Nanostructures synthesised by hard-templating assisted methods are advantageous as they retain the size and morphology of the host templates which are vital characteristics for their intended ...applications. A number of techniques have been employed to deposit materials inside porous templates, such as electrodeposition, vapour deposition, lithography, melt and solution filling, but most of these efforts have been applied with pore sizes higher in the mesoporous regime or even larger. Here, we explore atomic layer deposition (ALD) as a method for nanostructure deposition into mesoporous hard templates consisting of mesoporous silica films with sub-5 nm pore diameters. The zinc oxide deposited into the films was characterised by small-angle X-ray scattering, X-ray diffraction and energy-dispersive X-ray analysis.
Unencapsulated organo‐tin halide perovskite photovoltaic (PV) devices exhibiting record stability (for organo‐tin perovskite PV devices) when tested under continuous one sun solar illumination in ...ambient air and under electrical load are reported. This exceptional stability is made possible by the use of a bathocuproine | copper cathode in an inverted device architecture. A series of experiments designed to elucidate the underlying reasons for the high stability show that, compared to conventional silver electrodes, compact copper electrodes are far more resistant to corrosion by I2 gas (evolved when organo‐tin halide decomposes) and toward adverse morphological evolution and ingress of oxygen and water molecules through the top electrode into the device. The findings of these experiments show that copper should be the metal of choice for the reflective cathode in inverted tin perovskite PVs when the material interfacing the metal interacts strongly with it, enabling compact film formation and a stable interface toward copper diffusion into the adjacent charge transport layer.
Organo‐tin halide perovskite photovoltaics without encapsulation, tested in ambient air under electrical load exhibit exceptional stability when using a bathocuproine | copper cathode in an inverted device architecture. It is shown that compact copper electrodes are far more resistant to corrosion by iodine gas, toward adverse morphological evolution, and are less permeable to oxygen and water than conventional silver cathodes.
Low temperature ionic conducting materials such as OH
and H
ionic conductors are important electrolytes for electrochemical devices. Here we show the discovery of mixed OH
/H
conduction in ceramic ...materials. SrZr
Y
O
exhibits a high ionic conductivity of approximately 0.01 S cm
at 90 °C in both water and wet air, which has been demonstrated by direct ammonia fuel cells. Neutron diffraction confirms the presence of OD bonds in the lattice of deuterated SrZr
Y
O
. The OH
ionic conduction of CaZr
Y
O
in water was demonstrated by electrolysis of both H
O and D
O. The ionic conductivity of CaZr
Y
O
in 6 M KOH solution is around 0.1 S cm
at 90 °C, 100 times higher than that in pure water, indicating increased OH
ionic conductivity with a higher concentration of feed OH
ions. Density functional theory calculations suggest the diffusion of OH
ions relies on oxygen vacancies and temporarily formed hydrogen bonds. This opens a window to discovering new ceramic ionic conducting materials for near ambient temperature fuel cells, electrolysers and other electrochemical devices.
Abstract Integrating resistive memory or neuromorphic memristors into mainstream silicon technology can be substantially facilitated if the memories are built in the back-end-of-line (BEOL) and ...stacked directly above the logic circuitries. Here we report a promising memristor employing a plasma-enhanced chemical vapour deposition (PECVD) bilayer of amorphous SiC/Si as device layer and Cu as an active electrode. Its endurance exceeds one billion cycles with an ON/OFF ratio of ca. two orders of magnitude. Resistance drift is observed in the first 200 million cycles, after which the devices settle with a coefficient of variation of ca. 10% for both the low and high resistance states. Ohmic conduction in the low resistance state is attributed to the formation of Cu conductive filaments inside the bilayer structure, where the nanoscale grain boundaries in the Si layer provide the pre-defined pathway for Cu ion migration. Rupture of the conductive filament leads to current conduction dominated by reverse bias Schottky emission. Multistate switching is achieved by precisely controlling the pulse conditions for potential neuromorphic computing applications. The PECVD deposition method employed here has been frequently used to deposit typical BEOL SiOC low-k interlayer dielectrics. This makes it a unique memristor system with great potential for integration.
An effective approach is reported to enhance the stability of inverted organo‐tin halide perovskite photovoltaics based on capping the cathode with a thin layer of bismuth. Using this simple ...approach, unencapsulated devices retain up to 70% of their peak power conversion efficiency after up to 100 h testing under continuous one sun solar illumination in ambient air and under electrical load, which is exceptional stability for an unencapsulated organo‐tin halide perovskite photovoltaic device tested in ambient air. The bismuth capping layer is shown to have two functions: First, it blocks corrosion of the metal cathode by iodine gas formed when those parts of the perovskite layer not protected by the cathode degrade. Second, it sequesters iodine gas by seeding its deposition on top of the bismuth capping layer, thereby keeping it away from the electro‐active parts of the device. The high affinity of iodine for bismuth is shown to correlate with the high polarizability of bismuth and the prevalence of the (012) crystal face at its surface. Bismuth is ideal for this purpose, because it is environmentally benign, non‐toxic, stable, cheap, and can be deposited by simple thermal evaporation at low temperature immediately after deposition of the cathode.
Unencapsulated inverted organo‐tin halide perovskite photovoltaics using a bismuth capped copper cathode achieve record stability when tested in ambient air under 1 sun simulated solar illumination and electrical load. The bismuth layer blocks corrosion of the copper electrode by iodine gas and sequesters iodine gas by seeding its condensation on top of the device.
The hetero‐epitaxy of (112‾2) GaN on (101‾0) sapphire was optimized in metal–organic vapor phase epitaxy. Best results were obtained from an AlN nucleation followed by AlN and AlGaN layers, and ...inserting low‐temperature AlN interlayers (ILs) as well as a SiNx IL. X‐ray diffraction (XRD) of ω scans of the symmetric (112‾2) reflection yielded an ω FWHM <450″ along 112‾3‾ and <900″ along 101‾0 together with a 100×100μm2 rms roughness below 10 nm as determined by atomic force microscopy. The lowest threading dislocation density achieved was ≈109cm−2 while the basal plane stacking fault density was in the lower 105cm−1 range as determined by transmission electron microscopy. The suppression of the unwanted (101‾3‾) phase was lower than 1 in 10,000 as judged from XRD.
Josephson junctions based on InAs semiconducting nanowires and Nb superconducting electrodes are fabricated in situ by a special shadow evaporation scheme for the superconductor electrode. Compared ...to other metallic superconductors such as Al, Nb has the advantage of a larger superconducting gap which allows operation at higher temperatures and magnetic fields. Our junctions are fabricated by shadow evaporation of Nb on pairs of InAs nanowires grown selectively on two adjacent tilted Si (111) facets and crossing each other at a small distance. The upper wire relative to the deposition source acts as a shadow mask determining the gap of the superconducting electrodes on the lower nanowire. Electron microscopy measurements show that the fully in situ fabrication method gives a clean InAs/Nb interface. A clear Josephson supercurrent is observed in the current–voltage characteristics, which can be controlled by a bottom gate. The large excess current indicates a high junction transparency. Under microwave radiation, pronounced integer Shapiro steps are observed suggesting a sinusoidal current–phase relation. Owing to the large critical field of Nb, the Josephson supercurrent can be maintained to magnetic fields exceeding 1 T. Our results show that in situ prepared Nb/InAs nanowire contacts are very interesting candidates for superconducting quantum circuits requiring large magnetic fields.
Cation (Sm3+) and anion (N3−) co-doped CeO2 (oxynitride) with anion (oxygen and nitrogen) vacancies can significantly improve the stability and activity of low-cost Fe catalyst for efficient ...synthesis of ammonia.
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•For the first time, cation doped oxynitride solid solution is synthesised.•The nitrogen vacancies have better size match with adsorbed nitrogen.•High mobility of anion vacancies may facilitate the NH3 synthesis reaction.•The apparent activation energy of Fe- Ce0.5Sm0.5O2-xNy is around of 45 kJ mol−1.•Ce0.5Sm0.5O2-xNy improves the activity and stability of Fe catalyst for NH3 synthesis.
For the first time, new Sm doped cerium oxynitrides with the formula Ce1-zSmzO2-xNy (z ≤ 0.5) are synthesized in order to maximize the concentration of anion vacancies. Single phase Sm-doped CeO2-xNy were confirmed by XRD, HRTEM and Rietveld refinement. These oxynitrides show a great promotion effect for the low-cost Fe catalyst for the ammonia synthesis. At 350 °C and 1 MPa, the activity of 80 wt% Fe- 20 wt% Ce1-zSmzO2xNy is one of the highest reported for non-Ru catalysts for the Haber-Bosch reaction. The apparent activation energy of the 80 wt% Fe- 20 wt% Ce1-zSmzO2xNy catalysts with z ≥ 0.3 is around 45 kJ/mol, which is in the lowest range among all reported ammonia synthesis catalysts. Introduction of nitrogen vacancies through doping may facilitate the mobility of nitrogen vacancies. This study demonstrates doped oxynitrides with a large concentration of anion vacancies, particularly nitrogen vacancies are excellent promoters/co-catalysts for ammonia synthesis.
The binary diffusion coefficients of arachidonic acid ethyl esthers (AA-EE), cis-5,8,11,14,17-eicosapentaenoic acid ethyl esters (EPA-EE), and cis-4,7,10,13,16,19-docosahexaenoic acid ethyl esthers ...(DHA-EE) in supercritical carbon dioxide were measured at temperatures from 308.15 K to 338.15 K and pressures from 8.42 MPa to 29.95 MPa by the Taylor−Aris capillary peak broadening method. The obtained diffusion coefficients are in the range of (5.54 × 10-5) cm2·s-1 to (13.8 × 10-5) cm2·s-1 with small differences between AA-EE, EPA-EE, and DHA-EE. The measured D 12 values were fitted with absolute average deviations of less than 2 % by three predictive models: Scheibel, Catchpole−King, and He−Yu−Su.
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