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This work introduces oxidative molecular layer deposition (oMLD) as a chemical route to synthesize highly conductive and conformal poly­(3,4-ethylenedioxythiophene) (PEDOT) thin films via sequential vapor exposures of molybdenum­(V) chloride (MoCl5, oxidant) and ethylene dioxythiophene (EDOT, monomer) precursors. The growth temperature strongly affects PEDOT’s crystalline structure and electronic conductivity. Films deposited at ∼150 °C exhibit a highly textured crystalline structure, with {010} planes aligned parallel with the substrate. Electrical conductivity of these textured films is routinely above 1000 S cm–1, with the most conductive films exceeding 3000 S cm–1. At lower temperatures (∼100 °C) the films exhibit a random polycrystalline structure and display smaller conductivities. Compared with typical electrochemical, solution-based, and chemical vapor deposition techniques, oMLD PEDOT films achieve high conductivity without the need for additives or postdeposition treatments. Moreover, the sequential-reaction synthesis method produces highly conformal coatings over high aspect ratio structures, making it attractive for many device applications.

Titanium dioxide atomic layer deposition (ALD) is shown to proceed selectively on oxidized surfaces with minimal deposition on hydrogen-terminated silicon using titanium tetrachloride (TiCl4) and titanium tetra-isopropoxide [Ti(OCH(CH3)2)4, TTIP] precursors. Ex situ x-ray photoelectron spectroscopy shows a more rapid ALD nucleation rate on both Si–OH and Si–H surfaces when water is the oxygen source. Eliminating water delays the oxidation of the hydrogen-terminated silicon, thereby impeding TiO2 film growth. For deposition at 170 °C, the authors achieve ∼2 nm of TiO2 on SiO2 before substantial growth takes place on Si–H. On both Si–H and Si–OH, the surface reactions proceed during the first few TiCl4/TTIP ALD exposure steps where the resulting products act to impede subsequent growth, especially on Si–H surfaces. Insight from this work helps expand understanding of “inherent” substrate selective ALD, where native differences in substrate surface reaction chemistry are used to promote desired selective-area growth.

Area-selective thin film deposition is expected to be important in achieving sub-10 nm semiconductor devices, enabling feature patterning, alignment to underlying structures, and edge definition. Atomic layer deposition (ALD) offers advantages over common chemical vapor deposition methods, such as precise thickness control and excellent conformality. Furthermore, several ALD processes show inherent propensity for substrate-dependent nucleation. For example, tungsten ALD using SiH 4 (or Si 2 H 6 ) and WF 6 is more energetically favorable on Si than on SiO 2 , but selectivity is often lost after several ALD cycles. We show that modifying the W ALD process chemistry can decrease the W nucleation rate on SiO 2 , thereby expanding the ALD "selectivity window". Specifically, we find that adding H 2 during the WF 6 dose step helps passivate SiO 2 against W nucleation without modifying W growth on silicon. Surface characterization confirms that H 2 promotes fluorine passivation of SiO 2 , likely through surface reactions with HF produced in the gas phase. This passivation affords at least 10 additional W ALD cycles, corresponding to ∼6 nm of additional W growth, before substantial nucleation occurs on SiO 2 . We show that reactant modification also reduces undesirable nucleation due to substrate proximity or loading effects in patterned film growth. Further understanding of ALD reaction chemistry and film nucleation will lead to improved selective metal and dielectric film deposition, enabling ALD bottom-up patterning.

While metal‐organic frameworks (MOFs) show great potential for gas adsorption and storage, their powder form limits deployment opportunities. Integration of MOFs on polymeric fibrous scaffolds will enable new applications in gas adsorption, membrane separation, catalysis, and toxic gas sensing. Here, we demonstrate a new synthesis route for growing MOFs on fibrous materials that achieves high MOF loadings, large surface areas and high adsorptive capacities. We find that a nanoscale coating of Al2O3 formed by atomic layer deposition (ALD) on the surface of nonwoven fiber mats facilitates nucleation of MOFs on the fibers throughout the mat. Functionality of MOFs is fully maintained after integration, and MOF crystals are well attached to the fibers. Breakthrough tests for HKUST‐1 MOFs [Cu3(BTC)2] on ALD‐coated polypropylene fibers reveal NH3 dynamic loadings up to 5.93 ± 0.20 mol/kg(MOF+fiber). Most importantly, this synthetic approach is generally applicable to a wide range of polymer fibers (e.g., PP, PET, cotton) and MOFs (e.g., HKUST‐1, MOF‐74, and UiO‐66).