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Because of their unique structural, chemical, optical, and biological properties, metal phosphate coatings are highly versatile for various applications. Thermodynamically facile and favorable functionalization of phosphate moieties (like orthophosphates, metaphosphates, pyrophosphates, and phosphorus-doped oxides) makes them highly sought-after functional materials as well. Being a sequential self-limiting technique, atomic layer deposition has been used for producing high-quality conformal coatings with sub-nanometer control. In this review, different atomic layer deposition-based strategies used for the deposition of phosphate materials are discussed. The mechanisms underlying those strategies are discussed, highlighting advantages and limitations of specific process chemistries. In a second part, the application of metal phosphates deposited through atomic layer deposition in energy storage and other emerging technologies such as electrocatalysis, biomedical, or luminescence applications are summarized. Next to this, perspectives on untangled knowledge gaps and opportunities for future research are also emphasized. [ABSTRACT FROM AUTHOR]

This work reports on the atomic layer deposition process combining lithium hexamethyl disilazide (LiHMDS) and trimethylphosphate (TMP), and studies the impact of adding a trimethylaluminum (TMA) pulse to this process. When only minute traces of aluminum are incorporated, the deposited layer becomes amorphous instead of crystalline. The TMA–TMP interaction plays a key role in this process and is revealed by time-resolved full-range quadrupole mass spectrometry. It is hypothesized that the interaction of unreacted –OCH3 groups with TMA and the formation of Li4P2O7 units lead to higher growth and structural changes as compared to the phosphate process without TMA. The conformal deposition of lithium-containing phosphates may find applications in modification of electrode–electrolyte interfaces in lithium-ion batteries. This is demonstrated in a half-cell. The amorphous mix of Li4P2O7 and Li3PO4 units in the films grown with TMA benefits the conductive properties of the material: an ionic conductivity of 1.47 ± 0.09 × 10−7 S cm−1 at 30 °C is achieved, with an activation energy 0.58 ± 0.02 eV. [ABSTRACT FROM AUTHOR]

Phosphorous-containing materials are used in a wide array of fields, from energy conversion and storage to heterogeneous catalysis and biomaterials. Among these materials, organic-inorganic metal phosphonate solids and thin films present an interesting option, due to their remarkable thermal and chemical stability. Yet, the synthesis of phosphonate hybrids by vapour phase thin film deposition techniques remains largely unexplored. In this work, we present successful deposition of phosphonate-containing films using dimethyl vinylphosphonate (DMVP) as a phosphonate precursor. Two processes have been studied, being a three-step process comprising alternating exposure to trimethylaluminum (TMA), water (H 2 O) and DMVP (ABC process), and a four-step process with an extra O 3 step following the DMVP pulse (ABCD process). The O 3 treatment is employed for in situ functionalisation of the adsorbed phosphonate precursor, transforming the vinyl group into a carboxylic acid end group. For both processes, good precursor saturation was found, with the ABCD process exhibiting a more stable growth per cycle (0.54-0.38 Å per cycle) in the investigated temperature range (100-250 °C). Phosphonate features were visible in FTIR spectra for both films, with the ABCD films also exhibiting a carboxylate signal. XPS showed a higher P incorporation in the ABCD films deposited at 250 °C, although still moderate (P/Al = 0.27), consistent with an alumina structure with phosphonate inclusions. The film stability upon immersion in water was tested, showing a slow oxidation over the course of a week. Finally, annealing experiments in air demonstrated stable films up to 400 °C.