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Molecular layer deposition (MLD) is an incredibly powerful and flexible tool for designing completely new materials with novel and unique properties. The low temperature layer‐by‐layer approach and the use of highly reactive reactants allows one to combine vastly different organic and inorganic species and construct nanostructures with subnanometer precision. If not limited by the volatility of the reactants involved, the possibilities will be endless. This is most notable for the organic building blocks where an overall low volatility severely limits the toolbox of large molecules with interesting optical and electrical properties such as red‐ox activity and optical conversion. In this work, different strategies for molecular design of large molecules are investigated that allow vaporization while still having the necessary reactivity for MLD growth. Using these strategies, film growth with perylene and porphyrin derivatives, both molecules well known for their functional and optical properties are successfully achieved. With this knowledge, there is an opening to include much larger and more complex organic molecules into the world of vapor phase chemistry. [ABSTRACT FROM AUTHOR]

Abstract Molecular layer deposition (MLD) is an incredibly powerful and flexible tool for designing completely new materials with novel and unique properties. The low temperature layer‐by‐layer approach and the use of highly reactive reactants allows one to combine vastly different organic and inorganic species and construct nanostructures with subnanometer precision. If not limited by the volatility of the reactants involved, the possibilities will be endless. This is most notable for the organic building blocks where an overall low volatility severely limits the toolbox of large molecules with interesting optical and electrical properties such as red‐ox activity and optical conversion. In this work, different strategies for molecular design of large molecules are investigated that allow vaporization while still having the necessary reactivity for MLD growth. Using these strategies, film growth with perylene and porphyrin derivatives, both molecules well known for their functional and optical properties are successfully achieved. With this knowledge, there is an opening to include much larger and more complex organic molecules into the world of vapor phase chemistry.

Currently, there has an ever-growing interest in layered LiNixMnyCozO2 (NMCs, x + y + z = 1) cathode materials for lithium-ion batteries (LIBs) and lithium metal batteries (LMBs), due to their low cost and high capacity. However, they still suffer from a series of issues, such as Li/Ni cation mixing, irreversible phase transition, and transition metal dissolution. These issues result in severe capacity degradation and limited cyclability of NMCs. Recently, atomic and molecular layer deposition (ALD and MLD) have emerged as a novel tool to tackle these issues, featuring their unique capabilities to fine-tailor NMCs' surfaces for stable interfaces and improved electrochemical performance in LIBs and LMBs. In this review, we specially summarize the recent advances of different ALD and MLD coatings on NMCs and discuss their working mechanisms. We expect that this review will stimulate more efforts to further develop better NMCs using novel ALD/MLD coatings. [ABSTRACT FROM AUTHOR]

A combined ALD/MLD (where ALD and MLD stand for atomic and molecular layer deposition, respectively) deposition strategy using TiCl4, H2O and HQ (hydroquinone) as precursors has been applied for the preparation of inorganic–organic thin films on soda-lime glasses. The alternate deposition of TiO2 layers, by pulsing TiCl4/H2O (ALD), and hybrid layers, using TiCl4/HQ (MLD), results in the formation of thin films that are precursors for porous TiO2-coatings after removal of the HQ template by annealing. The coated-glassed show good photocatalytic activity in the degradation of NO with up to 15% reduction of NO concentration in three successive photocatalytic cycles of 5 h each. Surface Scanning Electron Microscopy (SEM) images show that the TiO2-coating is composed of large grains that are made up of finer subgrains resulting in a porous structure with an average pore size of 3–4 nm. Transmission Electron Microscopy (TEM) images show two regions, a porous columnar structure on top and a denser region over the glass substrate. Energy Dispersive X-Ray (EDX) analysis, nanocrystal electron diffraction and Raman spectroscopy confirm the presence of the anatase phase, which, together with the porosity of the material, accounts for the observed photocatalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • A Nb-based hybrid coating for Si anodes was synthesized by MLD and annealing. • The coating provides enhanced tolerance of stress and resistance to side reactions. • A thin, stable LiF-rich SEI layer is established on the Si anode. • Fast Li+ transport kinetics and low stress distribution in the SEI is confirmed. • The Si anode exhibits advantageous rate capability and capacity retention. Silicon material anodes are attractive for a range of high energy density lithium-ion battery applications, but their huge volume expansion, interfacial side reactions, and fast capacity decay are limitations. Herein, molecular layer deposition (MLD) is used to deposit a Nb-based inorganic-organic coating onto casted silicon nanowire (Si NW) electrodes, forming an artificial solid-electrolyte interphase (SEI). Post annealing of the coated composite (Si NW@NbHQ-500) drives a general cross-linking reaction within (-Nb-O-benzene-O-) n units, achieving enhanced mechanical and chemical robustness of the interface. The coating material and its reduced products (Nb4+ species) appear to be involved in a thin and LiF-rich SEI framework, accelerating interfacial Li+ diffusion. With mechanical strain dissipation and natural SEI erosion suppression, the anode exhibits an advantageous rate capability of 940 mAh/g at 4 A/g, a high reversible areal capacity of 4.0 mAh cm−2, an impressive capacity retention with a capacity decay of only ≈0.06 % per cycle over 800 cycles at 1 A/g, as well as a stable full cell electrochemical cycling performance when integrated with a LiFePO 4 cathode. Additionally, SEI modulus test verifies that the Si NW@NbHQ-500 anode undergoes gentle reversible interfacial evolution during cycling with a slight average modulus rise (≈10.3 to 37.9 GPa) from surface to bulk. This work demonstrates the great potential of Nb-based inorganic-organic hybrid nano coatings for mechanical and electrochemical stabilization of silicon anodes. [ABSTRACT FROM AUTHOR]

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Because of its high volumetric heat of oxidation, Zr powder is a promising high energy fuel/additive for rocket propellants. However, the application of Zr powder is restricted by its ultra-high electrostatic discharge sensitivity, which poses great hazards for handling, transportation and utilization of this material. By performing molecular layer deposition of polyimide using 1,2,4,5-benzenetetracarboxylic anhydride and ethylenediamine as the precursors, Zr particles can be uniformly encapsulated by thin layers of the polymer. The thicknesses of the encapsulation layers can be precisely controlled by adjusting the number of deposition cycle. High temperature annealing converts the polymer layer into a carbon coating. Results of thermal analyses reveal that the polymer or carbon coatings have little negative effect on the energy release process of the Zr powder. By varying the thickness of the polyimide or carbon coating, electrostatic discharge sensitivity of the Zr powder can be tuned in a wide range and its uncontrolled ignition hazard can be virtually eliminated. This research demonstrates the great potential of molecular layer deposition in effectively modifying the surface properties of highly reactive metal based energetic materials with minimum sacrifices of their energy densities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomic layer deposition (ALD) used to fabricate metal–organic framework (MOF) materials is reviewed. • Seven combined methods using ALD technology and MOF synthesis are discussed. • Applications of MOF materials related to ALD technology are summarized. • New directions and perspectives for ALD-related MOF materials are provided. Atomic layer deposition (ALD) technology is an effective nanofabrication method used for various nanomaterials and thin films at the atomic level. Metal-organic framework (MOF) materials have a high porosity and specific surface area, and have been widely used in the fields of adsorption, separation, catalysis, sensors and devices. When ALD meets MOFs, some new combination methods can appear. In this review, the advances in MOFs synthesis related to ALD are summarized. These new synthetic methods of MOFs can be divided into seven categories: MOF gas-phase growth via ALD/MLD, MOF solvothermal growth on ALD metal oxide, MOF solvothermal growth and assembled on ALD metal oxide, MOF liquid-phase epitaxy growth on ALD metal oxide, MOF conversion from ALD metal oxide, MOF conversion via hydroxyl double salt from ALD metal oxide and MOF modification via ALD. Meanwhile, the upscaling applications of these ALD-related MOFs, such as in adsorption, separation, catalysis and energy, have further been reviewed. The perspectives of ALD based MOFs have also been provided. Such efforts are expected to provide guidance for developing new synthetic methods of MOFs related to ALD technology and thereby lead to new applications of ALD-related MOFs. [ABSTRACT FROM AUTHOR]

The possibility to deposit purely organic and hybrid inorganic–organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic–organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications.

Organic-inorganic hybrid materials are of great demand not at least for their enormous application potential in flexible devices. Atomic or molecular layer deposition (ALD or MLD) and vapor phase infiltration (VPI) offer novel pathways for the fabrication of such hybrids, but a clear understanding of the chemistry between the vaporized precursors and functional molecules is still lacking. In this work, the interactions between trimethylaluminum (TMA) and the organic functional groups OH, NH2, and NO2 in the respective substituted phenyls, as well as their stability upon exposure to air are investigated. The experimental evidence agrees with theoretically predicted reaction pathways, showing that TMA initially binds to Lewis basic atoms of the investigated functional groups. Depending on the reaction energy barriers, the interaction between TMA and the investigated functional groups may result in either stable chemical bonding or intermediates that decompose upon exposure to humidity. This investigation contributes to the understanding of ALD/MLD and VPI processes at a molecular level and will support a better process optimization. [ABSTRACT FROM AUTHOR]

Tailored organic thin films with designated molecular arrangements are expected to provide a variety of photonic/electronic devices due to their ability to optimize the performance or to generate new functions by controlling the electron wavefunction shapes. Molecular Layer Deposition (MLD), which enables monomolecular-step organic film growth, is one of the promising fabrication processes of tailored organic thin films. In the present report, first, the concept and an experimental demonstration of MLD are described. Next, after three featured capabilities of MLD, namely, ultra-thin/conformal, tailored, and selective organic film growth are presented, applications of MLD based on these capabilities are reviewed, emphasizing polymer multiple quantum dots we have developed. Finally, conceptual proposal of MLD for the molecular targeted drug delivery for cancer therapy is suggested. [ABSTRACT FROM AUTHOR]

This paper is a short review about the principle, preparation, and applications of ultra-thin oxide films prepared by molecular layer deposition (MLD). Porous oxide films, with well-defined porous structures and precisely controlled thicknesses down to several angstroms, can be prepared from dense organic/inorganic hybrid polymer films grown by MLD. The organic constituents in the film can be removed either by calcination at elevated temperatures or mild water etching at room temperature. Because of the layer-by-layer growth process for MLD, the deposited polymer films have regular structures and the removal of organic components from MLD polymer films produces uniform interconnected highly porous structures with a high surface area. For example, porous aluminum oxide films prepared by such a method have both micropores and mesopores with a BET surface area as high as 1250 m 2 /g. Examples of the versatility of the technique for fabrication of novel functional materials for various applications are discussed, including thermally stable, highly selective metal nanoparticle catalysts, defect-free inorganic membranes for gas separation, and photocatalytic layers prepared from titanium alkoxide MLD films. [ABSTRACT FROM AUTHOR]

Titanium alkoxide (titanicone) thin films were coated on large quantities of sub-micron sized silica particles at 100 °C using molecular layer deposition (MLD) in a fluidized bed reactor. Titanium tetrachloride and ethylene glycol were used as precursors. The content of titanium on the particles increased linearly as the number of MLD coating cycles increased. The conformity of the films, with a thickness of ~12 nm, was verified using TEM for silica particles coated with 50 cycles of titanicone. The composition of the titanicone films was confirmed using energy dispersive X-ray spectrometry. Porous titanium oxide films were formed for the particles coated with 50 cycles of titanicone MLD by oxidation in air at 400 °C or by decomposition of the organic components of the titanicone films in the presence of water. The thicknesses of the films were reduced from ~12 nm to ~8 nm after oxidation in air at 400 °C for 1 hr. The effect of aging on the titanicone films was studied at different lengths of aging time in the presence of water. A greatly increased surface area of 48.8 m 2 g −1 was obtained for the particles exposed to water for 24 hr, compared to the as-deposited 50 cycles of titanicone coated sample with a surface area of 7.7 m 2 g −1 . The decomposition of titanicone films, after exposure to water vapor for various lengths of time, was studied using Fourier transform infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Highly structured porous alumina thin films have many practical uses, including membrane applications and catalyst encapsulation. One route to synthesizing these films that offers exceptional control over film thickness to several angstroms starts with the molecular layer deposition (MLD) of an aluminum alkoxide (alucone) film. Oxidizing the alucone film removes the organic component and produces the desired nanoporous alumina. The pore size can be controlled by selection of the length of the carbon chain in the polymer film. In this study, 500nm silica nanoparticles were coated with 10–40cycles of alucone using a three-step ABC MLD process. Trimethylaluminum, ethanolamine, and maleic anhydride were used as precursors. The organic component of the alucone films was removed in air by calcination at elevated temperature or in water at room temperature. It is shown that the pore size of the porous films can be increased from 0.6 to 0.8nm by depositing an alucone film having longer carbon chains. Film surface area, composition, thickness, and pore size were measured, confirming that the ABC MLD process can produce high quality porous alumina films and provide a pathway to tune nanopore size in these films. [Copyright &y& Elsevier]

The article describes the usage of molecular layer deposition (MLD) for the conformal coating of ultra-thin aluminum alkoxide (alucone) polymer films on primary silica and titania nanoparticles within a fluidized bed reactor. The usage of in situ mass spectrometry to demonstrate the self-limiting nature of alucone MLD film growth as a function of the individual exposures of trimethylaluminum and ethylene glycol is noted. Also noted is the fact that the highest growth rate was found to coincide with the lowest sample temperature.

The recent advancement of semiconductor devices to the near-atomic scale necessitated the development of atomic layer processing methods, including molecular layer deposition (MLD). This gas-phase deposition technique creates semipermeable polymer films with precise control of composition and thickness. Herein, MLD was used to produce thin-film composite reverse osmosis membranes. Aromatic polyamide films as thin as 0.5 nm were applied to NF270 nanofiltration membranes using m -phenylenediamine and trimesoyl chloride. Within two molecular layers, desalination performance was affected. As film thickness increased to 15 nm (48 MLD cycles), performance progressed from nanofiltration to reverse osmosis metrics in terms of salt rejection and water permeance. With film thickness > 5 nm, rejection values exceeded a small sampling of commercial membranes. In all cases, a tradeoff between rejection and permeance was observed. Atomic force microscopy measurements indicate that MLD enhancement led to removal of small-scale roughness features and resulted in a root mean square roughness difference of <0.1 nm from the substrate. These initial MLD studies represent a novel processing approach that offers a potential pathway for the fabrication of membranes with finely tailored properties. [Display omitted] • MLD added an ultrathin MPD-TMC polyamide active layer to commercial NF membranes. • Progressive MLD systematically altered flux/rejection metrics from NF to RO values. • Controlled increase of MLD layer thickness increased rejection but decreased flux. • Atomic force microscopy revealed that MLD removed small-scale roughness features. [ABSTRACT FROM AUTHOR]

Infrared (IR) spectroscopy is a powerful technique to characterize the chemical structure and dynamics of various types of samples. However, the signal-to-noise-ratio drops rapidly when the sample thickness gets much smaller than penetration depth, which is proportional to wavelength. This poses serious problems in analysis of thin films. In this work, an approach is demonstrated to overcome these problems. It is shown that a standard IR spectroscopy can be successfully employed to study the structure and composition of films as thin as 20 nm, when the layers were grown on porous substrates with a well-developed surface area. In contrast to IR spectra of the films deposited on flat Si substrates, the IR spectra of the same films but deposited on porous ceramic support show distinct bands that enabled reliable chemical analysis. The analysis of Zn-S ultrathin films synthesized by atomic layer deposition (ALD) from diethylzinc (DEZ) and 1,5-pentanedithiol (PDT) as precursors of Zn and S, respectively, served as proof of concept. However, the approach presented in this study can be applied to analysis of any ultrathin film deposited on target substrate and simultaneously on porous support, where the latter sample would be a reference sample dedicated for IR analysis of this film. [ABSTRACT FROM AUTHOR]

Area selective molecular layer deposition (MLD) is a promising technique for achieving micro- or nanoscale patterned organic structures. However, this technique still faces challenges in attaining high selectivity, especially at large MLD cycle numbers. Here, we illustrate a new strategy for achieving high quality patterns in selective film deposition on patterned Cu/Si substrates. We employed the intrinsically selective adsorption of an octadecylphosphonic acid self-assembled monolayer (SAM) on Cu over Si surfaces to selectively create a resist layer only on Cu. MLD was then performed on the patterns to deposit organic films predominantly on the Si surface, with only small amounts growing on the Cu regions. A negative potential bias was subsequently applied to the pattern to selectively desorb the layer of SAMs electrochemically from the Cu surface while preserving the MLD films on Si. Selectivity could be enhanced up to 30-fold after this treatment.

The possibility to deposit purely organic and hybrid inorganic-organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic-organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications.