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A novel atomic layer deposition (ALD) process was developed for fabricating quaternary cobalt oxide (La1-xSrx)CoO3-δ thin films having the eye on future applications of such films in e.g. solid oxide fuel cell cathodes, oxygen separation membranes or thermocouples. The deposition parameters and the conditions of a subsequent annealing step were systematically investigated, and using the thus optimized parameters the cation stoichiometry in the films could be accurately tuned. The most detailed study was conducted for x = 0.7, i.e. the composition with the highest application potential within the (La1-xSrx)CoO3-δ system.

Atomic layer deposition (ALD) is widely in use for depositing a variety of materials, such as metal oxides, metal nitrides and metals, in a conformal and defect-free form at low temperatures on high aspect-ratio substrates. These advantages make ALD uniquely powerful method for applications where sensitive substrate materials combine with extreme demands on coating quality and temperature/chemical resistance, such as those often seen in the medical applications.

Implantable medical devices must withstand the corrosive environment inside the human body for prolonged periods of time. Hermetic sealing of the device to protect it from the corrosive environment of human body and vice versa is a key step to enable long life time for the smart medical devices. Atomic layer deposition (ALD) is an advanced deposition technique belonging to the family of chemical vapor deposition (CVD) techniques. In ALD the substrate to be coated is exposed sequentially to precursor chemicals that react with the reactive surface sites on the substrate and form a chemically bonded adsorption layer. This growth mode of the film enables extremely conformal and uniform films to be coated on three-dimensional objects having any shape. Even the smallest, nanometer sized features on the objects can be coated with ease, making the technique extremely useful when hermetic sealing of complex shaped objects are required. The advantages of ALD over other deposition techniques makes it powerful method for applications where sensitive substrate materials combine with extreme demands on coating quality and temperature/chemical resistance, such as those often seen in the medical applications. In order to make a robust protective sealing for the medical device, the film properties must fulfill certain key criteria. First and foremost, the film material needs to be non-toxic for human cells in order to be biocompatible. Secondly, the film needs to function as an highly efficient diffusion barrier against the ions and molecules present in body fluids. In addition, the adhesion of the film with the device surface needs to be strong enough to prevent the delamination of the film. In our recent work [1] we have shown that SiO2-HfO2 coated sub-millimeter-sized microelectronic chiplets for wireless body implants can last without degradation and electronic failure in accelerated aging tests in saline at T = 87 °C for more than 180 days. This corresponds an equivalent lifetime of more than 10 years at human body equivalent temperature of 37 °C. Latest results on ALD films (deposited with Picosun® R-200 Advanced ALD reactor) for medical applications will also be discussed. Biocompatibility tests for Al2O3, TiO2, HfO2, SiO2, Ta2O5 films using the ISO standard Cytotoxicity of Medical Device (ISO 10993-5) procedure will be presented. In addition, we will show results of corrosion tests in PBS solution at elevated temperature (87 °C) for a number of ALD oxides and their nanolaminates, highlighting a stress control method that can improve the long-term delamination resistance of the coatings. Furthermore, we will show some results on the diffusion barrier properties of Al2O3, TiO2, HfO2, SiO2, Ta2O5 and their nanolaminates on different electrode materials (Al, Au, Pt, TiN) when exposed to PBS solution. [1] Conformal Hermetic Sealing of Wireless Microelectronic Implantable Chiplets by Multilayered Atomic Layer Deposition (ALD) by J. Jeong, F. Laiwalla, J. Lee, R. Ritasalo, M. Pudas, L. Larson, V. Leung, and A. Nurmikko, https://doi.org/10.1002/adfm.201806440. Acknowledgements: This work is part of the ULIMPIA project funded by PENTA under grant number PENTA-2017-Call2-16101-ULIMPIA

Novel atomic layer deposition (ALD) process to deposit high-quality SrCoO3−δ thin films is introduced. Linear film growth is demonstrated within the film-thickness range of 15–300 nm. Post-annealing at 600 °C (in O2 or N2 atmosphere) is required to crystallize the as-deposited amorphous films. The new ALD process produces SrCoO3−δ films with a precisely controlled cation stoichiometry (±2.5%) and an appreciably high growth rate (1.67 A per supercycle), hence providing us with a prominent method of fabricating high-quality SrCoO3−δ thin films in a readily scalable manner e.g. for intermediate-temperature solid oxide fuel cell cathodes.

Here a novel water-containing derivative phase (with the elongated c axis from 20.2 to 28.0 A) is reported for the n = 2 member of the Srn+1FenO3n+1-δ Ruddlesden−Popper series, i.e., Sr3Fe2O7-δ with the layer sequence of SrO−SrO−FeO2−SrO1-δ−FeO2. The intercalated water molecules in the derivative phase are believed to reside within the (SrO)2 double-layer block, probably accompanied by additional protons. The latter belief is supported by the fact that upon water incorporation iron was found to be reduced (toward the trivalent state). High-quality samples of the parent Sr3Fe2O7-δ phase were synthesized from a solution-derived precursor powder. For samples synthesized in air cerimetric titration yielded an oxygen content at 7 − δ = 6.44. More oxygen-deficient samples with 7 − δ = 6.32 and 6.18 were obtained by postannealing the as-synthesized material in flowing Ar gas at 400 and 500 °C, respectively. Independent of the value of δ, all the Sr3Fe2O7-δ samples transformed to the water derivative when subject...

Oxygen stoichiometry in the perovskite system (Ba 0.5 La 0.5 )(Fe 1− x Cu x )O 3− w with x varying in the range of 0 to 1 was studied by thermogravimetry, 57 Fe Mossbauer spectroscopy and different wet-chemical analysis methods. Both the maximum oxygen content and the amount of removable oxygen strongly depended on the copper-to-iron ratio. In this respect the samples containing both copper and iron were nearly identical but differed from the end members of the system. In the samples with 0.1≤ x ≤0.85 the maximum oxygen content varied in the narrow range of w =0.25–0.33 whereas for the x =0 and x =1 samples the values of w =0.06 and 0.60, respectively, were determined. The amount of removable oxygen (Δ w ) was the smallest for the Fe-free sample. It is interesting to note that, the maximum oxygen content of the x =0.5 sample (as well as the samples with 0.15≤ x ≤0.85) was found to continue the trend of decreasing w with increasing RE ion size, as previously observed for the double-perovskite series BaRE(Fe 0.5 Cu 0.5 ) 2 O 5+ δ .