Interphase formation with carboxylic acids as slurry additives for Si electrodes in Li-ion batteries. Part 2: a photoelectron spectroscopy study

The mass loading of Si–graphite electrodes is often considered as a parameter of secondary importance when testing their electrochemical performance. However, if a sacrificial additive is present in the electrolyte to improve the electrochemical performance, the electrode loading becomes the battery cycle-life-determining factor. The correlation between mass-loading, electrolyte additive, and binder type was investigated by analyzing the cycling behavior of Si–graphite electrodes, prepared with water-based binders, with mass loading ranging from 3 to 9.5 mg cm-2 and cycled with FEC electrolyte additive, while keeping electrolyte amount constant. A lower loading was obtained by keeping slurry preparation steps unchanged from binder to binder and resulted in a longer lifetime for some of the binders. When the final loading was kept constant instead, the performance became independent of the binder used. Because such results can lead to the misinterpretation of the influence of electrode components on the cycling stability (and to a preference of one binder over another in our case), we propose that a comparison of long-term electrochemical performance data of Si–graphite electrodes needs to be always collected by using the same mass-loading with the constant electrolyte and additive

Thin film structural analysis using variable-period x-ray standing waves

Variable-period x-ray standing wave (VPXSW) studies have been carried out using 3 keV x rays and photoelectron detection. Two model surfaces have been used, a native SiO2 layer (20 Å thick) on bulk silicon, and a purpose-built multilayer surface comprising a chloroform/water marker layer (12 Å thick) on an ionic liquid spacer layer (211 Å thick) deposited on a SiO2/Si substrate at 90 K. By using photoelectron detection, both chemical and elemental sensitivity were achieved. The surfaces were modeled using dynamic x-ray scattering for x-ray intensity, and attenuation of photoelectrons transmitted through the layers, to produce simulations which accurately reproduced the experimental VPXSW measurements. VPXSW measurements made using the substrate, spacer layer, and marker layer photoelectron signatures produced consistent structural values. This work demonstrates that VPXSW can be used to determine chemically specific layer thicknesses within thick (≲300Å) surface structures composed of the light elements B, C, N, O, F, and Cl with an accuracy of 10 to 15 Å, perpendicular to the surface

Capturing the Dynamics of Ti Diffusion Across Ti _x W _1−x /Cu Heterostructures using X‐Ray Photoelectron Spectroscopy

Interdiffusion phenomena between adjacent materials are highly prevalent in semiconductor device architectures and can present a major reliability challenge for the industry. To fully capture these phenomena, experimental approaches must go beyond static and post-mortem studies to include in situ and in-operando setups. Here, soft and hard X-ray photoelectron spectroscopy (SXPS and HAXPES) is used to monitor diffusion in real-time across a proxy device. The device consists of a Si/SiO2/TixW1−x(300 nm)/Cu(25 nm) thin film material stack, with the TixW1−x film (x = 0.054, 0.115, 0.148) acting as a diffusion barrier between Si and Cu. The interdiffusion is monitored through the continuous collection of spectra whilst in situ annealing to 673 K. Ti within the TiW is found to be highly mobile during annealing, diffusing out of the barrier and accumulating at the Cu surface. Increasing the Ti concentration within the TixW1−x film increases the quantity of accumulated Ti, and Ti is first detected at the Cu surface at temperatures as low as 550 K. Surprisingly, at low Ti concentrations (x = 0.054), W is also mobile and diffuses alongside Ti. By monitoring the Ti 1s core level with HAXPES, the surface-accumulated Ti was observed to undergo oxidation even under ultra-high vacuum conditions, highlighting the reactivity of Ti in this system. These results provide crucial evidence for the importance of diffusion barrier composition on their efficacy during device application, delivering insights into the mechanisms underlying their effectiveness and limitations

On the optical properties of Ag^{+15} ion-beam irradiated TiO_{2} and SnO_{2} thin films

The effects of 200-MeV Ag^{+15} ion irradiation on the optical properties of TiO_{2} and SnO_{2} thin films prepared by using the RF magnetron sputtering technique were investigated. These films were characterized by using UV-vis spectroscopy, and with increasing irradiation fluence, the transmittance for the TiO_{2} films was observed to increase systematically while that for SnO_{2} was observed to decrease. Absorption spectra of the irradiated samples showed minor changes in the indirect bandgap from 3.44 to 3.59 eV with increasing irradiation fluence for TiO_{2} while significant changes in the direct bandgap from 3.92 to 3.6 eV were observed for SnO_{2}. The observed modifications in the optical properties of both the TiO_{2} and the SnO_{2} systems with irradiation can be attributed to controlled structural disorder/defects in the system.Comment: 6 pages, ICAMD-201

Systematic review on applicability of magnetic iron-oxides integrated photocatalysts for degradation of organic pollutants in water

Owing to biocompatibility, abundance, and low cost, magnetic iron oxides are well suited for the design of efficient and magnetically separable photocatalysts for water treatment. This review presents a detailed survey of magnetic iron oxide–integrated photocatalysts (MIOIPs), in which we have discussed essential conditions needed for designing of efficient MIOIPs for water purification. The synthesis methods and detailed experimental setups for fabrication of MIOIPs were discussed, and the integration manners of iron oxides (Fe2O3, Fe3O4, FeO, and ferrites) with binary, ternary, and quaternary non-magnetic photocatalysts have been categorized. The mechanistic view of enhanced photocatalytic activity caused by different MIOIPs under various light sources was also elaborately argued. The role of various reactive species in photocatalytic oxidative degrading of organic pollutants was investigated. Altogether, this review article has compressively considered and discussed various signs of advancements made toward the synthesis of MIOIPs and their stability, recyclability, and catalytic efficacy for wastewater treatment

Design and realization of topological {Dirac} fermions on a triangular lattice

Large-gap quantum spin Hall insulators are promising materials for room-temperature applications based on Dirac fermions. Key to engineer the topologically non-trivial band ordering and sizable band gaps is strong spin-orbit interaction. Following Kane and Mele’s original suggestion, one approach is to synthesize monolayers of heavy atoms with honeycomb coordination accommodated on templates with hexagonal symmetry. Yet, in the majority of cases, this recipe leads to triangular lattices, typically hosting metals or trivial insulators. Here, we conceive and realize “indenene”, a triangular monolayer of indium on SiC exhibiting non-trivial valley physics driven by local spin-orbit coupling, which prevails over inversion-symmetry breaking terms. By means of tunneling microscopy of the 2D bulk we identify the quantum spin Hall phase of this triangular lattice and unveil how a hidden honeycomb connectivity emerges from interference patterns in Bloch px ± ipy-derived wave functions

Synthesis of Eu3+−doped ZnO/Bi2O3 heterojunction photocatalyst on graphene oxide sheets for visible light-assisted degradation of 2,4-dimethyl phenol and bacteria killing

We reported the immobilization of binary heterojunction Eu3+-ZnO/Bi2O3 over the surface of graphene oxide (GO) sheets by precipitation method to compose a visible light drive photocatalyst. The ternary nanocomposites were characterized by different spectral technique like FESEM, FTIR, XRD, XPS, EDX, HRTEM, UV–visible, PL, HPLC and LCMS analysis. The high specific surface area of 106.0 m2g-1 of Eu3+-ZnO/Bi2O3/GO nanocomposites was ascertained by BET adsorption-desorption isotherm. The nano-composite exhibit excellent photo-efficiency for the photodegradation of 2, 4-dimethyl phenol (DMP) under visible region and was almost completely mineralized in 100 min as compared to the bare and binary system. The mineralized products of DMP were analyzed by HPLC and LCMS analysis. The kinetic model suggests the degradation pathway obeys pseudo-first order kinetic. Their antibacterial property were assessed against E. coli bacteria and nearly 90% of gram negative bacteria were killed by using ternary photocatalyst as determined by CFU method. Also, Eu3+-ZnO/Bi2O3/GO nanocomposites possessed significant recycle efficiency up to six consecutive cycles which is beneficial to minimize the tariff. The improved photo-efficiency is due to the extension towards visible region, increase surface area, and high charge separation in ternary heterojunction

Direct quantitative identification of the "surface trans-effect"

The strong parallels between coordination chemistry and adsorption on metal surfaces, with molecules and ligands forming local bonds to individual atoms within a metal surface, have been established over many years of study. The recently proposed "surface trans-effect" (STE) appears to be a further manifestation of this analogous behaviour, but so far the true nature of the modified molecule-metal surface bonding has been unclear. The STE could play an important role in determining the reactivities of surface-supported metal-organic complexes, influencing the design of systems for future applications. However, the current understanding of this effect is incomplete and lacks reliable structural parameters with which to benchmark theoretical calculations. Using X-ray standing waves, we demonstrate that ligation of ammonia and water to iron phthalocyanine (FePc) on Ag(111) increases the adsorption height of the central Fe atom; dispersion corrected density functional theory calculations accurately model this structural effect. The calculated charge redistribution in the FePc/H2O electronic structure induced by adsorption shows an accumulation of charge along the σ-bonding direction between the surface, the Fe atom and the water molecule, similar to the redistribution caused by ammonia. This apparent σ-donor nature of the observed STE on Ag(111) is shown to involve bonding to the delocalised metal surface electrons rather than local bonding to one or more surface atoms, thus indicating that this is a true surface trans-effect

Coupling of single, double, and triple-decker metal-phthalocyanine complexes to ferromagnetic and antiferromagnetic substrates

We report a survey of the magnetic properties of metal-organic complexes coupled to ferromagnetic and antiferromagnetic surfaces. Using element-resolved X-ray magnetic circular dichroism, we investigate the magnetism of single, double, and triple-decker phthalocyanines focusing on MnPc, TbPc, and TbPc deposited on Ni, Mn, and CoO thin films. Depending on the number of Pc ligands, we find that the metal ions within the molecules couple either parallel or antiparallel to a ferromagnetic substrate. Whereas single-decker complexes such as MnPc form a unique magnetic entity with ferromagnetic films, the intrinsic single molecule magnet properties of TbPc and TbPc remain largely unaltered. TbPc deposited on perpendicularly magnetized Ni films exhibits enhanced magnetic stability compared to TbPc in molecular crystals, opposite to TbPc deposited on in-plane magnetized Ni. Depending on the competition between uniaxial anisotropy, superexchange, and Zeeman interaction, the magnetic moment of TbPc can be aligned parallel or antiparallel to that of the substrate by modulating the intensity of an external magnetic field. This occurs also for TbPc, but the substrate-induced exchange coupling in triple-decker molecules is found to be short-ranged, that is, limited to the Tb ion closer to the ferromagnetic surface. Finally, we discuss the conditions required to establish exchange bias between molecules and antiferromagnetic substrates. We show that TbPc deposited on antiferromagnetic Mn thin films exhibits both exchange bias and enhanced coercivity when field cooled parallel to the out-of-plane easy axis. However, exchange bias does not extend to all molecules on the surface. On oxide antiferromagnets such as CoO we find no evidence of exchange bias for either TbPc or MnPc