Magnetocapacitance at the Ni/BiInO3 Schottky Interface

We report the observation of a magnetocapacitance effect at the interface between Ni and epitaxial nonpolar BiInO3 thin films at room temperature. A detailed surface study using X-ray photoelectron spectroscopy (XPS) reveals the formation of an intermetallic Ni-Bi alloy at the Ni/BiInO3 interface and a shift in the Bi 4f and In 3d core levels to higher binding energies with increasing Ni thickness. The latter infers band bending in BiInO3, corresponding to the formation of a p-type Schottky barrier. The current-voltage characteristics of the Ni/BiInO3/(Ba,Sr)RuO3/NdScO3(110) heterostructure show a significant dependence on the applied magnetic field and voltage cycling, which can be attributed to voltage-controlled band bending and spin-polarized charge accumulation in the vicinity of the Ni/BiInO3 interface. The magnetocapacitance effect can be realized at room temperature without involving multiferroic materials.

The effect of metal-insulator interface interactions on electrical transport in granular metals

We present an in-depth study of metal-insulator interfaces within granular metal (GM) films and correlate their interfacial interactions with structural and electrical transport properties. Nominally 100 nm thick GM films of Co and Mo dispersed within yttria-stabilized zirconia (YSZ), with volumetric metal fractions (φ) from 0.2-0.8, were grown by radio frequency co-sputtering from individual metal and YSZ targets. Scanning transmission electron microscopy and DC transport measurements find that the resulting metal islands are well-defined with 1.7-2.6 nm average diameters and percolation thresholds betweenφ= 0.4-0.5. The room temperature conductivities for theφ= 0.2 samples are several orders of magnitude larger than previously-reported for GMs. X-ray photoemission spectroscopy indicates both oxygen vacancy formation within the YSZ and band-bending at metal-insulator interfaces. The higher-than-predicted conductivity is largely attributed to these interface interactions. In agreement with recent theory, interactions that reduce the change in conductivity across the metal-insulator interface are seen to prevent sharp conductivity drops when the metal concentration decreases below the percolation threshold. These interface interactions help interpret the broad range of conductivities reported throughout the literature and can be used to tune the conductivities of future GMs.

Facile in situ redox synthesis of Au@Fe2O3 nanocomposites with multifunctional catalytic activity

Using freshly synthesized Fe(OH)2 matrix and HAuCl4 as precursor, l-lysine as stabilizer and linker, Au nanoparticles coated onto γ-Fe2O3 substrate were in-situ synthesized at room temperature. The Au@Fe2O3 hybrid composites with small highly dispersed gold particles (∼3 nm) exhibited high catalytic activity towards 4-nitrophenol reduction and the oxidation of benzyl alcohol. The results indicated the rate constant for 4-nitrophenol reduction was 5.3 × 10−2 s−1, and displayed efficient catalytic performance in terms of turnover number (TOF) of 134.8 h−1 for the oxidation of benzyl alcohol at 90 ± 1 °C. Furthermore, the facial electrode potential-driven in situ synthesis method paved the way of other metal nanoparticles over Fe2O3.

Composition-Dependent Charge Transport in Boron Carbides Alloyed with Aromatics: Plasma Enhanced Chemical Vapor Deposition Aniline/Orthocarborane Films

Boron carbide films, alloyed with aniline moieties, were deposited by plasma enhanced chemical vapor deposition (PECVD) from aniline and orthocarborane precursors and were found to exhibit composition-dependent drift carrier lifetimes as derived from I( V) and C( V)) measurements. For a film with an aniline/carborane ratio of 5:1, the effective drift carrier lifetimes are ∼80 μs at low bias voltage but quickly drop to a few microseconds with increasing bias. A film with a 10:1 aniline/carborane ratio, however, exhibited lifetimes of ∼6 μs, or less, at 1 kHz, and much smaller values at 10 kHz. These lifetimes are orders of magnitude longer than those in polyaniline films and comparable to those in PECVD carborane films without aromatic content. X-ray photoelectron spectroscopy (XPS), FTIR, and ellipsometry, combined with density functional theory (DFT)-based cluster calculations, indicate that aniline and orthocarborane moieties are largely intact within the films. Bonding occurs primarily between aniline C sites and carborane B sites, and the aniline coordination number per carborane icosahedron is ∼2 as the aniline/carborane ratio is increased from 3:1 to 10:1. This aniline/carborane coordination ratio independent of aniline/orthocarborane stoichiometry is consistent with the dependence of charge transport properties on aniline film content at high bias voltage.