Molecular layer deposition (MLD) of hybrid organic–inorganic thin films called “titanicones” was achieved using tetrakisdimethylaminotitanium (TDMAT) and glycerol (GL) or ethylene glycol (EG) as precursors. For EG, in situ ellipsometry revealed that the film growth initiates, but terminates after only 5 to 10 cycles, probably because both hydroxyls react with the surface. GL has a third hydroxyl group, and in that case steady state growth could be achieved. The GL process displayed self-limiting reactions for both reactants in the temperature range from 80 °C to 160 °C, with growth rates of 0.9 to 0.2 Å per cycle, respectively. Infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the hybrid nature of the films, with a carbon atomic concentration of about 20%. From X-ray reflectivity, the density was estimated at 2.2 g cm⁻³. A series of films was subjected to water etching and annealing under air or He atmosphere at 500 °C. The carbon content of the films was monitored with FTIR and XPS. Almost all carbon was removed from the air annealed and water treated films. The He annealed samples however retained their carbon content. Ellipsometric porosimetry (EP) showed 20% porosity in the water etched samples, but no porosity in the annealed samples. Electrochemical measurements revealed lithium ion activity during cyclic voltammetry in all treated films, while the as-deposited film was inactive. With increasing charge current, the He annealed samples outperformed amorphous and anatase TiO₂ references in terms of capacity retention.

Solar hydrogen devices combine the power of photovoltaics and water electrolysis to produce hydrogen in a hybrid form of energy production. To engineer these into integrated devices (i.e. a water splitting catalyst on top of a PV element), the need exists for thin film catalysts that are both transparent for solar light and efficient in water splitting. Manganese oxides have already been shown to exhibit good water splitting performance, which can be further enhanced by conformal coating on high surface-area structures. The latter can be achieved by atomic layer deposition (ALD). However, to optimize the catalytic and transparency properties of the water splitting layer, an excellent control over the oxidation state of the manganese in the film is required. So far MnO, Mn₃O₄ and MnO₂ ALD have been shown, while Mn₂O₃ is the most promising catalyst. Therefore, we investigated the post-deposition oxidation and reduction of MnO and MnO₂ ALD films, and derived strategies to achieve every phase in the MnO–MnO₂ range by tuning the ALD process and post-ALD annealing conditions. Thin film Mn₂O₃ is obtained by thermal reduction of ALD MnO₂, without the need for oxidative high temperature treatments. The obtained Mn₂O₃ is examined for solar water splitting devices, and compared to the as-deposited MnO₂. Both thin films show oxygen evolution activity and good solar light transmission.

Molecular layer deposition (MLD) of hybrid organic–inorganic thin films called “vanadicones” was investigated using tetrakisethylmethylaminovanadium (TEMAV) as the metal precursor and glycerol (GL) or ethylene glycol (EG) as the organic reactant. Linear and continued growth could only be achieved with GL as the organic reactant. The TEMAV/GL process displayed self-limiting reactions for both precursor and reactant pulses in the temperature range from 80 °C to 180 °C, with growth rates of 1.2 to 0.5 Å per cycle, respectively. Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) revealed the hybrid nature of the films. From X-ray reflectivity, the density was estimated at 2.6 g cm⁻³. A series of 21 nm vanadicone films were subjected to annealing under oxidizing (air) or inert (He) atmospheres at 500 °C. During annealing in air, the film crystallized to the V₂O₅ phase and all carbon was removed from the film. The films annealed in helium remained amorphous and retained most of their carbon content. Electrochemical measurements revealed lithium-ion activity during cyclic voltammetry in all treated films, while the as deposited film was inactive. In the 2.9 to 3.5 V vs. Li⁺/Li potential region, no improvement over the V₂O₅ reference was observed. However, the helium annealed samples outperformed V₂O₅ in terms of capacity, rate performance and cyclability when charged and discharged in the 1.0 to 3.5 V vs. Li⁺/Li region. This result enables the application of V_xO_y-based hybrid electrodes in a wider potential range without sacrificing the stability and performance.