Two-dimensional
(2-D) metal chalcogenides have received great attention
because of their unique properties, which are different from bulk
materials. A challenge in implementing 2-D metal chalcogenides in
emerging devices is to prepare a well-crystallized layer over large
areas at temperatures compatible with current fabrication processes.
Tin monosulfide, a p-type layered semiconductor with
a high hole mobility, is a promising candidate for realizing large-area
growth at low temperatures because of its low melting point. However,
tin sulfides exist in two notable crystalline phases, SnS and SnS2. Therefore, it is imperative to control the oxidation state
of Sn to achieve a pure SnS film. Here, the synthesis of SnS thin
films by atomic-layer-deposition (ALD) is demonstrated using bis(1-dimethylamino-2-methyl-2-propoxy)tin(II)
and H2S as Sn and S sources, respectively, over a wide
temperature window (90–240 °C). Impurities such as carbon,
oxygen, and nitrogen were negligibly detected. The morphological evolution
of plate-like orthorhombic SnS grains was observed above 210 °C.
Moreover, properties of thin film transistors and gas sensors using
SnS films as the active layers were investigated. The SnS ALD process
would provide promising opportunities to exploit the intriguing properties
of the 2-D metal chalcogenides for realizing emerging electronic devices.
The feasibility of using the thin film technology in utilizing lanthanum strontium manganite (LSM) for a solid oxide fuel cell (SOFC) cathode in a low-temperature regime is investigated in this study. Thin film LSM cathodes were fabricated using pulsed laser deposition (PLD) on anode-supported SOFCs with yttria-stabilized zirconia (YSZ) electrolytes. Although cells with a 1 µmthick LSM cathode showed poor low-temperature cell performance compared to that of a cell with a bulk-processed cathode due to the lack of a triple-phase boundary length, the cell with 200 nm-thick gadolinia-doped ceria (GDC) inserted between the LSM and YSZ showed enhanced performance and more stable operation characteristics in a comparison of a cell without a GDC layer. We postulate that the GDC layer likely improved the cathode adhesion, therefore contributing to the improvement of the cell performance instead of serving as an interfacial reaction buffer.
Hybridization of dense ceramic membranes for hydrogen separation with an electronically conductive metallic phase is normally utilized to enhance the hydrogen permeation flux and thereby to increase the production efficiency of hydrogen. In this study, we developed a nickel and proton conducting oxide (BaCe 0.9 Y 0.1 O 3-δ : BCY) based cermet (ceramic-metal composites) membrane. Focused on the general criteria in that the hydrogen permeation properties of a cermet membrane depend on its microstructural features, such as the grain size and the homogeneity of the mix, we tried to optimize the microstructure of Ni-BCY cermets by controlling the fabrication condition. The Ni-BCY composite powder was synthesized via a solid-state reaction using 2NiCO 3 •3Ni(OH) 2 •4H 2 O, BaCeO 3 , CeO 2 and Y 2 O 3 as a starting material. To optimize the mixing scale and homogeneity of the composite powder, we employed a high-energy milling process. With this high-energy milled composite powder, we could fabricate a fine-grained dense membrane with an excellent level of mixing homogeneity. This controlled Ni-BCY cermet membrane showed higher hydrogen permeability compared to uncontrolled Ni-BCY cermets created with a conventionally ball-milled composite powder.
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