Metal-organic Decomposition Precursor Research Articles

Deposition of metallic silver from versatile amidinate precursors for use in functional materials

Silver (Ag) amidinate metal organic decomposition precursors of the type: [Ag2((ArN)2C(H))2] (Ar = 2,6-dimethylphenyl (1), 2,6-diethylphenyl (2) and 2,6-diisopropylphenyl (3)) have been used for the first time in the deposition of Ag films on glass with multiple functionalities with potential application in optical/biological sensors or for use in electronic circuitry. Precursors 1–3 were isolated from the reaction of silver acetate with the appropriate ligand in a 1:2 stoichiometry and were characterized by 1H and 13C{1H} NMR, thermal gravimetric analysis and single crystal X-ray diffraction for 2. Single-layer depositions at 200 °C on glass substrates via spin coating produced transparent (>90% transmittance) coatings, with well-defined Ag nanoparticles. Multi-layer depositions at 200 °C on glass had a metallic lustre and were found to be conductive ( ρ = 0.916–1.83 × 10−6 Ωm). All films were strongly adhered and displayed excellent coverage of the substrate. Ag films deposited from 1 to 3 were analysed by grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, energy-dispersive X-ray analysis and scanning electron microscopy, with optical properties determined by UV-Vis spectroscopy.

Fabrication of Single-Phase Manganese Oxide Films by Metal-Organic Decomposition.

Here, single-phase Mn2O3 and Mn3O4 films are successfully fabricated by a facile solution process based on metal-organic decomposition (MOD), for the first time. A formulated manganese 2-ethylhexanoate solution was used as an MOD precursor for the preparation of manganese oxide films. The difference in thermal decomposition behavior of precursor solution in air and inert atmospheres was observed, indicating that the calcination atmosphere is the main factor for controlling the valence of manganese oxide films. Significantly, the solution-coated films on substrates are found to be transformed into single-phase Mn2O3 and Mn3O4 films when they are calcinated under air and inert atmosphere, respectively. The film crystallinity was improved with increasing calcination temperature for both Mn2O3 and Mn3O4 films. In particular, it is noted that the grains of Mn2O3 film were somewhat linearly grown in air, while those of Mn3O4 film exhibited the drastic growth in Ar with an increase of calcination temperature.

Low-Temperature Deposition of Highly Conductive Aluminum Metal Films on Flexible Substrates Using Liquid Alane MOD Precursors.

Metal–organic decomposition (MOD) precursor inks are emerging as the new route to low-temperature deposition of highly conductive metals, owing to the tunability of their decomposition. New methods of printing are being investigated to help negate the progressive issues of the electronics industry, not least the movement toward low-cost polymers and paper substrates. Informed precursor design is crucial if achieving materials capable of this is possible. In this work, the liquid MOD precursors, dimethylethylamine alane (DMEAA) and trimethylamine alane (TEAA), have been used to deposit a highly conductive aluminum (Al) metal with resistivities in the range of 4.10 × 10–5 to 5.32 × 10–7 Ω m (mean electrical resistivity of 8 × 10–6 Ω m, approximately 300 times more resistive than bulk Al metal), without the need for an additional solvent, at low temperatures (100 and 120 °C), on a range of substrates including glass, polyimide, polyethylene terephthalate, and paper. Conductive coatings have been analyzed using X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and resistivity measurements; as a proof of concept, Al deposited on paper has been used in an electrical circuit. Results indicate that DMEAA is a better precursor, producing more conductive films, which is explained by its lower decomposition temperature and higher Al weight loading, indicating potential for significant industrial application.

Formulation of Screen-Printable Cu Molecular Ink for Conductive/Flexible/Solderable Cu Traces.

Screen printing is the most common method used for the production of printed electronics. Formulating copper (Cu) inks that yield conductive fine features with oxidation and mechanical robustness on low-temperature substrates will open up opportunities to fabricate cost-effective devices. We have formulated a screen-printable Cu metal-organic decomposition (MOD) ink comprising Cu formate coordinated to 3-(diethylamino)-1,2-propanediol, a fractional amount of Cu nanoparticles (CuNPs), and a binder. This simple formulation enables ∼70-550 μm trace widths with excellent electrical [∼8-15 mΩ/□/mil or 20-38 μΩ·cm] and mechanical properties with submicron-thick traces obtained by intense pulse light (IPL) sintering on Kapton and poly(ethylene terephthalate) (PET) substrates. These traces are mechanically robust to flexing and creasing where less than 10% change in resistance is observed on Kapton and ∼20% change is observed on PET. Solderable Cu traces were obtained only with the combination of the Cu MOD precursor, CuNP, and polymer binder. Both thermally and IPL sintered traces showed shelf stability (<10% change in resistance) of over a month in ambient conditions and 10-70% relative humidity, suitable for day-to-day fabrication. To demonstrate utility, light-emitting diodes (LEDs) were directly soldered to IPL sintered Cu traces in a reflow oven without the need for a precious metal interlayer. The LEDs were functional not only during bending and creasing of the Cu traces but even after 180 min at 140 °C in ambient air without losing illumination intensity. High definition television antennas printed on Kapton and PET were found to perform well in the ultrahigh frequency region. Lastly, single-walled carbon nanotube-based thin-film transistors on a silicon wafer were fabricated with a screen-printed Cu source and drain electrodes, which performed comparably to silver electrodes with mobility values of 12-15 cm2 V-1 s-1 and current on/off ratios of ∼105 and as effective ammonia sensors providing parts per billion-level detection.

Preparation of (La1 − xSrx)MnO3 − δ thin films on Si (100) substrates by a metal-organic decomposition method for smart radiation devices

(La1−xSrx)MnO3−δ (LSMO) thin films were prepared on Si(100) substrates using a metal-organic decomposition (MOD) technique for smart radiation devices used for thermal control in spacecraft. The 6wt% concentration MOD precursor solutions were spin-coated on Si substrates. The coated films were dried at 90°C and pyrolytically decomposed at 530°C. Finally, they were annealed in air at 750°C to obtain dense, polycrystalline, and single-phase perovskite LSMO films. A ferromagnetic-paramagnetic phase transition was observed close to room temperature in a LSMO film. The thermal emittance of the film was changed as a result of this phase transition. The phase transition temperature increased with an increasing Sr ratio at the A-site of the LSMO and decreased after annealing under a reduced atmosphere. Based on this result, we propose that the temperature range where the thermal emittance is widely variable can be finely tuned on demand with post-annealing.

Atmospheric pressure synthesis of In2Se3, Cu2Se, and CuInSe2 without external selenization from solution precursors

In2Se3, Cu2Se, and CuInSe2 thin films have been successfully fabricated using novel metal organic decomposition (MOD) precursors and atmospheric pressure-based deposition and processing. The phase evolution of the binary (In-Se and Cu-Se) and ternary (Cu-In-Se) MOD precursor films was examined during processing to evaluate the nature of the phase and composition changes. The In-Se binary precursor exhibits two specific phase regimes: (i) a cubic-InxSey phase at processing temperatures between 300 and 400 °C and (ii) the γ-In2Se3 phase for films annealed above 450 °C. Both phases exhibit a composition of 40 at.% indium and 60 at.% selenium. The binary Cu-Se precursor films show more diverse phase behavior, and within a narrow temperature processing range a number of Cu-Se phases, including CuSe2, CuSe, and Cu2Se, can be produced and stabilized. The ternary Cu-In-Se precursor can be used to produce relatively dense CuInSe2 films at temperatures between 300 and 500 °C. Layering the binary precursors together has provided an approach to producing CuInSe2 thin films; however, the morphology of the layered binary structure exhibits a significant degree of porosity. An alternative method of layering was explored where the Cu-Se binary was layered on top of an existing indium-gallium-selenide layer and processed. This method produced highly dense and large-grained (&gt;3 µm) CuInSe2 thin films. This has significant potential as a manufacturable route to CIGS-based solar cells.

A New Ferroelectric Varactor From Water Based Inorganic Precursors

AbstractSolution deposition processes for the production of thin multi-element metal oxide films continue with great interest and varied success. Solution deposition via either sol-gel or MOD (Metal Organic Decomposition) methods are of interest due to the ability to produce a wide variety of compositional products at low capital investment cost. The sol-gel method generally uses hydrolytically sensitive metal alkoxides as the starting materials. Manipulation of the reagents and different hydrolysis rates for multi-element mixtures are issues. The MOD method utilizes large organic acid metal salts as the starting materials. In general, MOD solutions are more hydrolytically stable than the sol-gel solutions. MOD process challenges include large quantities of carbon to be decomposed during the firing, shrinkage and stress of the thin films, variable chemistry in synthesis of the starting materials (especially when the starting materials for the MOD precursors are metal alkoxides), and long reaction times for the synthesis. For both the sol-gel and MOD precursors, toxic and volatile organic chemical (VOC's) solvents are employed as the vehicle.This paper will review the chemistry-related issues to production of consistent highquality metal oxide films via the MOD process. The fabrication of thin BaxSr(1-x)TiO3 (BST) films is described. A new class of MOD precursor has been implemented using polyether acids as the organic vehicle. These new materials are both water stable and water soluble. High quality BST thin films made from these precursors are described and capacitors made from these films are compared to the aliphatic acid MOD materials. Improved capacitors using lower resistance electrodes and interconnects are described, as well as devices designed specifically for our specific application.

Synthesis of water soluble precursors for ferroelectric materials

Solution deposition processes for the production of thin multi-element metal oxide films continue with great interest and varied success. Solution deposition via either sol-gel or MOD (Metal Organic Decomposition) methods are of interest due to the ability to produce a wide variety of compositional products at low capital investment cost. The sol-gel method generally uses hydrolytically sensitive metal alkoxides as the starting materials. Manipulation of the reagents and different hydrolysis rates for multi-element mixtures are issues. The MOD method utilizes large organic acid metal salts as the starting materials. In general, MOD solutions are more hydrolytically stable than the sol-gel solutions. MOD process challenges include large quantities of carbon to be decomposed during the firing, variable chemistry in synthesis of the starting materials (especially when the starting materials for the MOD precursors are metal alkoxides), and long reaction times for the synthesis. For both the current state of the art sol-gel and MOD precursors, toxic and volatile solvents are employed as the vehicle. This paper will review the chemistry related issues to production of consistent high quality metal oxide films via the MOD process. The solid solution BaxSr(1-x)TiO3 will be used as an example. A new technique to quickly obtain controlled carbon content MOD precursor solutions from available starting materials is described. Several new water stable and water soluble BST precursors are described. Details of the electrical properties of capacitors made from the new water based precursors are shown.