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Among the structures using for fabricating white light-emitting diodes (WLEDs) such as the conformal coating or in-cup geometries, the remote phosphor structure gives the highest luminous efficacy. However, in terms of color quality, its performance is not as good as the others. The red-light compensation has been reported as the effective solution for enhancing the color quality of WLEDs. Hence, this study adopted the idea and applied to the dual-layer phosphor structure. The phosphor used to boost the red color in light formation is (Y,Gd)BO3:Eu particle. The dual-layer remote phosphor structure was simulated with the red (Y,Gd)BO3:Eu phosphor layer above the original yellow phosphor YAG:Ce3+ one. The WLEDs with different correlated color temperatures of 5600 K, 6600 K and 7700K were experimented. Mie-theory and Lambert-Beer law were applied to examine the results. The growth in color rendering index (CRI) and color quality scale (CQS) with the increase of (Y,Gd)BO3:Eu phosphor concentration was observed. Nevertheless, the lumen efficacy would be degraded if the concentration was over a certain number. The information provided in this article is useful for the development of high-power WLED production with greater color quality.

This work presents the development and characterization of a Silicon based MEMS vibrating mesh atomizer for use in Spin-spray deposition of low viscosity liquids. The device design, fabrication process, and application of MEMS atomizer for spin-spray method is discussed. The new spin-spray atomizer is demonstrated using spin on glass and Su-8 photoresist. Spin on glass was used to create a SiO2 layer on silicon substrates with the above-mentioned method. The experimental study compares the new spin-spray method with conventional spin coating based on uniformity, 3D-topography coating, etch rate, film stress, and surface roughness. Low viscosity SU-8 was used to further validate the concept of using the vibrating mesh device to pattern planar and 3D topographical structures. The results demonstrate increased uniformity and less wasted chemicals using spin-spray compared to spin coating deposition. The new vibrating mesh device is smaller, has enhanced droplet size control, easy to integrate into a standard spin coater, and uses less power than traditional ultrasonic spin-spray deposition methods. In addition, the new spin-spray method demonstrated increased conformal coating of 3D microstructures of $> 40~\mu \text{m}$ thick structures compared to standard spin coating. [2021-0040]

Li metal anode holds great promise to realize high-energy battery systems. However, the uncontrollable Li dendrites formation and infinite volume changes of Li severely hinder its practical applications. Herein, a 3D conductive carbon fibre with conformal lithiophilic Zn coating (CF@Zn) is developed to guide uniform Li plating/stripping and accommodate a large amount of Li metal. Phase evolution mechanism reveals that lithiated zinc (LiZn) alloy plays the real role in regulating the Li plating. Through the conformal incorporation of LiZn alloy, the Li affinity of carbon fibre has been improved significantly, which reduces the Li nucleation barrier and enables homogeneous Li nucleation and growth surround the carbon fibre, forming a conformal CF@LiZn@Li structure at initial stage. The 3D lithiophilic CF@LiZn scaffold with interconnected pores serves as robust host for high Li loading with small volume fluctuation, resulting in a dendrite-free Li metal battery with high areal capacity (up to 12 mAh cm−2). Moreover, the CF@LiZn electrode exhibits a high Coulombic efficiency of 97.1% at 5 mA cm−2, long cycle life of 280 cycles at 2 mA cm−2 and excellent rate performance (∼70 mV voltage hysteresis at 5 mA cm−2). Furthermore, excellent cyclability and rate performance are realized in full-cell batteries with CF@LiZn–Li anode and LiFePO4 cathode. This work demonstrates a low-cost and lithiophilic alloy matrix for the fabrication of stable Li metal anode toward next-generation high-energy battery systems.

Elektronska oziroma opremljena tiskana vezja so v avtomobilskih aplikacijah, tekom delovanja izpostavljena številnim agresivnim okolijskim dejavnikom, kot so vlaga, visoka in nizka temperatura, mehanska obraba ipd., zaradi katerih je vezje še tako bolj občutljivo za korozijo vezanih komponent. V ta namen je na površino elektronskega vezja nanešen konformni premaz, ki služi kot primaren sloj zaščite pred omenjenimi dejavniki. Pred nanosom konformnega premaza je treba površino očistiti in aktivirati ter s tem zagotoviti optimalno omočljivost in adhezijo. Poznamo več postopkov predobdelave površin, med katere spada tudi uporaba odprto-zračnega plazemskega procesa čiščenja in aktivacije. Cilj diplomskega dela je bil pregledati literaturo uporabe plazme ter na podlagi eksperimentov optimizirati proces čiščenja in aktivacije površine elektronskega vezja z odprto-zračno plazemsko tehnologijo. Raziskave so vključevale še kvantitativne meritve čistosti in omočljivosti površine ter meritve adhezije konformnega premaza na plazemsko obdelani in neobdelani površini s »cross-cut« testom. Rezultati so pokazali, da je površina elektronskega vezja po obdelavi s plazmo znatno bolj omočljiva, adhezija nanešenega premaza pa tudi precej boljša. In automotive applications, printed circuit board assemblies are exposed to many aggressive environmental factors, such as moisture, high and low temperatures, mechanical stress, etc., which make the circuit even more sensitive to corrosion of electronic components. For this purpose, a conformal coating is applied to the surface of the printed circuit board assembly, which serves as a primary layer of protection against the aforementioned factors. Before applying the conformal coating, the surface must be cleaned and activated, thereby ensuring optimal wettability and adhesion. There are several surface pre-treatment processes, including the use of open-air plasma. The aim of this diploma thesis was to review the literature on the use of plasma and based on experiments, optimize the process of surface cleaning and activation with open-air plasma technology. The research also included quantitative measurements of the cleanliness and wettability of the surface, as well as measurements of the adhesion of the conformal coating on the plasma-treated and untreated surface with a "cross-cut" test. The results indicated that the plasma treated surface is significantly more wettable and the adhesion of the applied coating is superior.

The synthesis of uniform low-defect graphene on a catalytic metal substrate is getting closer to the industrial level. However, its practical application is still challenging due to the lack of an appropriate method for its scalable damage-free transfer to a device substrate. Here, an efficient approach for a defect-free, etchant-free, wrinkle-free, and large-area graphene transfer is demonstrated by exploiting a multifunctional viscoelastic polymer gel as a simultaneous shock-free adhesive and dopant layer. Initially, an amine-rich polymer solution in its liquid form allows for conformal coating on a graphene layer grown on a Cu substrate. The subsequent thermally cured soft gel enables the shock-free and wrinkle-free direct mechanical exfoliation of graphene from a substrate due to its strong charge-transfer interaction with graphene and excellent shock absorption. The adhesive gel with a high optical transparency works as an electron doping layer toward graphene, which exhibits significantly reduced sheet resistances without optical transmittance loss. Lastly, the transferred graphene layer shows high mechanical and chemical stabilities under the repeated bending test and exposure to various solvents. This gel-assisted mechanical transfer method can be a solution to connect the missing part between large-scale graphene synthesis and next-generation electronics and optoelectronic applications.

Engineering the nucleation and growth of plasmonic metals (Ag and Au) on their pre-existing seeds is expected to produce nanostructures with unconventional morphologies and plasmonic properties that may find unique applications in sensing, catalysis, and broadband energy harvesting. Typical seed-mediated growth processes take advantage of the perfect lattice match between the deposited metal and seeds to induce conformal coating, leading to either simple size increases (e.g., Au on Au) or the formation of core-shell structures (e.g., Ag on Au) with limited morphology change. In this work, we show that the introduction of a thin layer of metal with considerable lattice mismatch can effectively induce the nucleation of well-defined Au islands on Au nanocrystal seeds. By controlling the interfacial energy between the seed and the deposited material, the oxidative ripening, and the surface diffusion of metal precursors, we can regulate the number of islands on the seeds and produce complex Au nanostructures with morphologies tunable from core-satellites to tetramers, trimers, and dimers. This surface engineering strategy is of great significance in nanomaterial synthesis as it is general and can be used to create secondary structures of many other nanocrystals in a controllable manner.

To improve the performance of Flash LED for obtaining good picture quality, a novel ceramic packaging structure was designed and optimized based on illuminance homogeneity and angular color uniformity (ACU) for meeting the requirement of mobile flash products. The illuminance homogeneity was analyzed via both near-field optical measurement and optical simulation by Monte-Carlo method according to nine dots measurement method. Their results matched well. The target package includes vertical chip, Al2O3 substrate, phosphor conformal coating layer, and silicone molding as encapsulation. Through the layer print approach and layer transfer method, the thickness of phosphors layer was optimized by finite element analysis method to improve the temperature distribution and eventually the reliability of LED units. In addition, good Delta CCT was obtained by optimizing the phosphor layer. The design methods were characterized by electrical-optical testing.

For application in harsh environmental conditions, printed circuit boards (PCB) are usually coated with a protective polymer typically of a 50-µm thickness that provides electrical insulation.

Nanoporous SnO2@TiO2 heterostructure was synthesized by a facile two-step dry process, modified thermal evaporation followed by atomic layer deposition (ALD). The introduction of inert gas, Ar, with a pressure of 0.2 Torr during thermal evaporation of SnO, enabled the formation of the nanoporous 3D structure by inducing the collision and loss of kinetic energy during deposition. A photocatalytic material, TiO2, was grown on the porous structure of SnO2 to detect target gas, formaldehyde, under UV irradiation selectively. Microstructural and elemental analysis with a transmission electron microscope and X-ray photoelectron spectroscopy confirmed the porous structure of SnO2 induced by our evaporation process as well as the conformal coating of TiO2 on the porous structure. The sensing capabilities of a photoactive sensor on the formaldehyde were assessed in terms of the film porosity, irradiated UV power, and thickness of photoactive materials at room temperature. As a result, the SnO2@TiO2 heterostructure, with an optimum thickness of TiO2 exhibited low detection limit, down to 0.1 ppm, good linearity to the concentration of formaldehyde in the range of 0.1???10 ppm, and high response of 15% in the HCHO 0.1 ppm. This core-shell porous structure developed by modified thermal evaporation combined with ALD paved the way for 3D architectures to explore various applications, such as biosensors, photocatalysts, and optoelectronic devices.

We report on the conformal coating of thickness-tunable multilayers directly onto the sulfur (S8) cathodes by the layer-by-layer (LbL) deposition for the significant improvement in the performances of Li–S batteries even without key additives (LiNO3) in the electrolyte. Poly(ethylene oxide) (PEO)/poly(acrylic acid) (PAA) multilayers on a single poly(allylamine hydrochloride) (PAH)/PAA priming bilayer, deposited on the S8 cathodes, effectively protected from the polysulfide leakage, while providing a Li+ ion diffusion channel. As a result, PAH/PAA/(PEO/PAA)3 multilayer-coated cathodes exhibited the highest capacity retention (806 mAh g–1) after 100 cycles at 0.5 C, as well as the high C-rate capability up to 2.0 C. Furthermore, the multilayer coating effectively mitigated the polysulfide shuttle effect in the absent of LiNO3 additives in the electrolyte.

Conventional templating synthesis confines the growth of seeds in rigid spaces to achieve faithful morphological replication. Herein, we explore the use of spherical shape-deformable polymeric nanoshells to regulate the anisotropic growth of Ag nanoplates. The flexible shells deform adaptively to accommodate the initial overgrowth of the seeds but restrict the growth in the directions where the shells are fully stretched, eventually producing nanoplates with an unconventional circular profile. The diameter of the final Ag nanoplates can be precisely predicted by stretching and flattering the nanoshells into a plate-like capsule while retaining their original internal surface area. Furthermore, unlike conventional templates, the polymer shells eventually turn themselves into a conformal coating that binds to the surface of the full-grown Ag nanoplates and significantly enhances their stability against oxidative etching.

Lithium (Li) metal is regarded as a “Holy Grail” anode for next-generation rechargeable batteries due to its ultrahigh theoretical specific capacity and extremely low redox potential. Lithium metal batteries (LMBs) with high energy density have received extensive research attentions and been considered to be one of the most promising candidates for the post lithium-ion battery era. However, the intrinsic properties of Li metal hinder the practical application of LMBs, including severe safety concern and poor cycling stability. The closely related problems include: (1) The growth of Li dendrites to penetrate the polymer separator and cause a short circuit of cell; (2) the infinite volume expansion and contraction during Li plating and stripping processes to cause the continuous exposure of fresh Li and consumption of electrolyte; (3) the accumulation of electrochemically inert dead Li so as to increase the cell impedance and decease the Coulombic efficiency. Therefore, it is essential to address the above issues in order to achieve the safe and stable Li metal anode. In the past years, some models about the growth of Li dendrites have been proposed, and they can help us understand the dendrite growth mechanisms and guide the direction toward the design of prospective anodes. And some strategies such as anode structural design, solid-state electrolyte, separator decoration, artificial solid-state electrolyte interphase (SEI), additives and so on have been demonstrated to enable an effective suppression or alleviation of the growth of Li dendrites. Herein, we highlight the strategies of functional additives and conformal coating, especially their impacts on the composition and structure of the electrode/electrolyte interface, and thus on the homogenization of the Li-ion flux and formation of the uniform deposition of Li. Small amounts of additives can react with Li to regulate the properties of SEI, or disperse in the electrolyte as an ion transport channel to modulate the distribution of Li-ion flux. The construction of a conformal coating with rich lithiophilic sites on the Li metal anode or current collector can also tailor the Li ion plating behavior, and the binding energy between lithiophilic groups and Li atoms is obtained through calculation to prove the role of lithiophilic sites. In addition, conformal coating of Li metal can also improve its air stability, which is beneficial to the future commercial application of LMBs. Furthermore, the fluorine-rich components and robust inorganic moieties that may be formed based on both the above strategies are discussed, so as to obtain reinforced SEI with low resistance. We aim to illustrate the design ideas based on the recent works in this field and provide inspiration for the future research on Li metal anode.

Atomic layer deposition (ALD) derived ultrathin conformal Al2O3 coating has been identified as an effective strategy for enhancing the electrochemical performance of Ni-rich LiNixCoyMnzO2 (NCM; 0 ≤ x, y, z < 1) based cathode active materials (CAM) in Li-ion batteries. However, there is still a need to better understand the beneficial effect of ALD derived surface coatings on the performance of NCM based composite cathodes. In this work, we applied and optimized a low-temperature ALD derived Al2O3 coating on a series of Ni-rich NCM-based (NCM622, NCM71.51.5 and NCM811) ready-to-use composite cathodes and investigated the effect of coating on the surface conductivity of the electrode as well as its electrochemical performance. A highly uniform and conformal coating was successfully achieved on all three different cathode compositions under the same ALD deposition conditions. All the coated cathodes were found to exhibit an improved electrochemical performance during long-term cycling under moderate cycling conditions. The improvement in the electrochemical performance after Al2O3 coating is attributed to the suppression of parasitic side reactions between the electrode and the electrolyte during cycling. Furthermore, conductive atomic force microscopy (C-AFM) was performed on the electrode surface as a non-destructive technique to determine the difference in surface morphology and conductivity between uncoated and coated electrodes before and after cycling. C-AFM measurements on pristine cathodes before cycling allow clear separation between the conductive carbon additives and the embedded NCM secondary particles, which show an electrically insulating behavior. More importantly, the measurements reveal that the ALD-derived Al2O3 coating with an optimized thickness is thin enough to retain the original conduction properties of the coated electrodes, while thicker coating layers are insulating resulting in a worse cycling performance. After cycling, the surface conductivity of the coated electrodes is maintained, while in the case of uncoated electrodes the surface conductivity is completely suppressed confirming the formation of an insulating cathode electrolyte interface due to the parasitic side reactions. The results not only show the possibilities of C-AFM as a non-destructive evaluation of the surface properties, but also reveal that an optimized coating, which preserves the conductive properties of the electrode surface, is a crucial factor for stabilising the long-term battery performance.

Dyeing of one pair of blue denim jeans consumes about 50–100 liters of water loaded with toxic reducing agents and alkali that remain as effluents in wastewater. Here we introduce an environmentally sound indigo-dyeing technology utilizing a high surface to volume ratio of nanocellulosic materials, which reduces water consumption up to a factor of 25 and eliminates the use of any reducing agent or alkali. This technology secures over 90% dye fixation compared to the 70–80% of conventional dyeing. Lighter or darker shades are approached in a one-step process compared to traditional vat dyeing with multiple (up to 8) dips in a reducing vat followed by oxidation. The dyeing process is as simple as the deposition of a nanocellulose hydrogel loaded with fine natural indigo particles and chitosan over the cotton denim fabric or yarn. The generated nanofibrillated cellulose mesh-like conformal coating encloses indigo particles, whereas chitosan improves the fixation and adhesion of the coating to fabrics via physical cross-linking.

Balancing interfacial stability and Li+ transfer kinetics through surface engineering is a key challenge in developing high-performance battery materials. Although conformal coating enabled by atomic layer deposition (ALD) has shown great promise in controlling impedance increase upon cycling by minimizing side reactions at the electrode-electrolyte interface, the coating layer itself usually exhibits poor Li+ conductivity and impedes surface charge transfer. In this work, we have shown that by carefully controlling postannealing temperature of an ultrathin ZrO2 film prepared by ALD, Zr4+ surface doping could be achieved for Ni-rich layered oxides to accelerate the charge transfer yet provide sufficient protection. Using single-crystal LiNi0.6Mn0.2Co0.2O2 as a model material, we have shown that surface Zr4+ doping combined with ZrO2 coating can enhance both the cycle performance and rate capability during high-voltage operation. Surface doping via controllable postannealing of ALD surface coating layer reveals an attractive path toward developing stable and Li+-conductive interfaces for single-crystal battery materials.

A nanohybrid architecture composed of single-wall carbon nanotube films and graphene heterostructures (SWCNT/graphene) was developed as a three-dimensional (3D) electrode. Atomic layer deposition (ALD) was used for conformal coating of catalytic Pt nanoparticles on the 3D ALD-Pt@SWCNT/graphene nanohybrid architecture for further enhancement of H2 sensing, taking advantage of the large sensing area and conformally coated nanostructures of the catalytic Pt. Remarkably, the H2 response was found to be improved by 50% in the SWCNT/graphene nanohybrid, indicating that graphene provides a more efficient charge transport. The ALD-Pt further enhances the H2 responsivity of the 3D ALD-Pt @SWCNT/graphene nanohybrids. By coating 10 cycles of ALD-Pt on the SWCNT/graphene nanohybrid, the H2 response (2.77%) is approximately twice that (1.4%) of its counterpart without the ALD-Pt. By further optimizing the 3D ALD-Pt@SWCNT/graphene nanohybrids with respect to the ALD-Pt cycle numbers and SWCNT film thickness, a H2 responsivity as high as 7.5% was achieved on the SWCNT/graphene nanohybrid sample with a 560 nm thick SWCNT film and 50 cycles of ALD-Pt.

Conformal coating of ceramic layers (nm-thick) on Ni-rich layered cathode materials is an effective strategy for improving high-temperature longevity of Li-ion batteries (LIBs). In this work, we de...

A conformal coating is a protective chemical material that can be applied as a thin layer on printed circuit board assemblies (PCBAs). The purpose of conformal coating is to prevent the interaction between external environmental factors and the electrical assembly. However, since conformal coating materials have different mechanical properties than electronic components, their use may induce additional mechanical stresses on the board. This study focuses on the effect of having a different coefficient of thermal expansion (CTE) for the conformal coating material from the solder joints of ball grid array (BGA) packages on printed circuit boards (PCBs). Typical lead-free solders have a CTE of less than 25 ppm/°C, while coating materials have a much higher CTE. For example, polyurethane has a CTE around 193 ppm/°C. This CTE mismatch generates stresses in different directions on the solder joints, especially when the assembly is subjected to temperature cycling during its service. In this effort, four samples of PCB assemblies that have BGAs were used in temperature cycling tests. The sample size is nine modules, with each module having at least 272 exposed BGA joints. Three of the samples were coated by a layer of polyurethane and one baseline sample was not coated. Coating thickness was selected to be the experimental design factor. Thus, these three samples, which had different thicknesses (30, 80, and $130~\mu \text{m}$ ), were evaluated and compared against each other and against the noncoated sample. By comparing the four samples, it was found that a thick coating material significantly reduced the lifetime for BGA solder balls by initiating early solder cracks, which propagated and caused complete separation in the solder joint.

Conformal coating of ultrahigh-aspect-ratio nanostructures with functional polymer thin films is highly desirable in many applications, ranging from biosensing to energy storage. Nevertheless, achi...

Conformal coating is commonly used for harsh environment to protect electronics from moisture and chemical contaminants. But the stresses imparted by the conformal coating can cause degradation to the package thermal cycle performance. Full coverage of the component with conformal coating material can prevent potential corrosion induced degradation but imply a local compression stress during thermal cycling, resulting a different thermal cycling performance compared to non-coated components. In this study, 8x8mm2 wafer level chip scale packages (WLCSP) were subjected to 5% NaCl aqueous spray test with and without full conformal coating, then thermal cycled from -40ºC to +125ºC. Weibull reliability statistics indicated that fully conformal coated components experience characteristic life cycle number reduction from 404 cycles to 307 cycles, a 24% lifetime reduction, comparing to no conformal coated, no salt spray test applied components. The correlation between crack propagation and localized recrystallization were compared in a series of cross section analyses using polarized imaging and electro-backscattered diffraction, which revealed that the conformal coating induced a z-axis tension and compression strain during thermal cycling, resulting in an accelerated degradation at the solder interconnect. Linear Laser profilometer measurements showed that fully conformal coated samples experienced a higher z-axis height displacement change relative to non-conformal coated samples when exposed to 125 °C with 10 minutes dwell. To prevent this z-axis strain a reworkable edgebond adhesive was applied with full conformal coating configuration, which demonstrate an increase of characteristic lifecycle number to 2783 cycles, suggesting that the mitigation of the z-axis strain can vastly enhance the thermal cycling performance.

Failure of electronic components of printed circuit boards (PCBs) is a major concern, especially during storage. In the present study, we analyzed different modes of damages noticed on PCBs stored in coastal atmosphere such as leaking capacitors, white residues and attack around soldered joints. Fourier transform infrared spectroscopy, and pH measurements of the electrolyte from good and leaked capacitors indicated that the degraded electrolyte can cause capacitor leakage and subsequent failure. Scanning electron microscopy, energy dispersive x-ray analysis and x-ray photoelectron spectroscopy analysis of the white residue on PCB board showed the presence of phosphorus and oxygen as dendrites, formed due to the leaked electrolyte from capacitors on PCB. PCBs in continuous service with capacitor leak and white residue were also characterized. In this PCB, white residue was predominantly consisting of tin, oxygen and chlorine, which was formed due to corrosion of flux residue under high humid conditions. The damage around soldered joints of stored PCB board was found to be due to re-soldering, over heating which caused damage to the conformal coating and subsequent corrosion due to contaminants from flux residues. Based on the analysis of results, the probable mechanisms for the failure of PCBs are evolved, and the consequences for PCBs on prolonged storage and subsequent operation are also discussed.

The morphology, structure, and optical properties of a composite material based on gold nanoparticles and thin film of amorphous nonstoichiometric silicon oxide (a-SiOx, x = 1.8) have been studied for the first time. Based on the obtained experimental data, it is established that a-SiO1.8 layer provides conformal coating of spherical nanoparticles. An analytical model based on the Mie theory adequately describes the experimental optical properties of gold nanoparticles and composite material in the UV spectral range, as well as the observed variation of the plasmonic peak amplitude during the formation of the composite material.

Pinhole-free and defect-free ultrathin dielectric tunnel barriers (TBs) are a key to obtaining high-tunneling magnetoresistance (TMR) and efficient switching in magnetic tunnel junctions (MTJs). Among others, atomic layer deposition (ALD) provides a unique approach for the fabrication of ultrathin TBs with several advantages including atomic-scale control over the TB thickness, conformal coating, and a low defect density. Motivated by this, this work explores the fabrication and characterization of spin-valve Fe/ALD-Al2O3/Fe MTJs with an ALD-Al2O3 TB thickness of 0.55 nm using in situ ALD. Remarkably, high TMR values of ∼77 and ∼90% have been obtained, respectively, at room temperature and at 100 K, which are comparable to the best reported values on MTJs having thermal AlOx TBs with optimized device structures. In situ scanning tunneling spectroscopy characterization of the ALD-Al2O3 TBs has revealed a higher TB height (Eb) of 1.33 ± 0.06 eV, in contrast to Eb ∼ 0.3-0.6 eV for their AlOx TB counterparts, indicative of significantly lower defect concentrations in the former. This first success of the MTJs with subnanometer thick ALD-Al2O3 TBs demonstrates the feasibility of in situ ALD for the fabrication of pinhole-free and low-defect ultrathin TBs for practical applications, and the performance could be further improved through device optimization.