In the past decade, atomic layer deposition (ALD) has become an important thin film deposition technique for applications in nanoelectronics, catalysis, and other areas due to its high conformality on 3-D nanostructured substrates and control of the film thickness at the atomic level. The current applications of ALD primarily involve binary metal oxides, but for new applications there is increasing interest in more complex materials such as doped, ternary, and quaternary materials. This article reviews how these multicomponent materials can be synthesized by ALD, gives an overview of the materials that have been reported in the literature to date, and discusses important challenges. The most commonly employed approach to synthesize these materials is to combine binary ALD cycles in a supercycle, which provides the ability to control the composition of the material by choosing the cycle ratio. Discussion will focus on four main topics: (i) the characteristics, benefits, and drawbacks of the approaches that currently exist for the synthesis of multicomponent materials, with special attention to the supercycle approach; (ii) the trends in precursor choice, process conditions, and characterization methods, as well as underlying motivations for these design decisions; (iii) the distribution of atoms in the deposited material and the formation of specific (crystalline) phases, which is shown to be dependent on the ALD cycle sequence, deposition temperature, and post-deposition anneal conditions; and (iv) the nucleation effects that occur when switching from one binary ALD process to another, with different explanations provided for why the growth characteristics often deviate from what is expected. This paper provides insight into how the deposition conditions (cycle sequence, temperature, etc.) affect the properties of the resultant thin films, which can serve as a guideline for designing new ALD processes. Furthermore, with an extensive discussion on the nucleation effects taking place during the growth of ternary materials, we hope to contribute to a better understanding of the underlying mechanisms of the ALD growth of multicomponent materials.

For atomic layer deposition (ALD) of doped, ternary, and quaternary materials achieved by combining multiple binary ALD processes, it is often difficult to correlate the material properties and growth characteristics with the process parameters due to a limited understanding of the underlying surface chemistry. In this work, in situ Fourier transform infrared (FTIR) spectroscopy was employed during ALD of zinc-oxide, tin-oxide, and zinc-tin-oxide (ZTO) with the precursors diethylzinc (DEZ), tetrakis(dimethylamino)tin (TDMASn), and H2O. The main aim was to investigate the molecular basis for the nucleation delay during ALD of ZTO, observed when ZnO ALD is carried out after SnO2 ALD. Gas-phase FTIR spectroscopy showed that dimethylamine, the main reaction product of the SnO2 ALD process, is released not only during SnO2 ALD but also when depositing ZnO after SnO2, indicating incomplete removal of the ligands of the TDMASn precursor from the surface. Transmission FTIR spectroscopy performed during ALD on SiO2 powder revealed that a significant fraction of the ligands persist during both SnO2 and ZnO ALD. These observations provide experimental evidence for a recently proposed mechanism, based on theoretical calculations, suggesting that the elimination of precursor ligands is often not complete. In addition, it was found that the removal of precursor ligands by H2O exposure is even less effective when ZnO ALD is carried out after SnO2 ALD, which likely causes the nucleation delay in ZnO ALD during the deposition of ZTO. The underlying mechanisms and the consequences of the incomplete elimination of precursor ligands are discussed.

A synthetic route toward hybrid MoS 2 -based materials that combines the 2D bonding of MoS 2 with 3D networking of aliphatic carbon chains is devised, leading to a film with enhanced electrocatalytic activity. The hybrid inorganic-organic thin films are synthesized by combining atomic layer deposition (ALD) with molecular layer deposition (MLD) using the precursors molybdenum hexacarbonyl and 1,2-ethanedithiol and characterized by in situ Fourier transform infrared spectroscopy, and the resultant material properties are probed by X-ray photoelectron spectroscopy, Raman spectroscopy, and grazing incidence X-ray diffraction. The process exhibits a growth rate of 1.3 Å per cycle, with an ALD/MLD temperature window of 155-175 °C. The hybrid films are moderately stable for about a week in ambient conditions, smooth (σ RMS ≈ 5 Å for films 60 Å thick) and uniform, with densities ranging from 2.2-2.5 g cm −3 . The material is both optically transparent and catalytically active for the hydrogen evolution reaction (HER), with an overpotential (294 mV at −10 mA cm −2 ) superior to that of planar MoS 2 . The enhancement in catalytic activity is attributed to the incorporation of organic chains into MoS 2 , which induces a morphological change during electrochemical testing that increases surface area and yields high activity HER catalysts without the need for deliberate nanostructuring.

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. A broad and expanding range of materials can be produced by atomic layer deposition at relatively low temperatures, including both oxides and metals. For many applications of interest, however, it is desirable to grow more tailored and complex materials such as semiconductors with a certain doping, mixed oxides, and metallic alloys. How well such mixed materials can be accomplished with atomic layer deposition requires knowledge of the conditions under which the resulting films will be mixed, solid solutions, or laminated. The growth and lamination of zinc oxide and tin oxide is studied here by means of the extremely surface sensitive technique of low energy ion scattering, combined with bulk composition and thickness determination, and x-ray diffraction. At the low temperatures used for deposition (150 C), there is little evidence for atomic scale mixing even with the smallest possible bilayer period, and instead a morphology with small ZnO inclusions in a SnO x matrix is deduced. Postannealing of such laminates above 400 C however produces a stable surface phase with a 30% increased density. From the surface stoichiometry, this is likely the inverted spinel of zinc stannate, Zn 2 SnO 4 . Annealing to 800 C results in films containing crystalline Zn 2 SnO 4 , or multilayered films of crystalline ZnO, Zn 2 SnO 4 , and SnO 2 phases, depending on the bilayer period.

Hybrid molecular layer deposition (MLD) has significant potential for the creation of ultrathin electrochemically active materials, due to its ability to combine organic and inorganic species to modulate film properties. However, only a limited number of hybrid MLD processes are demonstrated with electrochemically relevant elements, such as manganese. Here, a "manganicone" manganese hybrid MLD chemistry is developed using the precursors bis(ethylcyclopentadienyl)manganese and ethylene glycol. The resulting manganese alkoxide coordination networks are shown to have many interesting properties, including the ability to seamlessly fill high aspect ratio vias and the chemical conversion into manganese carboxylate in air over several hours at room temperature. Linear, self-saturating growth is reported. Importantly, hybrid manganicone films annealed to 480 °C in air demonstrate a greater stability to restructuring during electrochemical testing than their inorganic counterparts grown by atomic layer deposition, without reducing the activity of the reactive sites on the manganese surface. Thus, hybrid manganese films grown by MLD have significant promise for use as catalysts for the oxygen evolution reaction and as electrodes in thin film batteries.