Passivation Layer Research Articles

Plasma surface treatment of amorphous Ga2O3 thin films for solar-blind ultraviolet photodetectors

Recently, amorphous gallium oxide (a-Ga2O3) thin films are gaining more and more attention due to their advantages of low cost and low temperature growth. However, a-Ga2O3 solar-blind ultraviolet photodetectors are plagued by issues such as slow response speed and high dark current. In this work, radio frequency magnetron sputtering was used for a-Ga2O3 deposition, and a novel approach of plasma treatment (including oxygen, argon and hydrogen plasmas) was employed to tailor the device performance using a plasma-enhanced chemical vapor deposition system. It is demonstrated that: (i) the oxygen atoms and ions in the oxygen plasma effectively reduce the oxygen vacancy concentration and improve the respond speed of a-Ga2O3 photodetectors; (ii) the argon ions in the argon plasma create additional defects (such as dangling bonds and oxygen vacancies) and improve the responsivity of a-Ga2O3 photodetectors; (iii) the hydrogen atoms in the hydrogen plasma may incorporate into the film and form an ultra-thin passivation layer near the surface, which gives rise to a balance between responsivity and response speed. Finally, through the detailed analysis of the optical emission spectra and photoelectric performance, the underlying physical mechanism based on the energy band diagram has been proposed to interpret the obtained experimental results.

Reliability of Quasi-vertical GaN on Silicon Schottky Barrier Diodes With SiO₂ Passivation Layer Under On-State Stress Bias

Reliability of Quasi-vertical GaN on Silicon Schottky Barrier Diodes With SiO₂ Passivation Layer Under On-State Stress Bias

Surface microstructure evolution and enhanced properties of Ti-6Al-4V using scanning electron beam

Enhanced surface properties of the Ti-6Al-4V alloy are crucial for optimizing its overall performance and reliability. In this study, scanning electron beam treatment was employed to enhance its surface properties. The results demonstrate a nonlinear decrease in hardness with increasing depth, while the surface microhardness increased to 422.6 HV0.1, representing a 1.4 times enhancement compared to the substrate. The wear volume was decreased from 0.5045 mm³ before treatment to 0.2498 mm³, resulting in a >2 times enhancement in wear resistance. Additionally, the corrosion current density of the treated material decreased by an order of magnitude, while the corrosion potential and charge transfer resistance increased. These improvements in surface properties can be attributed to the treatment with a scanning electron beam, which induces phase transformation and refines the microstructure into more acicular α' phases. This process enhances surface hardness and facilitates the formation of a more robust passive layer, thereby enhancing the material's wear resistance and corrosion resistance. This study provides valuable insights and methodologies for enhancing the surface properties of Ti-6Al-4V alloy.

Enhancement of copper mobilization using acidic AlCl3 − rich lixiviant

Copper (Cu) extraction from low-grade ores is limited by the formation of secondary minerals that can passivate the surfaces of Cu-sulphide minerals in these ores. Hence, a novel approach utilizing AlCl3 as a lixiviant was developed to modify coupled dissolution-reprecipitation processes at the mineral interface. The formation of Al-rich phases instead of Fe-hydroxysulphates enhanced Cu extraction through combined ferric-iron and proton-promoted dissolution. AlCl3 accelerated chalcopyrite and bornite dissolution by forming soluble intermediate Cu-phases (e.g., covellite) at consistently high Eh (550–650 mV) and acidity due to the Lewis acid property of AlCl3. X-ray diffraction analysis revealed that Na-bearing jarosite [(K0.61Na0.41)Fe3(SO4)2(OH)] and sideronatrite [Na2Fe(SO4)2(OH)(H2O)] formation in lixiviants without AlCl3 decreased Fe3+(aq) availability for Cu-sulphide minerals dissolution. In contrast, significant amounts of AlSO4+(aq) formed in the AlCl3-rich lixiviant at pH 1–3, which reduced the sulphate activity and decreased the saturation state of the Fe-hydroxysulphates. Further, AlCl3 promoted the formation of amorphous, porous Al-rich phases, facilitating quick Fe diffusion through the passivating layer and improving Cu recovery compared to lixiviants containing CaCl2, NaCl, or acid-only.

Discovery of white etching areas in high nitrogen bearing steel X30CrMoN15-1: A novel finding in rolling contact fatigue analysis

White etching areas (WEA) and white etching cracks (WEC) are frequently linked to premature bearing failure in conventional high carbon bearing steels like 100Cr6 (SAE 52100). In contrast, no WEA/WEC has yet been reported for the high nitrogen bearing steel X30CrMoN15-1 (SAE AMS 5898). Thus, the present study proves for the first time that X30CrMoN15-1 is also susceptible to develop WEA/WEC under rolling contact fatigue (RCF) when pre-charged with hydrogen. RCF tests conducted in parallel without hydrogen pre-charging resulted in RCF damage only, which identifies hydrogen as an active agent for WEA/WEC formation in X30CrMoN15-1. These findings correspond to the fact that hydrogen diffusion during RCF is often considered to cause or accelerate the formation of WEA/WEC. Additionally, it is observed that the M2(C, N) and M23C6 precipitates of the martensitic microstructure of the X30CrMoN15-1 do not entirely decompose during the WEA formation process as observed for M3C precipitates in 100Cr6. In conclusion, the results for X30CrMoN15-1 strongly suggest that the formation of WEA is driven by a hydrogen-activated local severe plastic deformation process, which initiates continuous dynamic recrystallisation, leading to the characteristic nano-ferritic grains observed in WEA. Also, the highly stable and self-regenerating passive chromium-oxide layer of X30CrMoN15-1 mitigates the risk of WEA/WEC failure during typical RCF operation by hindering the formation and adsorption of ionic hydrogen. Hence, this study emphasises the importance of protecting the base material against hydrogen ingress to delay WEA/WEC formation.

Development and Characterization of N2O-Plasma Oxide Layers for High-Temperature p-Type Passivating Contacts in Silicon Solar Cells.

Full-area passivating contacts based on SiOx/poly-Si stacks are key for the new generation of industrial silicon solar cells substituting the passivated emitter and rear cell (PERC) technology. Demonstrating a potential efficiency increase of 1 to 2% compared to PERC, the utilization of n-type wafers with an n-type contact at the back and a p-type diffused boron emitter has become the industry standard in 2024. In this work, variations of this technology are explored, considering p-type passivating contacts on p-type Si wafers formed via a rapid thermal processing (RTP) step. These contacts could be useful in conjunction with n-type contacts for realizing solar cells with passivating contacts on both sides. Here, a particular focus is set on investigating the influence of the applied thermal treatment on the interfacial silicon oxide (SiOx) layer. Thin SiOx layers formed via ultraviolet (UV)-O3 exposure are compared with layers obtained through a plasma treatment with nitrous oxide (N2O). This process is performed in the same plasma enhanced chemical vapor deposition (PECVD) chamber used to grow the Si-based passivating layer, resulting in a streamlined process flow. For both oxide types, the influence of the RTP thermal budget on passivation quality and contact resistivity is investigated. Whereas the UV-O3 oxide shows a pronounced degradation when using high thermal budget annealing (T > 860 °C), the N2O-plasma oxide exhibits instead an excellent passivation quality under these conditions. Simultaneously, the contact resistivity achieved with the N2O-plasma oxide layer is comparable to that yielded by UV-O3-grown oxides. To unravel the mechanisms behind the improved performance obtained with the N2O-plasma oxide at high thermal budget, characterization by high-resolution (scanning) transmission electron microscopy (HR-(S)TEM), X-ray reflectometry (XRR) and X-ray photoelectron spectroscopy (XPS) is conducted on layer stacks featuring both N2O and UV-O3 oxides after RTP. A breakup of the UV-O3 oxide at high thermal budget is observed, whereas the N2O oxide is found to maintain its structural integrity along the interface. Furthermore, chemical analysis reveals that the N2O oxide is richer in oxygen and contains a higher amount of nitrogen compared to the UV-O3 oxide. These distinguishing characteristics can be directly linked to the enhanced stability exhibited by the N2O oxide under higher annealing temperatures and extended dwell times.

Gate mesa terminal with drain-field-plated β-Ga2O3 MOSFET with ultra-high power figure of merit

In this article, a novel gate mesa terminal (GMT) device structure incorporating a drain field plate is proposed. This design features mesa terminals with varying bevel angles positioned atop the gate. The objective is to enhance the breakdown voltage (Vbr) and reduce the on-resistance (Ron) of the lateral β-Ga2O3 metal-oxide-semiconductor field-effect transistor (MOSFET). Through the implementation of the GMT structure, the peak electric field within the β-Ga2O3 MOSFET is redirected towards the passivation layer. This effectively mitigates the electric field in the epitaxial layer, thereby increasing Vbr. The optimal values for Vbr, specific on-resistance (Ron,sp) and maximum transconductance (gm) across various GMT structures are 4827 V, 9.9 mΩ·cm2 and 15.32 mS/mm, respectively. These metrics represent a 2.63-fold, 0.88-fold, and 1.25-fold improvement compared to the non-GMT structure. Additionally, when the doping concentration of epitaxial layer is 1 × 1016 cm−3, the GMT achieves an enhanced threshold voltage of +0.26 V. By simulating different bevel angles, field plate parameters, epitaxial layer doping concentrations, and mesa thicknesses, an optimal power figure of merit (PFOM) of 1.914 GW cm−2 is attained. This innovative design introduces a fresh concept for the development of the next generation of high voltage and high-power devices rated above 4 KV.

Nickel release from 316L stainless steel following a Ni-free electroplating cycle

Electroplating can induce nickel release even from 316L stainless steel, typically considered safe. In this work, the influence of different electroplating processes and surface treatments on nickel release was evaluated. The nickel release was tested according to the EN 1811 standard. The impact of surface roughness on nickel release was assessed by comparing polished and unpolished samples. Results indicate that internal stresses can worsen nickel release, while increasing the thickness of the precious metal layer is beneficial. To corroborate our hypothesis, it was verified that coatings obtained through physical vapor deposition (PVD), without removing the passivation layer of the steel, did not release nickel. For these reasons, we identified the main cause of nickel release as the combined effect of the removal of the passivation layer of stainless steel and the microporosity of the electroplating process.

Ru Passivation Layer Enables Cu-Cu Direct Bonding at Low Temperatures with Oxidation Inhibition.

Stacking semiconductor chips allows for increased packing density within a given footprint and efficient communication between different functional layers of the chip, leading to higher performance, improved speed, and reduced power consumption. In such vertical stacking, achieving homogeneous electrical and mechanical bonding between heterogeneous chips is crucial, which is termed Cu to Cu direct bonding (CCDB) technology. However, conventional CCDB required a high temperature of over 250 °C to allow Cu diffusion and a vacuum condition for inhibiting Cu oxidation, limiting its practical utilization. Here, we propose that the covering of the Ru layer enables a reliable CCDB as low as 200 °C without concerns regarding oxidation. The bonding strength was as high as 2.24 MPa, and it was endurable at the -45 and 125 °C temperature cycle test for 500 cycles. Through microscopic analysis, we have identified that Cu diffuses through the intercluster boundaries of the Ru layer and moves to the surface, and these atomic Cu ions are recrystallized at the bonding interface, enabling stable bonding at lower temperatures. Specifically, we observed a trade-off between Cu diffusion distance and oxidation inhibition capability depending on the thickness of Ru and found that a 6 nm-thick Ru is optimal, balancing these factors.

Mechanochemical carbonation of recycled concrete fines: Towards a high-efficiency recycling and CO2 sequestration

The relative slow carbonation efficiency for conventional wet and dry carbonation of recycled concrete fines (RCF) limits its resource industrial utilization. In this study, an innovative mechanochemical carbonation (MC) method was developed. The carbonation kinetics, phase assemblage and microstructure evolution of RCF during the MC process were extensively examined. The results exhibited a substantial enhancement in the carbonation efficiency and CO2 utilization rate, as evidenced by achieving a notable carbonation degree within 10 min. This accomplishment surpassed what could be achieved even after a prolonged 2 h period of wet carbonation, and the CO2 uptake capacity and utilization rate achieved via MC reached >0.3 g-CO2/g-RCF and 80 %, respectively. The superior performance of MC was ascribed to the influence of mechanochemical effects. These effects contributed to the refinement in the geometrical characteristics of RCF, exfoliation of the passivating layers, and facilitation of CO2 dissolution, which favored the structural disintegration of RCF and carbonation progress. Another distinctive aspect of MC treatment was the production of a greater proportion of metastable CC characterized by reduced crystalline size, which was attributed to modifications in the carbonation environment and the structural alterations induced by mechanochemical effects. Moreover, the precipitation of silica gels commenced at approximately 4 min in the MC process, a notably earlier onset when compared with wet carbonation; additionally, a greater abundance of silica gels was observed in the current MC procedure, resulting from the higher carbonation degree caused by mechanochemical effects. The encouraging conclusions in the present work validated the feasibility of producing carbonated RCF more efficiently and paved the way for future industrial practice.

Multifunctional biomolecular corona-inspired nanoremediation of antibiotic residues.

Facing complex and variable emerging antibiotic pollutants, the traditional development of functional materials is a "trial-and-error" process based on physicochemical principles, where laborious steps and long timescales make it difficult to accelerate technical breakthroughs. Notably, natural biomolecular coronas derived from highly tolerant organisms under significant contamination scenarios can be used in conjunction with nanotechnology to tackling emerging contaminants of concern. Here, super worms (Tubifex tubifex) with high pollutant tolerance were integrated with nano-zero valent iron (nZVI) to effectively reduce the content of 17 antibiotics in wastewater within 7 d. Inspired by the synergistic remediation, nZVI-augmented worms were constructed as biological nanocomposites. Neither nZVI (0.3 to 3 g/L) nor worms (104 to 105 per liter) alone efficiently degraded florfenicol (FF, as a representative antibiotic), while their composite removed 87% of FF (3 μmol/L). Under antibiotic exposure, biomolecules secreted by worms formed a corona on and modified the nZVI particle surface, enabling the nano-bio interface greater functionality, including responsiveness, enrichment, and reduction. Mechanistically, FF exposure activated glucose-alanine cycle pathways that synthesize organic acids and amines as major metabolites, which were assembled into vesicles and secreted, thereby interacting with nZVI in a biologically response design strategy. Lactic acid and urea formed hydrogen bonds with FF, enriched analyte presence at the heterogeneous interface. Succinic and lactic acids corroded the nZVI passivation layer and promoted electron transfer through surface conjugation. This unique strategy highlights biomolecular coronas as a complex resource to augment nano-enabled technologies and will provide shortcuts for rational manipulation of nanomaterial surfaces with coordinated multifunctionalities.

Inhibited Passivation by Bioinspired Cell Membrane Zn Interface for Zn-Air Batteries with Extended Temperature Adaptability.

Due to the slow dynamics of mass and charge transfer at Zn|electrolyte interface, the stable operation of Zn-air batteries (ZABs) is challenging, especially at low temperature. Herein, inspired by cell membrane, a hydrophilic-hydrophobic dual modulated Zn|electrolyte interface is constructed. This amphiphilic design enables the quasi-solid-state (QSS) ZABs to display a long-term cyclability of 180 h@50mAcm-2 at 25°C. Moreover, a record-long time of 173 h@4mAcm-2 at -60°C is also achieved, which is almost threefolds of untreated QSS ZABs. Control experiments and (in situ) characterization reveal that the growth of insulating ZnO passivation layers is largely inhibited by tuned hydrophilic-hydrophobic behavior. Thus, the enhanced transfer dynamic of Zn2+ at Zn|electrolyte interface from 25 to -60°C is attained. As an extension, the QSS Al-air batteries (AABs) with bioinspired interface also show unprecedented discharge stability of 420 h@1mAcm-2 at -40°C, which is about two times of untreated QSS AABs. This bioinspired-hydrophilic-hydrophobic dual modulation strategy may provide a reference for energy transform and storage devices with broad temperature adaptability.

The Exponential Shapeshifting Response of N-Vinylcaprolactam Hydrogel Bilayers Due to Temperature Change for Potential Minimally Invasive Surgery.

Poly (N-vinylcaprolactam) (PNVCL) and poly (N-isopropylacrylamide) (PNIPAm) are two popular negatively temperature-responsive hydrogels, due to their biocompatibility, softness, hydrophilicity, superabsorbency, viscoelasticity, and near-physiological lower critical solution temperature (LCST). These characteristics make them ideal for biomedical applications. When combined with other materials, hydrogel expansion induces the morphing of the assembly due to internal stress differences. Our recent developments in NVCL hydrogel, enhanced by nanoclay incorporation, have driven us to the creation of a bilayer structure to study its shapeshifting response across various temperatures. This study focused on the bending behaviour of bilayer samples composed of an active hydrogel layer and a passive non-swellable layer. Using photopolymerisation, circular discs and rectangular bilayer samples of varying sizes were fabricated. Homogeneous circular samples demonstrated that hydrogel density increased proportionally with temperature, with the swelling ratio exhibiting two distinct rates of change below and above its LCST. In bilayer samples, the volume of the passive layer influenced bending, and its optimal volume was identified. The investigation revealed that geometry affected the overall bending effect due to changes in the passive layer stiffness. Lastly, a temperature-responsive gripper capable of picking up objects several times its own weight was demonstrated, highlighting the potential of NVCL hydrogels as bioactuators for minimally invasive surgery.

22.56% total area efficiency of n-TOPCon solar cell with screen-printed Al paste

Screen-printing Ag paste on the rear side of the Tunnel Oxide Passivated Contact solar cells (TOPCon) is still the mainstream method to form electrodes. However, the high price of precious metals increases the cost of TOPCon cells. Al is a cheap and high-performance conductor, and its work function is compatible with the rear side of TOPCon cells. In this study, we used a UV pulse laser (355 nm, 10 ps) to ablate the rear side SiNx passivation layer of TOPCon cells and then printed Al paste with different weight percentages of silicon (Si-wt.%) on the phosphorus-doped polycrystalline silicon (n+-poly-Si) layer to reduce the cost. We investigated the damage mechanism of laser on SiOx/n+-poly-Si/SiNx passivation structure and the contact mechanism between Al paste and n+-poly-Si layer. The results show that the Voc of SiOx/n+-poly-Si/SiNx passivation structure reduced about 6–7 mV when the laser energy density was 0.431 J/cm2. We got the best electrical performance of TOPCon cells printed with Al paste (25 wt%-29 wt% silicon). The open-circuit voltage (Voc) and the conversion efficiency (Eff), have reached 663.60 mV and 22.56 % respectively. Although the efficiency was 9.40 % relative lower than that of TOPCon cells printed with Ag paste, but the cost of Al paste only accounted for 10 % of Ag paste. In the future, the highest Eff of TOPCon solar cells printed with Al paste on the rear side are expected to reach the commercial TOPCon based on Ag paste, which applies laser doping selective emitter technology (SE) and bifacial poly-Si passivation structure.

In Vitro Corrosion of Polyester-Coated Magnesium Alloy under pH-Static Conditions.

The resorption rate of bioresorbable implants requires tuning to match the desired field of application. The use of Mg as implant material is highly advantageous, as it provides sufficient mechanical strength combined with its biodegradability. Consequently, the implant vanishes after it has served its intended purpose, allowing the complete restoration of natural tissue and organ function. However, a biodegradable Mg implant requires a biodegradable coating to slow the rate of Mg corrosion, as a permanent coating would negate the benefits of using Mg as an implant material. Therefore, degradable polymers are the materials of choice, especially polyester-based coatings, such as PLLA, as they have been proven in clinical practice over the long term. Within this work, the degradation retarding effect of a physical barrier in form of four clinically relevant polyester-based coatings, poly-l-lactide (PLLA), poly-l-lactide-co-glycolide (PLGA), poly(l-lactide-co-PEG) triblock copolymer (PLLA-co-PEG), and polydioxanone (PDO), is investigated in vitro under pH-static conditions using CO2 gas to compensate pH changes due to Mg corrosion. Coating thicknesses of 7.5 to 8.3 μm were comparable to commercially available stent systems. Quantitative analysis of magnesium concentration in buffered test medium by a photometric assay allows real-time monitoring. Shielding effect of different polyesters through polymer coating and formation of a protective passivation layer beneath the polymer coating was observed and characterized using SEM and EDX techniques. Our finding was that even imperfect polymer layers provide a considerable protective effect, and the used in vitro setup matches reported in vivo observations regarding elemental composition of corrosion products.

Balancing current density and electrolyte flow for improved zinc-air battery cyclability

Zinc-air batteries (ZABs), known for their high energy density and environmental friendliness, are emerging as promising solutions for sustainable energy storage. However, the irregular deposition of zinc on electrodes hinders the widespread utilization of rechargeable ZABs due to limited durability and stability. This study investigates the role of electrolyte flow in enhancing zinc electrodeposition and overall performance in zinc-air flow batteries (ZAFBs) at high current densities. We explore the interplay between current density, flow rate, and their influence on electrode surface morphology and the removal of the passivating zinc oxide layer to improve battery efficiency and lifespan. Using advanced in-situ synchrotron radiation x-ray tomography, we found that incorporating flowing electrolyte at specific current densities results in rounded dendrite tips, thinner and more uniform deposition layers, and improved zinc adhesion. Imaging and electrochemical analyses further reveal that flowing electrolyte enhances zinc morphology, reduces charge transfer resistance, diminishes passivation, and lowers galvanostatic charge/discharge polarization across various current densities, thereby improving battery cycling performance. Notably, the impact of flowing electrolyte is more pronounced at a moderate current density of 50 mA/cm2 compared to lower or higher currents. Our findings underscore the importance of electrolyte flow and current density management in developing high-performance ZAFBs, providing valuable insights for their future commercialization.

Enhanced interfacial and cycle stability of 4.6 V LiCoO2 cathode achieved by surface modification of KAlF4

Lithium cobalt oxide is one of the most popular cathode materials for lithium-ion batteries. Due to its relatively low capacity, increasing the output voltage is often necessary to release more capacity. However, subjecting cathode materials to high charging potentials inevitably induces surface-side reactions, compromising the integrity of the crystal structure and accelerating capacity degradation. Therefore, the stability of cathode materials at high voltage becomes crucial for lithium-ion batteries. In this study, we employed the ternary compound KAlF4 (KAF) as a surface modification coating for LiCoO2 (LCO). With the optimized ratio (1 wt%) of KAF, coated LCO cathodes exhibited enhanced capacity retention, excellent cycling, and rate stability. In the high voltage range of 3.0–4.6 V, the specific capacity of the initial discharge at a rate of 0.5 C reached 198.30 mA h g−1. Remarkably, the coated LCO retained 91.56 % of its initial capacity after 200 cycles at 0.5 C. Even at a high rate of 5 C, the coated sample retained a discharge capacity of 120.87 mA h g−1, significantly higher than that of bare LCO (80.24 mA h g−1). After a thorough investigation into the structure changes before and after cycling, we elucidated the mechanism of KAF coating in improving the stability of high-voltage LCO cathodes. The results indicated that KAF forms a stable passivation layer on the surface of LCO, which suppresses cracking and corrosion during charging and discharging, eventually stabilizes the crystal structure, and enhances the cycling stability of LCO.

Electrical Performance, Loss Analysis, and Efficiency Potential of Industrial‐Type PERC, TOPCon, and SHJ Solar Cells: A Comparative Study

ABSTRACTCurrently, the efficiency of p‐type passivated emitter and rear contact (PERC) cells has been growing at an absolute efficiency of 0.5% per year and has reached 23%–23.5% in mass production while getting closer to its theoretical efficiency limit. n‐Type tunnel oxide passivated contact (TOPCon) and silicon heterojunction (SHJ) cells with their superior “passivating selective contacts” technology were the most interesting photovoltaics (PV) technology in the industry. The effect of different passivated contact layers with respect to their influence on the J0, J0,metal, ρc, and the carrier selectivity (S10) and the loss analysis and efficiency potential of industrial‐type PERC, TOPCon, and SHJ solar cells were studied and compared. The results showed that TOPCon structure with a high passivation performance and good optical performance is more suitable for bifacial solar cell and the highest theoretical limiting efficiency with metal shading on the n‐type Si wafer (ηb,e,h,m,max) can be achieved to 27.62%. Although SHJ structure with the highest passivation performance but the worst optical performance owing to the parasitic absorption of a‐Si:H layer and high contact resistivity, the value of ηb,e,h,m,max is 0.7% lower than that of TOPCon solar cells. PERC structure has superior optical performance than SHJ structure, but due to poor passivation performance, the ηb,e,h,m,max is only 26.42%. The next‐generation products may be heterojunction back‐contact (HBC) and TOPCon back‐contact (TBC) cells with high ηb,e,h,m,max of 28.12% and 27.99%, respectively. Exploiting a perfect passivation of the noncontact area, the wide process window and low cost are required and transferring these new concepts to industrial solar cell production will be the next major challenge.

Double Perovskite Interlayer Stabilized Highly Efficient Perovskite Solar Cells.

Metal halide perovskite solar cell (PSC) technology has an impressive power conversion efficiency (PCE) exceeding 26.1% and demonstrates cost-effective manufacturing. However, the stability of these PSCs poses a significant challenge, hindering their widespread manufacturing and commercialization. To tackle the degradation issue inherent in PSCs, surface passivation techniques, particularly employing a thin layer of two-dimensional (2D) perovskites, create a 2D/3D heterostructure. Beyond this, the exploration of metal halide double perovskites adds a new dimension to the chemical and band gap phase space of materials for optoelectronic applications. In this study, we leverage a wide band gap double perovskite interlayer to enhance the stability of 3D metal halide perovskite. Specifically, the double perovskite nanoparticle Cs2AgBiBr6, with its substantial band gap of 2.2 eV and exceptional air stability, is utilized. Through optimization, a Cs2AgBiBr6-treated PSC achieves an open-circuit voltage of 1.12 V and an impressive PCE of 19.52%. Additionally, the Cs2AgBiBr6 passivation layer proves to be effective in bolstering the stability of PSCs. This work demonstrates an additional strategy and design motif to simultaneously increase the PCE of PSCs along with achieving improved stability.

Etch characteristics of cobalt thin films using high density plasma of CH3COCH3/Ar gas mixture

Co thin films masked with SiO2/Si3N4 layers were etched using a high-density plasma of a CH3COCH3/Ar gas mixture. As the concentration of CH3COCH3 increased, the etch rate of the Co thin films and etch selectivity decreased. Optimal etch profiles of the Co films without redeposition were achieved owing to the formation of Co compounds and a passivation layer, which facilitated a high degree of anisotropy. Moreover, the etch characteristics of the Co films were examined using the ICP RF power, dc-bias voltage to the substrate, and process pressure. The active species in plasmas and Co compounds formed during etching were investigated using optical emission spectroscopy and X-ray photoelectron spectroscopy. Finally, the Co thin films patterned with 300 nm lines were etched using a CH3COCH3/Ar gas mixture under optimized etch conditions. The findings suggest that a CH3COCH3/Ar gas mixture can serve as an effective etch gas for fabricating dry-etched Co thin films.