Application Of Atomic Layer Deposition Research Articles

ALD with Enhanced Nucleation on Polymeric Separator for Improved Li-S Batteries

Lithium-sulfur (Li-S) batteries, known for their exceptional energy densities, are at the forefront of the next generation of energy storage systems. However, their practical application is hindered by the polysulfide shuttle effect, which significantly impairs discharge capacity and cycling stability. This research introduces a novel solution to these challenges through the use of atomic layer deposition (ALD) of Al₂O₃ on commercial polypropylene/polyethylene/polypropylene (PP/PE/PP) separators.ALD is a thin-film deposition technique that allows for precise control of layer thickness and composition at the atomic scale. ALD is characterized by its ability to produce extremely uniform and conformal layers, making it an ideal method for applications where surface chemistry plays a critical role, such as in battery separators. The technique is particularly advantageous in applications requiring high precision and control, like in our approach to enhancing Li-S batteries.In our study, the inert separator was treated with UV ozone to enhance the nucleation of ALD precursors, with the goal of reducing polysulfide shuttling. The use of ALD-modified separators in batteries demonstrated a marked increase in specific capacity, reaching approximately 1150 mAh/g, and reduced overpotential, indicative of improved kinetic efficiency. Further, we explored the structural and chemical modifications of the separator, employing X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Our findings indicate that ALD of Al₂O₃ on the separators significantly improved the adsorption of polysulfides, thereby mitigating the shuttle effect.In addition to improved polysulfide interaction, we also examined the impact on polysulfide adsorption on the formation of the solid-electrolyte interphase (SEI). Our results showed that modified batteries exhibited no polysulfide presence on the anode, suggesting a stable and effective SEI. This observation is significant, as it indicates that our approach enhances specific capacity and cycling stability by controlling the formation of a more effective SEI.Overall, our research demonstrates how strategic modifications at the separator level, particularly through the application of ALD and UV ozone, can significantly enhance the overall performance of Li-S batteries. By leveraging the unique advantages of ALD, especially through Al₂O₃ deposition, we provide a viable pathway to enhance the efficiency and stability of Li-S batteries.

Influences of deposition conditions on atomic layer deposition films for enhanced performance in perovskite solar cells

Atomic layer deposition (ALD) is a key technology for fabricating functional layers in perovskite solar cells, as it can deposit pinhole-free films with atomic-level thickness and tunable composition on high-aspect-ratio surfaces. Various deposition conditions have significant effects on the growth, physical, and chemical properties of ALD films, which, in turn, critically influences the performance of associated devices. Here, we review the reaction mechanisms underlying ALD and summarize how variables, such as precursors, deposition temperatures, and substrates, impinge upon the quality of ALD films and the related devices. We emphasize the role of substrate in determining the nucleation and growth behavior of ALD films, which has been overlooked in previous reviews. Finally, we highlight the potential application of ALD in efficient perovskite solar cells in terms of carrier transport, encapsulated, and buffer layers, especially for tandem cells.

Performance Enhancement of Nickel Manganese Cobalt Oxide Cathodic Material for Solid-State Battery Technology by Surface Engineering

Batteries as any other electronic devices are affected by parasitic phenomena including physical processes and chemical reactions occurring within the battery materials as well as their interfaces. The phenomena lead to degradation in performance, impose operation restrictions and potentially make devices unsafe.Solid-state, lithium-metal-based, batteries show promise to meet electric vehicle market requirements, but technical challenges to overcome rapid degradation and cost-effective processing remains. Cathode/electrolyte interfacial side reactions can lead to passivating layer formation, thus increasing cell resistance, unwanted additional overvoltage, and ultimately capacity loss. These phenomena are exacerbated in solid-to-solid contact between solid state electrolytes, active materials, and electronic conductive agents. Therefore, electrode manufacturing design is required to mitigate these issues.Within this work we have evaluated Spray Drying (SD) and Atomic Layer Deposition (ALD) coating processes to engineer the cathode/ electrolyte interface of SSBs, thus improving performance and overall cell cycle life. Cathode materials coating is utilised as an effective strategy to mitigate the degradation of the interface. SD is classically utilised in the food and pharma industries, and it has recently been expanded to include the synthesis/shaping of battery electrode materials as a versatile and robust methodology that can be easily scaled up. ALD is a widely exploited technique in the semiconductor (SC) industry based on self-limiting chemical reactions to deposit stoichiometrically-fixed, defect-free and nanometric-thick materials on surfaces. As such, the application of ALD to coat powders in the battery community is innovative and currently under development.Cathodic materials such as NMC (Nickel Manganese Cobalt Oxides) have been investigated, as the need for improving the capacity retention is strong for high-content (>80%) nickel cathodes. Indeed, ALD utilised to coat NMC powder provides a nanometric thick layer of a dielectric but ionic conductive metal oxide. Optimisation of aluminium oxide shell on a core of polycrystalline high nickel material has been investigated with surface engineering. In parallel, we have been exploring the benefit of SD to create an NMC811 powder showing a decorated structure using two different approaches. Indeed, we have either used preformed metal oxide nanoparticles dispersed in an NMC suspension or synthesised a metal oxide layer on top of the NMC in-situ by a chemical reaction during the spray process.Morphological and chemical characterisation of the products have been crucial to develop the coating processes. Electrochemical Impedance Spectroscopy (EIS) probed the engineered cathode/ electrolyte interface within half- and full-coin cell configuration. Rate performance and long-term cycling evaluation has driven the design of an oxide-based lithium metal solid state battery.Alumina coated powder NMC showed longer capacity retention than raw materials when tested in coin cell batteries. The cells were assembled using thin lithium metal anode, Lithium-Lanthanum Zirconium Oxide (LLZO) electrolyte, and surface-engineered NMC811 supported by aluminium current collector. Key words:Surface Engineering, Coatings, Solid-State Batteries (SSB), Spray Dry, Atomic Layer Deposition (ALD), Preformed Nanoparticles, Nickel Manganese Cobalt Oxide (NMC), NMC811, Lithium Lanthanum Zirconium Oxide (LLZO), Interfaces.

In Pursuit of Next Generation N-Heterocyclic Carbene-Stabilized Copper and Silver Precursors for Metalorganic Chemical Vapor Deposition and Atomic Layer Deposition Processes

Volatile, reactive, and thermally stable organometallic copper and silver complexes are of significant interest as precursors for the metalorganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) of ultra-thin metallic films. Well-established CuI and AgI precursors are commonly stabilized by halogens, phosphorous, silicon, and oxygen, potentially leading to the incorporation of these elements as impurities in the thin films. These precursors are typically stabilized by a neutral and anionic ligand. Recent advancements were established by the stabilization of these complexes using N-heterocyclic carbenes (NHCs) as neutral ligands. To further enhance the reactivity, in this study the anionic ligand is sequentially changed from β-diketonates to β-ketoiminates and β-diketiminates, yielding two new CuI and two new AgI NHC-stabilized complexes in the general form of [M(NHC) (R)] (M = Cu, Ag; R = β-ketoiminate, β-diketiminate). The synthesized complexes were comparatively analyzed in solid, dissolved, and gaseous states. Furthermore, the thermal properties were investigated to assess their potential application in MOCVD or ALD. Among the newly synthesized complexes, the β-diketiminate-based [Cu(tBuNHC) (NacNacMe)] was identified to be the most suitable candidate as a precursor for Cu thin film deposition. The resulting halogen-, oxygen-, and silicon-free CuI and AgI precursors for MOCVD and ALD applications are established for the first time and set a new baseline for coinage metal precursors.

Emerging Atomic Layer Deposition Technology toward High‐k Gate Dielectrics, Energy, and Photocatalysis Applications

The precise design and efficient development of nanoscale materials at the atomic level has enabled high‐end renewable energy storage, conversion devices, and large‐scale environmental governance equipment. Atomic layer deposition (ALD) is a new vapor‐phase technology for precise surface thin‐film preparation, and is outstanding with self‐limiting reactions, large deposition area, adjustable film composition, film uniformity, angstrom thickness control, and low temperature. With these characteristics, ALD plays an important role in many industry and research fields. This review briefly introduces the principle, main technical advantages, and applications of ALD, including high‐k gate dielectrics, solar cells, fuel cells, and photocatalysis. The progress of the ALD technology in preparation and application of photocatalyst is emphatically reviewed, and the large‐scale application of ALD in photocatalytic thin‐film materials is prospected.

In Vitro Study of Zirconia Surface Modification for Dental Implants by Atomic Layer Deposition.

Zirconia is a promising material for dental implants; however, an appropriate surface modification procedure has not yet been identified. Atomic layer deposition (ALD) is a nanotechnology that deposits thin films of metal oxides or metals on materials. The aim of this study was to deposit thin films of titanium dioxide (TiO2), aluminum oxide (Al2O3), silicon dioxide (SiO2), and zinc oxide (ZnO) on zirconia disks (ZR-Ti, ZR-Al, ZR-Si, and ZR-Zn, respectively) using ALD and evaluate the cell proliferation abilities of mouse fibroblasts (L929) and mouse osteoblastic cells (MC3T3-E1) on each sample. Zirconia disks (ZR; diameter 10 mm) were fabricated using a computer-aided design/computer-aided manufacturing system. Following the ALD of TiO2, Al2O3, SiO2, or ZnO thin film, the thin-film thickness, elemental distribution, contact angle, adhesion strength, and elemental elution were determined. The L929 and MC3T3-E1 cell proliferation and morphologies on each sample were observed on days 1, 3, and 5 (L929) and days 1, 4, and 7 (MC3T3-E1). The ZR-Ti, ZR-Al, ZR-Si, and ZR-Zn thin-film thicknesses were 41.97, 42.36, 62.50, and 61.11 nm, respectively, and their average adhesion strengths were 163.5, 140.9, 157.3, and 161.6 mN, respectively. The contact angle on ZR-Si was significantly lower than that on all the other specimens. The eluted Zr, Ti, and Al amounts were below the detection limits, whereas the total Si and Zn elution amounts over two weeks were 0.019 and 0.695 ppm, respectively. For both L929 and MC3T3-E1, the cell numbers increased over time on ZR, ZR-Ti, ZR-Al, and ZR-Si. Particularly, cell proliferation in ZR-Ti exceeded that in the other samples. These results suggest that ALD application to zirconia, particularly for TiO2 deposition, could be a new surface modification procedure for zirconia dental implants.

Engineering of Conformal Electrode Coatings by Atomic Layer Deposition for Aqueous Na-ion Battery Electrodes

The application of atomic layer deposition on active material particles or as conformal layers directly on electrodes is an effective and viable approach for protecting the battery materials from degradation. Al2O3, TiO2, and HfO2 coatings are applied on NaTi2(PO4)3, which is among the most studied negative electrode materials for aqueous Na-ion batteries. The coated electrodes are characterized in terms of electrochemical kinetics, charge capacity retention, and electrochemical impedance spectra. Al2O3, a widely used protective coating in non-aqueous batteries, is shown to be insufficient to suppress parasitic processes and is eventually dissolved by reaction with hydroxide during extended cycling in aqueous Na2SO4. However, this process provides a local buffering effect making the protective action of this coating mainly of chemical nature. TiO2 is found to be very resistant to increase in pH and remains almost intact during electrochemical cycling. However, we provide strong evidence that TiO2 itself is electrochemically active in aqueous electrolytes at negative potentials. The protonation of TiO2 leads to an additional increase in local pH which is detrimental to NaTi2(PO4)3 and results in even faster capacity loss than in uncoated electrodes. Only HfO2 is found to be sufficiently stable and electrochemically inert ALD coating for negative NaTi2(PO4)3 electrodes operating in aqueous electrolytes.

Release Rate Studies of 5-Aminosalacylic Acid Coated with Atomic Layer-Deposited Al2O3 and ZnO in an Acidic Environment.

5-Aminosalicylic acid (5-ASA) is a first-line defense drug used to treat mild cases of inflammatory bowel disease. When administered orally, the active pharmaceutical ingredient is released throughout the gastrointestinal tract relieving chronic inflammation. However, delayed and targeted released systems for 5-ASA to achieve optimal dose volumes in acidic environments remain a challenge. Here, we demonstrate the application of atomic layer deposition (ALD) as a technique to synthesize nanoscale coatings on 5-ASA to control its release in acidic media. ALD Al2O3 (38.0 nm) and ZnO (24.7 nm) films were deposited on 1 g batch powders of 5-ASA in a rotatory thermal ALD system. Fourier transform infrared spectroscopy, scanning electron microscopy, and scanning/transmission electron microscopy establish the interfacial chemistry and conformal nature of ALD coating over the 5-ASA particles. While Al2O3 forms a sharp interface with 5-ASA, ZnO appears to diffuse inside 5-ASA. The release of 5-ASA is studied in a pH 4 solution via UV-vis spectroscopy. Dynamic stirring, mimicking gut peristalsis, causes mechanical attrition of the Al2O3-coated particles, thereby releasing 5-ASA. However, under static conditions lasting 5000 s, the Al2O3-coated particles release only 17.5% 5-ASA compared to 100% release with the ZnO coating. Quartz crystal microbalance-based etch studies confirm the stability of Al2O3 in pH 4 media, where the ZnO films etch 41× faster than Al2O3. Such results are significant in achieving a nanoscale coating-based drug delivery system for 5-ASA with controlled release in acidic environments.

(Invited) ALD Coatings for Li-Ion Battery and All-Solid-State Battery Applications

Lithium-ion batteries (LIBs) are essential for modern life, and their improvement is crucial for the more widespread adoption of electric vehicles.[1] Layered lithium transition metal oxides, such as LiNixCoyMnzO2 (often referred to as NCM or NMC), are among the most widely used cathode active materials (CAMs) for automotive applications, owing to their technological maturity and high energy density. However, they typically require a surface coating for stabilizing interfaces, both in liquid-electrolyte based LIBs and in solid-state battery (SSB) environments. For the preparation of protective CAM coatings, atomic layer deposition (ALD) stands out with its ability to produce conformal films on complex substrates.This presentation encompasses several examples of successful improvements in cycling performance of Ni-rich NCM CAMs in LIBs and SSBs by ALD of binary oxides. The low-temperature deposition of AlxOy onto ready-to-use cathode sheets will be discussed.[2] ALD or ALD-related surface protection enables increased stability by suppressing detrimental surface corrosion and metal leaching (side reactions) in LIBs.[2,3] Moreover, we report about the application of ALD coatings to Ni-rich NCM CAMs in SSBs with lithium thiophosphate solid electrolytes. Specifically, the effect that both HfO2 and ZrO2 have on the cell cyclability will be shown, with emphasis placed on the role of post annealing.[4] [1] Goodenough et al. J. Am. Chem. Soc. 2013, 135, 1167.[2] Neudeck et al. Sci. Rep. 2019, 9, 5328.[3] Neudeck et al. Chem. Commun. 2019, 55, 2174.[4] Kitsche et al. ACS Appl. Energy Mater. 2021, 4, 7338.

Chemical Vapor Deposition of Wide-Bandgap p-Type Semiconductor Cuprous Iodide for Optoelectronic Device Applications

Continuous, pinhole-free thin films of transparent conductive materials (TCMs) with p- and n-type conductivity are critical components of optoelectronic devices including photovoltaics (PV), transparent electronics, and LEDs [1]. TCMs with n-type conductivity are widely available in the form of semiconducting oxides [2]; however, p-type TCMs (hole transport materials, HTMs) with suitable conductivity are comparatively rare [1]. Particularly in the rapidly growing field of thin film perovskite PV, device-quality thin films of HTMs with high stability and conductivity are urgently needed to replace the organic HTMs typically employed in perovskite PV research [3]. As such, techniques to deposit inorganic HTM thin films are desired.With a focus on applying HTMs in optoelectronic devices at the commercial scale, these materials must be deposited by a scalable technique yielding thin, continuous, pinhole-free films. Chemical vapor deposition (CVD) is a highly scalable thin film deposition technique widely used in industry, with a proven ability to yield high-quality thin films on large-area substrates [4]. A variety of n-type TCMs are accessible by CVD techniques, but few CVD methods exist for p-type TCMs; examples include atomic layer deposition of NiOx and VOx [5].The cuprous halides (CuX, X = Cl, Br, I), which are optically transparent p-type semiconductors with bandgaps ~3 eV, are promising inorganic HTM candidates. Cuprous iodide is of particular interest due to its low resistivity (~10-2 Ohm·cm), high hole concentration and mobility (~1019 cm-3 and ~1-10 cm2V-1s-1, respectively), and its valence band maximum position (ionization potential: 5.0-5.4 eV), which is well-aligned with common perovskite absorber materials [6]. While CuI crystallite arrays have been obtained by metal-organic CVD [7], CVD of continuous CuI thin films has only been achieved by a two-step vapor conversion process, requiring initial deposition of a copper chalcogen followed by vapor-phase conversion to the halide [6].Our group has recently published a CVD technique enabling direct deposition of continuous CuBr thin films via CVD reaction between hydrogen bromide and vinyltrimethylsilane(hexafluoroacetylacetonato)copper(I) [Cu(hfac)(vtms)] [8], and this technique has been extended to deposition of CuI. X-ray photoelectron spectroscopy indicates pure CuI films with an atomic ratio of approximately 1:1 Cu:I, and x-ray diffraction confirms deposition of γ-CuI. Similar to our observations for CuBr films, substrate identity has significant effects on CuI film continuity. Progress towards CVD of continuous CuI films on substrates of interest for practical application in optoelectronic devices will be discussed, with a particular focus on perovskite PV.[1] A. N. Fioretti and M. Morales-Masis, "Bridging the p-type transparent conductive materials gap: synthesis approaches for disperse valence band materials," J. Photon. Energy, 10, 042002 (2020).[2] M. Morales-Masis, S. De Wolf, R. Woods-Robinson, J. W. Ager, and C. Ballif, "Transparent Electrodes for Efficient Optoelectronics," Adv. Electron. Mater., 3, 1600529 (2017).[3] B. Gil, A. J. Yun, Y. Lee, J. Kim, B. Lee, and B. Park, "Recent Progress in Inorganic Hole Transport Materials for Efficient and Stable Perovskite Solar Cells," Electron. Mater. Lett., 15, 505 (2019).[4] R. Gordon, "Chemical Vapor Deposition of Coatings on Glass," J. Non-Cryst. Solids, 218, 81 (1997).[5] J. A. Raiford, S. T. Oyakhire, and S. F. Bent, "Applications of atomic layer deposition and chemical vapor deposition for perovskite solar cells," Energy Environ. Sci., 13, 1997 (2020).[6] R. Heasley, L. M. Davis, D. Chua, C. M. Chang, and R. G. Gordon, "Vapor Deposition of Transparent, p-Type Cuprous Iodide Via a Two-Step Conversion Process," ACS Appl. Energy Mater., 1, 6953 (2018).[7] V. Gottschalch, S. Blaurock, G. Benndorf, J. Lenzner, M. Grundmann, and H. Krautscheid, "Copper iodide synthesized by iodization of Cu-films and deposited using MOCVD," J. Cryst. Growth, 471, 21 (2017).[8] C. M. Chang, L. M. Davis, E. K. Spear, and R. G. Gordon, "Chemical Vapor Deposition of Transparent, p-Type Cuprous Bromide Thin Films," Chem. Mater., 33, 1426 (2021).

Molecular Layer Deposition for Stable Lithium Metal Anode: From Composition Design to Mechanism Study

Energy storage systems with higher gravimetric energy density is highly desirable to fulfil the increasing requirement for various applications. One of the most promising direction is the development of next-generation batteries. Lithium (Li) metal is considered as the ‘Holy Grail’ for the anode materials owing to its ultrahigh capacity and low electrochemical potential [1]. Nevertheless, the application of Li metal as anode material has long been hindered due to some great challenges, such as poor cycling stability and short life span. The serious side reaction between metallic Li and organic electrolyte results in the formation of solid electrolyte interphase (SEI). On one hand, the SEI serves as a passivation layer on the surface which partially prevents further side reaction. On the other hands, the undesired dendrite growth cannot be prevented by SEI due to its heterogeneous and unstable properties [2]. Modification on the interphase to tune and stabilize its property has been considered as an approach to improve the cycling performance of Li metal anode. Recent studies on stabilizing SEI for Li metal anode can be divided into two categories, in-situ and ex-situ approach. In-situ approach refers to the design of electrolyte using electrolyte additives or adjusting the concentration of Li salt. Ex-situ approach refers to the construction of surface coating, including metal oxides, phosphates, and polymers on Li prior to electrochemical cycling [3]. An ideal SEI requires high ionic conductivity, good mechanical property, thin thickness, and high chemical stability. Nevertheless, it is still challenging to fulfil all the requirements of an ideal SEI for long-life and stable Li metal anode.Recent studies have demonstrated the application of Atomic layer deposition (ALD) and Molecular layer deposition (MLD) on the interphase modification of batteries. As a coating technique, ALD is can be applied to deposit inorganic materials such as various metal oxides. It shows unique advantages such as low depositing temperature, uniform film morphology and precise control over thickness in nanoscale [4-6]. As a derivative technique to ALD, MLD is widely used to fabricated inorganic-organic hybrid or pure polymer coatings. MLD still possesses the advantages of ALD and provides additional advantages such as tuneable mechanical property and adjustable coating composition. Our group previously reported ALD metal oxide and MLD metalcone as artificial SEI for metallic Li anodes [7-8].In this report, we demonstrate a type of MLD Polyurea (PU) coatings for metallic Li to modify the SEI layer [9-10]. The cycling life and stability has been improved upon the application of MLD PU. The surface chemistry of PU on Li is characterized by TOF-SIMS and XPS to investigate the evolution of SEI and the role of polymer coating. The results showed that MLD coating can effectively suppress the dendrite growth and remain stable under repeated Li plating/stripping. Furthermore, the nitrogen-containing polar groups in PU can effectively regulate the Li-ion flux and lead to a uniform Li deposition. In our following study, aluminium crosslinkers have been introduced into PU to achieve a hybrid nanoscale polymeric protective film with tuneable composition and improved stiffness. Owing to the improvement in the mechanical property, the protected Li can deliver much stable performance for more than 350 h with a higher cycling capacity of 2 mAh cm−2 without a notable increase in overpotential. Moreover, a stable charge/discharge cycling in Li–O2 batteries with the protected Li can be maintained for more than 600 h. Our study on MLD protected Li provides guidance on the rational design of electrode interfaces and opens new opportunities for the fabrication of next‐generation energy storage systems.[1] D. Lin, Y. Cui, et al, Nature Nanotechnology, 2017, 12, 194-206[2] X. Cheng, Q. Zhang, et al, Chemical Reviews, 2017, 117, 10403-10473[3] X. Cheng, Q. Zhang, et al, Adv. Sci., 2016, 3, 1500213[4] Y. Zhao, X. Sun, ACS Energy Lett. 2018, 3, 4, 899–914[5] Y. Zhao, X. Sun, et al, Joule, 2018, 2, 12, 2358-2604[6] Y. Zhao, X. Sun, et al, Chem. Soc. Rev., 2021, 50, 3889-3956[7] Y. Zhao, X. Sun, et al, Small Methods, 2018, 2, 1700417[8] K. R. Adair, X. Sun et al, Angew. Chem. Int. Ed., 2019, 58, 15797.[9] Y. Sun, X. Sun, et al, Adv. Mater., 2019, 31, 1806541[10] Y. Sun, X. Sun, et al, Adv. Energy Mater., 2020, 10, 2001139.

(Invited) The Application of ALD and ALE Passivated MicroLED Display

Micro LED has been engaged to the next generation display technology and evolved for various applications from several electronic manufacturers and institutions. The less than 10×10 μm2 area of micro-LEDs is desired for the high pixel per inch (PPI) of micro display but the sidewall effect from etching process will drop the quantum efficiency. Therefore, a good passivation process is essential to be introduced into micro-LED process to overcome the efficiency droop issue. The passivation technique of atomic layer deposition (ALD) enables to improve the sidewall damages from dry etching and hence the quantum efficiency of micro-LEDs can be enhanced [1, 2]. Furthermore, the improvement can be enhanced within smaller size of micro LEDs. In particular, due to the excellent uniformity and step coverage passivation by ALD Al2O3 thin films, the interest in efficient ALD equipment has gradually increased. The atomic layer etching (ALE) is an advance etching process that promises an excellent depth control in shallow device structures. This paper provides an overview of ALD and ALE process for improving the micro-LED performance.The epitaxial structure of the micro-LED structures was grown on a c-plane sapphire substrate using metal-organic chemical vapor deposition (MOCVD). Following the development of MOCVD, a transparent and ohmic p-contact of indium tin oxide (ITO) with a thickness of 100 nm was deposited by electron-beam evaporation as a transparent and ohmic p-contact. The ITO layer can result in efficient electrical current spreading and provide a transparent emission window for topside emitting devices. N-type GaN, p-type GaN, and the multiple quantum wells (MQWs) active region, which consists of twelve pairs of InGaN wells and a GaN barrier with an emission wavelength of around 445 nm, are the major epitaxial layers. The growth phases of micro-LED processing included mesa etching, ohmic contact metallization, sidewall passivation deposition using Al2O3 of thickness 21.3 nm and SiO2 of thickness 300 nm, and interconnects. The inductively coupled plasma (ICP) dry etching process is used for the mesa etching method, and SiO2 and Al2O3 passivation layers are deposited using PECVD and ALD techniques. Since Al2O3 and SiO2 are well-known dielectric materials for photonic applications, they were selected. Because of the field effect passivation produced by negative fixed charges, Al2O3 has emerged as a unique passivation material for commercial solar cells. The passivation layers tend to prevent surface recombination and reabsorption of emitted light near the etched surface during forward-biased activity. Following the deposition of the dielectric passivation layers, a hole was created using the ICP etching technique for the deposition of metal contacts. The electrode metal consisted of 50/300 nm of Ti/Au for p- and n- metal contacts deposited using electron-beam evaporation followed by rapid thermal annealing. The process flow of ALD passivated micro-LED is shown in Fig. 1(a).Fig. 1(b) showed the effect of the ALD-Al2O3 passivation technique on the EQE enhancement of µ-LEDs. According to the literature, the peak EQE of a small LED is considerably small due to the surface and nonradiative recombination of the mesa layer caused by plasma-assisted dry etching. ALD sidewall passivation is an important method for reducing plasma damage in LEDs. We can observe the 21.3 nm Al2O3 passivation on micro-LED in Fig.1(a). Therefore, Fig. 1 (b) presents the EQEs of 10 × 10-µm2 µ-LEDs with and without an Al2O3 passivation layer deposited using the ALD technology for reducing plasma damage. Compared with the device not subjected to ALD-Al2O3 passivation, the 10 × 10-µm2 array subjected to ALD-Al2O3 passivation exhibited an EQE enhancement of 37.5%. This result proves that ALD sidewall passivation can effectively reduce the sidewall damage caused by SRH nonradiative recombination and thus increase the EQE of small LEDs.

The Prospect of the Electroless Atomic Layer Deposition (ALD) for Applications in Semiconductor Technology

The metallic thin films are widely used for in semiconductor technology. Surface morphology, thickness and purity of the film are the key attributes determining its functionality 1 , 2. Recent developments indicate that Cu/liner/TaN structures where liner could be either Co, Ru or Rh and TaN serves as barrier are of particular interest. The electrochemical doping of Zn with liner material to develop barrier-less Cu structures has been demonstrated3. In this talk we demonstrate a protocol to deposit conformal Cu thin film on Co by replacement of Zn overlayer without etching Co. EDTA and BTA are used for corrosion inhibition of Co film once all Zn capping layer is consumed in galvanic displacement with Cu. TEM, XPS and EDS indicate conformal Cu layer deposition Co layer underneath being intact. The second part of the talk focuses on electroless ALD application for deposition of Pt and Rh layers on Cu, Au or Ru substrates. 4 , 5. Surface reflectivity changes during electroless ALD serves as an indicator of surface roughness evolution after each cycle. Surface morphology after 20 electroless ALD cycles is studied by STM and AFM. Cyclic voltammetry illustrates catalytically active Pt and Rh surface after deposition. All electroless ALDs are performed at room temperature in glove box with inert atmosphere. Surface selective, self-terminating deposition and precise control over the film thickness are achieved demonstrating potential of this deposition method for scale up and industrial applications. Ahmadi, K., Wu, D., Dole, N., R. Monteiro, O. & R. Brankovic, S. Tuning Surface Chemoresistivity of Au Ultrathin Films Using Metal Deposition via Surface-Limited Redox Replacement of the Underpotentially Deposited Pb Monolayer. ACS Sensors 4, 2442–2449 (2019).Wu, D. et al. Pb Monolayer Mediated Thin Film Growth of Cu and Co: Exploring Different Concepts. Journal of The Electrochemical Society 166, D3013–D3021 (2019).Kailash Venkatraman, Yezdi Dordi, A. J. Electrochemical doping of thin metal layers employing underpotential deposition and thermal treatment. 1 (2019).Wu, D. et al. Electroless Deposition of Pb Monolayer: A New Process and Application to Surface Selective Atomic Layer Deposition. Langmuir 34, 11384–11394 (2018).Wu, D. et al. Underpotential and Electroless Pb Monolayer Deposition on Ru(0001). Journal of The Electrochemical Society 166, D359–D365 (2019). Figure 1

Applications of Atomic Layer Deposition in Design of Systems for Energy Conversion.

There is a huge demand for clean energy conversion in all industries. The clean energy production processes include electrocatalytic and photocatalytic conversion of water to hydrogen, carbon dioxide reduction, nitrogen conversion to ammonia, and oxygen reduction reaction and require novel cheap and efficient photo- and electrocatalysts and their scalable methods of fabrication. Atomic layer deposition is a thin film deposition method that allows to deposit thin layers of catalysts on virtually any surface of any shape, size, and porosity in an even and easy to control manner. Here the state of the art in applications of atomic layer deposition in the clean energy production and the opportunities it represents for the whole field of the photo- and electrocatalysis for a sustainable future are reviewed.

Understanding the roles of atomic layer deposition in improving the electrochemical performance of lithium-ion batteries

Rechargeable lithium-ion batteries have been widely used as energy storage devices in electric vehicles and other smart devices due to their excellent properties, such as high energy and power densities, long-term service life, and acceptable cost. The electrochemical performance of the materials in a lithium-ion battery system determines the performance of the battery, so it is essential that the electrochemical properties of these materials be improved. Atomic layer deposition is a versatile thin film coating technique for surface functionalization that can deposit a highly uniform thin film of nanoscale thickness on battery components, and it has been proven to improve the electrochemical performance of materials that operate in a lithium-ion battery system, such as rate capability, interface stability, and cycling life. This review paper focuses on recent advances of application of atomic layer deposition in lithium-ion batteries and summarizes the roles of such thin film coatings in improving the electrochemical performance of batteries. The present review summarizes and classifies the latest understanding of improvement mechanisms proposed by researchers according to different components in lithium-ion batteries, including cathodes, anodes, separators, and solid electrolytes. This review will not only help researchers in this field to comprehend the roles of atomic layer deposition thin film coating for improving the performance of various components in a battery system, but will also help them choose appropriate coating materials on battery components. In addition, we briefly discuss the limitations of atomic layer deposition in lithium-ion battery applications and the challenges that it faces in the future.

Advanced Applications of Atomic Layer Deposition in Perovskite‐Based Solar Cells

Perovskite solar cells (PSCs) have shown remarkable photovoltaics progress with a record‐eminent power conversion efficiency (PCE) of 25.2%. Therefore, the PSCs are potential candidates to replace traditional crystalline silicon‐based solar cells. However, the PCE and stability of PSCs need to be improved for successful commercialization. Recently, the atomic layer deposition (ALD) technology is successfully applied to fabricate the encapsulation layer, which overcomes the long‐standing issues of perovskite‐based solar cells based on others’ pioneering work on ALD in PSCs several years ago. The organic–inorganic alternating encapsulation structure that the team researched has exhibited a water vapor transmittance rate of 1.3 × 10−5 g m−2 day−1, which is the lowest value among the reported thin‐film encapsulation layers of PSCs. Herein, the properties of ALD and how it is used in PSCs, such as device architecture, surface modification, passivation, and encapsulation, which result in higher PCEs and excellent stability, are discussed. In addition, the potential significance of applying ALD in the manufacture of tandem and flexible PSCs and the synthesis of high‐quality perovskite materials is also analyzed.

Application of Atomic Layer Deposition for the Formation of Nanostructured ITO/Al2O3 Coatings

Application of Atomic Layer Deposition for the Formation of Nanostructured ITO/Al2O3 Coatings

Cryo-ePDF: Overcoming Electron Beam Damage to Study the Local Atomic Structure of Amorphous ALD Aluminum Oxide Thin Films within a TEM.

Atomic layer deposition (ALD) provides uniform and conformal thin films that are of interest for a range of applications. To better understand the properties of amorphous ALD films, we need an improved understanding of their local atomic structure. Previous work demonstrated measurement of how the local atomic structure of ALD-grown aluminum oxide (AlOx) evolves in operando during growth by employing synchrotron high-energy X-ray diffraction (HE-XRD). In this work, we report on efforts to employ electron diffraction pair distribution function (ePDF) measurements using more broadly available transmission electron microscope (TEM) instrumentation to study the atomic structure of amorphous ALD-AlOx. We observe electron beam damage in the ALD-coated samples during ePDF at ambient temperature and successfully mitigate this beam damage using ePDF at cryogenic temperatures (cryo-ePDF). We employ cryo-ePDF and reverse Monte Carlo (RMC) modeling to obtain structural models of ALD-AlOx coatings formed at a range of deposition temperatures from 150 to 332 °C. From these model structures, we derive structural metrics including stoichiometry, pair distances, and coordination environments in the ALD-AlOx films as a function of deposition temperature. The structural variations we observe with growth temperature are consistent with temperature-dependent changes in the surface hydroxyl density on the growth surface. The sample preparation and cryo-ePDF procedures we report here can be used for the routine measurement of ALD-grown amorphous thin films to improve our understanding of the atomic structure of these materials, establish structure–property relationships, and help accelerate the timescale for the application of ALD to address technological needs.

Atomic Layer Deposition of 2D Metal Dichalcogenides for Electronics, Catalysis, Energy Storage, and Beyond

Abstract2D transition metal dichalcogenides (TMDCs) are among the most exciting materials of today. Their layered crystal structures result in unique and useful electronic, optical, catalytic, and quantum properties. To realize the technological potential of TMDCs, methods depositing uniform films of controlled thickness at low temperatures in a highly controllable, scalable, and repeatable manner are needed. Atomic layer deposition (ALD) is a chemical gas‐phase thin film deposition method capable of meeting these challenges. In this review, the applications evaluated for ALD TMDCs are systematically examined, including electronics and optoelectonics, electrocatalysis and photocatalysis, energy storage, lubrication, plasmonics, solar cells, and photonics. This review focuses on understanding the interplay between ALD precursors and deposition conditions, the resulting film characteristics such as thickness, crystallinity, and morphology, and ultimately device performance. Through rational choice of precursors and conditions, ALD is observed to exhibit potential to meet the varying requirements of widely different applications. Beyond the current state of ALD TMDCs, the future prospects, opportunities, and challenges in different applications are discussed. The authors hope that the review aids in bringing together experts in the fields of ALD, TMDCs, and various applications to eventually realize industrial applications of ALD TMDCs.

(Invited) Advanced ALD Applications

CMOS device feature size down-scaling is still continuous. Nowadays it reaches 5nm and beyond. The technology development in semiconductor industry encounters many new challenges. As consequences, new materials and new techniques are required to meet the challenges.At 45nm technology node, Atomic Layer Deposition (ALD) is introduced for gate stack process. Since then ALD is being used more and more in advanced technology nodes because of its intrinsic process features, e.g. accurate thickness control and excellent step coverage etc. Especially for the reduced feature sizes, ALD exhibits as a powerful technique, not only in gate stack, but also in advanced patterning process (SADP and SAQP) and advanced metallization barrier materials etc.Hf-based hik material deposited by ALD is widely used in logic gate stack and memory capacitor. Recently Hf-based materials are continuously getting more attentions due to its intrinsic features. It is reported that Hf-based materials can exhibit different resistor stage. Therefore it can be used as memristor in ReRAM. People also report Hf-based materials can be crystalized into orthorhombic phase and thus exhibit ferroelectric characteristics[1,3]. Based on this feature, it can be used in NCFET and FeRAM. In this paper, we can going to review the applications of Hf-based materials deposited by ALD in new memory fields.Although device down-scaling is still going on, the challenges are tremendous. As an alternative, 3D-IC packaging, stacks different chip together and increases the packaging density and chip performance. Therefore, recently 3D-IC packaging is getting more and more attractive. However, there are many constrains in 3D-IC packaging, e.g. low thermal budget, high aspect ratio structure, excellent film quality etc.. ALD is gradually accepted in 3D-IC packaging due to its intrinsic features. In this paper, we are going to discuss some ALD applications in advanced 3D-IC packaging.REFERENCES[1] J. Müller et al, NanoLetters, vol. 12, no. 8, pp. 4318-4323, 2012.[2] M. H. Lee et al, IEEE J. of the Electron Device Society, vol. 3, no. 4, pp. 377-381, 2015.[3] M. H. Lee et al, IEEE Electron Device Letter, vol. 36, no. 4, pp. 294-296, 2015.