA sheets, micro-milling for groove shaping, aluminium deposition on two caps using DC magnetron sputtering for increasing optical path length, and bonding process using thermally-solvent method are the main steps for the microchannel fabrication. The dimensions and length of microchannel are 370 μm × 370 μm and 5 cm, respectively. The SEM and leakage tests are implemented to investigate the quality of the microchannel. Besides, the characterization results indicate that Al deposition has no adverse influence on the bonding process. Our simulation results indicate that the optical path length enhanced by 2.2% and the loss decreased by 48.9% when Al is deposited on the surfaces of the microchannel. Also, the effect of microchannel length on optical path length and loss is investigated using simulation. The optical detection tests are performed in a single step using UV spectroscopy based on absorption for toluene in concentration range within 20–800 ppm. The tests are repeated several times for each toluene concentration. Our experimental observation indicate that the results obtained from this optofluidic system is repeatable with linear gas detection and fast response and perfect selectivity which make it a good candidate for toluene detection applications.

Quantitative [18F]florbetapir PET/CT may identify lung involvement in patients with systemic AL amyloidosis.

The clinical diagnosis of pulmonary involvement in individuals with systemic AL amyloidosis remains challenging. [18F]florbetapir imaging has previously identified AL amyloid deposits in the heart and extra-cardiac organs. The aim of this study is to determine quantitative [18F]florbetapir pulmonary kinetics to identify pulmonary involvement in individuals with systemic AL amyloidosis. We prospectively enrolled 58 subjects with biopsy-proven AL amyloidosis and 9 control subjects (5 without amyloidosis and 4 with ATTR cardiac amyloidosis). Pulmonary [18F]florbetapir uptake was evaluated visually and quantified as distribution volume of specific binding (Vs) derived from compartmental analysis and simpler semiquantitative metrics of maximum standardized uptake values (SUVmax), retention index (RI), and target-to-blood ratio (TBR). On visual analysis, pulmonary tracer uptake was absent in most AL subjects (40/58, 69%); 12% (7/58) of AL subjects demonstrated intense bilateral homogeneous tracer uptake. In this group, compared to the control group, Vs (median Vs 30-fold higher, 9.79 vs. 0.26, p < 0.001), TBR (median TBR 12.0 vs. 1.71, p < 0.001), and RI (median RI 0.310 vs. 0.033, p < 0.001) were substantially higher. Notably, the AL group without visually apparent pulmonary [18F]florbetapir uptake also demonstrated a > 3-fold higher Vs compared to the control group (median 0.99 vs. 0.26, p < 0.001). Vs was independently related to left ventricular SUVmax, a marker of cardiac AL deposition, but not to ejection fraction, a marker of cardiac dysfunction. Also, intense [18F]florbetapir lung uptake was not related to [11C]acetate lung uptake, suggesting that intense [18F]florbetapir lung uptake represents AL amyloidosis rather than heart failure. [18F]florbetapir PET/CT offers the potential to noninvasively identify pulmonary AL amyloidosis, and its clinical relevance warrants further study.

Role of salicylic acid in alleviating the inhibition of root elongation by suppressing ethylene emission in rice under Al toxicity conditions

Salicylic acid (SA) is the phytohormone responsible for the regulation of growth and response to environmental stress in plants. In the present study, the application of 1 μM SA significantly enhanced the SA content in rice roots and improved their growth when affected by Al toxicity by concomitantly decreasing the Al content of the root apex. The addition of SA significantly inhibited the synthesis of pectin and hemicellulose, suppressed the activity of pectin methylesterase (PME), and decreased the cell wall Al content. The expression of OsSTAR1 (sensitive to Al rhizotoxicity) and OsSTAR2 was induced by SA to mask the Al-binding sites in the cell walls. The expression of OsALS1 (Al sensitive) was also stimulated by SA, which improved the transport of cytoplasmic Al into the vacuoles. In rice affected by Al toxicity, SA significantly increased the activity of catalase and peroxidase and reduced the H2O2 content and malondialdehyde content. The expression of OsACS1 (ACC synthase) and OsACO1 (ACC oxidase) was inhibited by SA and thus inhibited ethylene emission. The addition of ethylene precursor 1-aminocylopropane-1-carboxylic acid (ACC) along with SA under Al toxicity conditions aggravated the inhibition of root elongation, accompanied by an increased Al content in the root apex and cell walls, increased pectin content, and rendered PME activity greater than with single Al treatment. However, the addition of aminoethoxyvinylglycine (AVG, inhibitor of the ACC synthase) along with SA under Al toxicity conditions showed the opposite effect, indicating that SA inhibited ethylene emission, thus reducing the Al deposition on cell walls.

Detection of aluminum in lumbar spinal cord of sheep subcutaneously inoculated with aluminum-hydroxide containing products

The use of vaccines containing aluminum (Al) adjuvants is widespread in ovine production. Al adjuvants induce an effective immune-response but lead to the formation of post-vaccination granulomas from which Al can disseminate. This work aims to study the accumulation of Al in the central nervous system of sheep subcutaneously inoculated with Al-hydroxide containing products. Lumbar spinal cord and parietal lobe from 21 animals inoculated with 19 doses of Vaccine (n = 7), Adjuvant-only (n = 7) or phosphate-buffered saline as Control (n = 7) were analyzed with transversely heated graphite furnace atomic absorption spectroscopy and lumogallion staining for Al analytical measurements and Al tisular localization respectively. In the lumbar spinal cord, Al median content was higher in both the Adjuvant-only and Vaccine group (p = .001) compared with the Control group. Animals of the Adjuvant-only group showed the higher individual measurements in the lumbar spinal cord (14.36 μg/g and 7.83 μg/g). In the parietal lobe, Al median content tended to be higher in the Adjuvant-only group compared with Control group (p = .074). Except for three replicates of the Adjuvant-only group, Al content was always below 1 μg/g. In the lumbar spinal cord, lumogallion-reactive Al deposits were more abundant in the gray matter than in the white matter in both Vaccine (p = .034) and Adjuvant-only groups (p = .017) and Al deposits were mostly associated with glial-like cells (p = .042). In the parietal lobe, few Al deposits, which were sometimes related to blood vessels, were found. In sheep, Al-hydroxide adjuvants inoculated in the subcutaneous tissue selectively accumulate in the lumbar spinal cord.

Depositing Al-Based Metallic Coatings onto Polymer Substrates by Cold Spray

The feasibility of depositing aluminum onto thermoplastic substrates via cold spray (CS) was investigated. Dense coatings of 7075 Al and CP Al (commercial purity) were achieved on three substrates—polyetheretherketone (PEEK), polyetherimide (PEI), and acrylonitrile butadiene styrene (ABS) using an iterative optimization process. 7075 Al deposition yielded low deposition efficiencies (DEs) and low thicknesses but high adhesive strengths, while CP Al deposition led to high DEs and thicknesses but relatively low adhesive strengths. PEEK and PEI were more suitable substrates for cold spray than ABS, which suffered from surface erosion and substrate distortion. Two key factors were identified that influenced the DE and adhesive strength of the coating. The first factor was the bond layer, the initial few particle layers that fused with the substrate to allow subsequent buildup. The bond layer was influenced by the substrate hardness, yield strength, glass transition temperature, and impact strength, as well as the differences in thermal expansion coefficients of Al and the polymer substrates. The second factor was the CS process parameters selected, as the bond layer and the build-up layers may require different process conditions in order to optimize both bonding strength and coating strength, respectively.

Adherent Light-Induced Al Plating on Si for Substitution of Ag in Si Solar Cells

Silver (Ag) is one of the most expensive materials used in the manufacture of silicon (Si) solar cells today as the front electrode. The current Si cell manufacturing cost from Si wafers is ~$0.10 per cell and Ag accounts for about half of that cost. Another key issue is the limited reserve of Ag on our planet, with a US Geological Survey estimated amount of 530,000 metric tons [1]. Even if the entire Ag reserve was used for cell manufacturing, we could only supply ~5% of the 2100 global energy demand [2]. Based on material cost, abundance, and resistivity, only two suitable replacements for Ag exist, Cu and Al. Al bears the advantage over Cu since it eliminates the need for a barrier layer such as Ni. Al is also less prone to oxidization often experienced by Cu. We reported light-induced Al electroplating on Si solar cells using a Lewis acidic chloroaluminate ionic liquid [3], demonstrating direct Al plating on Si without a seed layer. This talk focuses on surface preparation and Al plating processes to promote strong adhesion and low contact resistance between plated Al and cell emitter. Sheet resistance and surface morphology of the emitter were monitored as a function of laser power for SiNx removal. Electrochemical capacitance-voltage profiling determined the laser power at which the emitter surface dopant profiles were preserved. A process to remove laser damage and clean the Si surface after laser patterning was developed by etching Si in 1 wt% NaOH. It was found by atomic force microscopy that ~23 s was the minimum time to completely remove the original Si surface which was damaged and contaminated. Al deposits on substrates prepared by this surface cleaning process showed strong adherence in the Scotch tape test. Al plating was performed at different temperatures. The resulting film thickness and morphology were investigated with scanning electron microscopy. The lowest film resistivity was less than 8 µΩ-cm which was obtained at a plating temperature of 50°C and showed a grain size of 2–5 µm. [1] U.S. Geological Survey, Mineral Commodity Summaries (2017). [2] M. Tao, Terawatt Solar Photovoltaics: Roadblocks and Opportunities (Springer, London, 2014). [3] L. Wang, W.-H. Huang, W. J. Shin, M. Tao, B. Deng, and D. Wang, J. Electrochem. Soc., 165, D381 (2018).

Throwing Power in Chloroaluminate Ionic Liquids: Effects of Metal Concentration, Additives and Waveform on Aluminum/Aluminum Alloy Deposition on Complex Geometries

Al deposition from chloroaluminate ionic liquids necessitates the use of consumable anodes and near 100% plating efficiency in order prevent irreversible breakdown of the electrolyte. A significant side effect of this high plating efficiency is poor deposit thickness uniformity across current density gradients. For simple or axisymmetric geometries under ideal plating conditions it is straight forward to mitigate such issues through traditional thieving or shielding. However, as part geometries become more complex, and plating conditions less ideal (i.e. barrel plating of small parts), methods of improving poor throwing power resulting from secondary current density effects become less obvious. Addressing this issue is critical in enabling Al plating technologies to progress commercially. We have explored the effects of metal concentration, additives and plating waveform on deposit thickness uniformity for rack and barrel plated parts of increasing geometric complexity in order to minimize plating thickness distribution and improve throwing power of [AlCl3:EMIMCl] chloroaluminate electrolytes into high aspect ratio features.

Low-Power, High-Sensitivity Temperature Sensor Based on Ultrathin SOI Lateral p-i-n Gated Diode

In this work, we present a silicon-based p-i-n thermal diode, with post-CMOS MEMS processing (deep reactive ion etching and Al deposition) and annealing (at 250 °C). The MEMS processing degraded device stability as well as thermal sensing linearity and sensitivity, while the local annealing recovered the device performance (forward and reverse characteristics) by reducing the trap density and improving the carrier lifetime. After annealing, the on-membrane diode can achieve stabilized thermal linearity with a high sensitivity of ~ 2.25 mV/°C at 0.02– $0.03~\mu \text{A}$ low constant current, in the temperature range from room temperature to 200 °C, under a back-gate bias of 90 V to achieve a fully-depleted condition in the intrinsic (I) region and decrease the trap-assisted recombination at the front surface which dominates and degrades the device forward output current. To be compatible with commercial 1.0- $\mu \text{m}$ SOI CMOS technology, a front gate with a 25-nm-thick oxide dielectric is proposed and simulated in Atlas/SILVACO to optimize the device performance and achieve the same thermal characteristics under a front-gate bias of 1.0 V, showing its potential in low-power consumption electronics. The temperature sensor investigated in this work shows its industrial capability in gas sensing and integrated circuit applications.

Electrodeposition of Aluminum Nanoplatelet from AlCl3–1-Ethyl-3-Methylimidazolium Chloride–Urea Mixtures

Aluminum electrodeposition is generally conducted in nonaqueous solvents because of its negative electrode potential (-1.66 V (vs. NHE)). Among the solvents, Lewis acidic chloroaluminate ionic liquids (ILs) and deep eutectic solvents (DESs), which contain AlCl3 over 50 mol% and are handled at room temperature, are commonly employed for the electrodeposition process. Recently, these solvents are also expected as the electrolyte for Al-anion secondary battery.1 A great number of articles on Al technologies using AlCl3–1-ethyl-3-methylimidazolium chloride ([C2mim]Cl) IL2 and AlCl3–urea DES3 have been reported so far. However, there is no report on Al electrodeposition from the Lewis acidic chloroaluminate ternary mixtures consisting of AlCl3, [C2mim]Cl, and urea. In this study, we examine the electrochemical behavior of Al deposition process and the association between the morphology variations in the Al electrodeposits and electrodeposition conditions. The procedures used for the preparation and purification of the AlCl3, [C2mim]Cl, and urea, were identical with those described in previous articles.2,3 The molar fraction of AlCl3 in each mixture was 60 mol%. The sum of molar fraction for the [C2mim]Cl and urea was 40 mol%. Their molar fraction was changed in the range of 0 ~ 40 mol%. The electroanalytical measurements were conducted using a three-electrode cell. The working electrode was a Pt disk electrode. An Al plate was used for the counter electrode. The reference electrode was an Al wire immersed directly in the electrolyte. Galvanostatic electrodeposition was conducted using Cu plate electrodes. All the experiments were carried out in an Ar gas-filled glove box with O2 and H2O < 1 ppm. The resulting Al samples were characterized by SEM, EDX, and XRD. Operando digital microscope observation for the Al electrodeposition process was performed by using the specially designed two-electrode airtight electrochemical cell. Figure 1 shows SEM images of the pure Al electrodeposits prepared in 60.0-40.0 mol% AlCl3–[C2mim]Cl IL and 60.0-40.0 mol% AlCl3–urea DES under the same electrodeposition conditions. EDX analysis of the electrodeposits revealed that they are pure Al without chloride contamination. When the IL electrolyte was used, the Cu substrate surface was covered with dense crystals. Meanwhile, in the case of the DES electrolyte, surprisingly Al nanoplatelets having very smooth surface were yielded at 333 K but not 293 K, when the applied current density was -5 ~ -20 mA cm-2. The Al nanoplatelets were readily obtained at the bath temperature over 313 K. The surface morphology of the electrodeposit obtained at 293 K was similar to that shown in Fig. 1a. XRD patterns of the Al deposits revealed that specimens shown in Fig. 1a and 1b were Al polycrystalline Al and (111)-preferentially oriented Al, respectively (Fig. 2a and 2e). The unexpected electrodeposition behavior recognized in the DES solvent has not been observed in the chloroaluminate IL. In order to get further insights concerning the interesting behavior, the electrodeposition was conducted in the ternary AlCl3–[C2mim]Cl–urea mixtures under the same condition that can produce Al nanoplatelet in the AlCl3–urea DES. Here we used three types of mixtures, 60.0-30.0-10.0 mol%, 60.0-20.0-20.0 mol%, and 60.0-10.0-30.0 mol% AlCl3–[C2mim]Cl–urea. As we expected, the increase in the urea molar faction in the ternary mixture caused the variation in the surface morphology. The nanoplatelet structure appeared in only the 60.0-10.0-30.0 mol% AlCl3–[C2mim]Cl–urea. It suggests that the urea contributes the formation of unique platelet structure. Because direct observation of the electrodeposition process enables to propose the plausible formation mechanism, airtight electrochemical cell for the operando digital microscope was newly designed. From the video clip during the electrodeposition process, two-dimensional crystal growth of the Al deposits was visually recognized in the 60.0-40.0 mol% AlCl3–urea DES. The detailed information obtained from the operando observation including the video clip will be given in our presentation. References T. Tsuda, G. R. Stafford, and C. L. Hussey, J. Electrochem. Soc., 164, H5007 (2017) and references therein.J. S.Wilkes, J. A. Levisky, R. A.Wilson, and C. L. Hussey, Inorg. Chem., 21, 1263 (1982).H. M. A. Abood, A. P. Abbott, A. D. Ballantyne, and K. S. Ryder, Chem. Commun., 47, 3523 (2011). Figure 1