Atomic layer deposition (ALD) processes of noble metals are gaining increasing interest for applications in catalysis and microelectronics. Platinum ALD from (methylcyclopentadienyl)trimethylplatinum (MeCpPtMe3) and O2 gas has been considered as a model system for noble metal ALD. However, many questions about the underlying reaction mechanisms remain. In this work, the insight into the Pt ALD reaction mechanisms is extended by considering the catalytic nature of the Pt film. It is evaluated which surface reactions are likely to take place during Pt ALD on the basis of surface science results on the interaction of the Pt surface with O2 and hydrocarbon species, combined with previously reported Pt ALD mechanistic studies. In analogy to the reactions of hydrocarbon species on catalytic Pt, it is proposed that, in addition to combustion-like reactions, dehydrogenation of precursor ligands plays a role in the mechanism. The formation of CH4 during the MeCpPtMe3 exposure pulse is explained by hydrogenation of methyl species by hydrogen atoms released from dehydrogenation reactions. The implications of the surface reactions on the self-limiting behavior, the growth rate, and the temperature dependence of the process are discussed. Moreover, this work demonstrates that surface science studies are of great use in obtaining more understanding of metal ALD processes.

Control of the nucleation behavior during atomic layer deposition (ALD) of metals is of great importance for the deposition of metallic thin films and nanoparticles, and for nanopatterning applications. In this work it is established for Pt ALD, that the exposure to O2 during the O2 pulse of the ALD process is the key parameter controlling the nucleation behavior. The O2 dependence of the Pt nucleation is explained by the enhanced diffusion of Pt species in the presence of oxygen, and the resulting faster aggregation of Pt atoms in metal clusters that catalyze the surface reactions of ALD growth. Moreover, it is demonstrated that the O2 exposure can be used as the parameter to tune the nucleation to enable (i) deposition of ultrathin films with minimal nucleation delay, (ii) preparation of single element or core/shell nanoparticles, and (iii) nanopatterning of metallic structures based on area-selective deposition.

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. The metalorganic precursor cyclopentadienylethyl͑dicarbonyl͒ruthenium ͑CpRu͑CO͒ 2 Et͒ was used to develop an atomic layer deposition ͑ALD͒ process for ruthenium. O 2 gas and O 2 plasma were employed as reactants. For both processes, thermal and plasma-assisted ALD, a relatively high growth-per-cycle of ϳ1 Å was obtained. The Ru films were dense and polycrystalline, regardless of the reactant, yielding a resistivity of ϳ16 ⍀ cm. The O 2 plasma not only enhanced the Ru nucleation on the TiN substrates but also led to an increased roughness compared to thermal ALD.

Colloidal halide perovskite nanocrystals (NCs) have the possibility of easy scale-up due to their batch synthesis and have demonstrated excellent optoelectronic properties. In particular, perovskite NCs have remarkably high photoluminescence quantum yields in solution and as thin films and impressive open circuit voltages in photovoltaic devices. Despite these promising results, little work has been done to understand the stability of CsPbI 3 NCs for optoelectronic device applications. It has been previously shown that the ligands impart tensile surface strain, which stabilizes the black three-dimensional (3D) perovskite phase against phase degradation, making CsPbI 3 NCs some of the most structurally robust inorganic halide perovskites to date. However, understanding exactly how CsPbI 3 NCs degrade under ambient conditions is critical. We demonstrate that the degradation mechanism of NCs is unique from, and 2 orders of magnitude slower than, their polycrystalline thin-film counterparts. Under specific conditions, CsPbI 3 NC films show a compositional instability instead of the phase instability seen in large grain CsPbI 3 . This is mediated through reactions with superoxide and other reactive oxygen species, which are initiated from surface defect states, O 2 and light. We then use this mechanistic insight to identify multiple strategies to prolong the lifetimes of CsPbI 3 NC films, by going beyond surface strain to mitigate key surface chemistries. We demonstrate that (1) minimizing the number of surface defects (2) using an alkylammonium bromide ligand surface treatment and (3) encapsulation with an oxygen scavenging layer all increase NC film lifetimes by inhibiting various steps in the photo-oxidation degradation reaction.