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The formal two-electron reduction of the cyclo-tri(phosphonio)methanide dication 12+ results in a ring-opening reaction via C–P bond cleavage to yield the unique phosphanyl-functionalized carbodiphosphorane 2. In situ spectroelectrochemical investigations of the reduction of dication 12+ and the oxidation of 2 give insights into the mechanism of this unusual and reversible bond cleavage reaction. Compound 2 features in total three lone pairs of electrons, facilitating the preparation of mono-, di-, and trigold complexes.

We demonstrate that the thermoelectric properties of epitaxial strontium titanate (STO) thin films can be improved by additional B-site doping of A-site doped ABO3 type perovskite STO. The additional B-site doping of A-site doped STO results in increased electrical conductivity, but at the expense of Seebeck coefficient. However, doping on both sites of the STO lattice significantly reduces the lattice thermal conductivity of STO by adding more densely and strategically distributed phononic scattering centers that attack wider phonon spectra. The additional B-site doping limits the trade-off relationship between the electrical conductivity and total thermal conductivity of A-site doped STO, leading to an improvement in the room-temperature thermoelectric figure of merit, ZT. The 5% Pr3+ and 20% Nb5+ double-doped STO film exhibits the best ZT of 0.016 at room temperature.

A novel superlattice structure based on epitaxial nanoscale layers of NbOx and Nb-doped SrTiO3 is fabricated using a layer-by-layer approach on lattice matched LAO substrates. The absolute Seebeck coefficient and electrical conductivity of the [(NbOx)a/(Nb-doped SrTiO3)b]20 superlattices (SLs) were found to increase with decreasing layer thickness ratio (a/b ratio), reaching, at high temperatures, a power factor that is comparable to epitaxial Nb-doped SrTiO3 (STNO) films (∼0.7 W m–1 K–1). High temperature studies reveal that the SLs behave as n-type semiconductors and undergo an irreversible change at a varying crossover temperature that depends on the a/b ratio. By use of high resolution X-ray photoelectron spectroscopy and X-ray diffraction, the irreversible changes are identified to be due to a phase transformation from cubic NbO to orthorhombic Nb2O5, which limits the highest temperature of stable operation of the superlattice to 950 K.

This work was supported by the King Abdullah University of Science and Technology (KAUST). Y.K.W. and S.D. were supported by National Natural Science Foundation of China (Grant No. 11674055). J.S.C. was supported by the Singapore National Research Foundation under CRP Award No. NRF-CRP10-2012-02 and IIP award No. NRF-IIP001-001.

Transparent thin-film thermocouples have been fabricated with indium tin oxide (ITO) and manganese doped indium tin oxide (Mn:ITO) as the positive and negative legs, respectively. Optical transparency of the thermocouples was above 85% in the visible region of the spectrum. Presence of Mn has been found to enhance the thermoelectric response, without significantly increasing the resistivity. Seebeck voltages of ~ 20 mV and ~ 31 mV have been obtained at 625 K, respectively, for the thermocouples with Mn:ITO legs having 1.6 at.% and 4.3 at.% Mn. The response has been found to be reproducible with an error of plusmn2%.

We report the evolution of high temperature thermoelectric properties of SrTiO3 thin films doped with Nb and oxygen vacancies. Structure-property relations in this important thermoelectric oxide are elucidated and the variation of transport properties with dopant concentrations is discussed. Oxygen vacancies are incorporated during growth or annealing in Ar/H2 above 800 K. An increase in lattice constant due to the inclusion of Nb and oxygen vacancies is found to result in an increase in carrier density and electrical conductivity with simultaneous decrease in carrier effective mass and Seebeck coefficient. The lattice thermal conductivity at 300 K is found to be 2.22 W m(-1) K(-1), and the estimated figure of merit is 0.29 at 1000 K.

Correlation of charge state of Mn with the increase in resistivity with Mn concentration is demonstrated in Mn-doped indium tin oxide films. Bonding analysis shows that Mn 2p3/2 core level can be deconvoluted into three components corresponding to Mn2+ and Mn4+ with binding energies 640.8 eV and 642.7 eV, respectively, and a Mn2+ satellite at ?5.4 eV away from the Mn2+ peak. The presence of the satellite peak unambiguously proves that Mn exists in the +2 charge state. The ratio of concentration of Mn2+ to Mn4+ of ?4:1 suggests that charge compensation occurs in the n-type films causing the resistivity increase. � 2010 American Institute of Physics.

Thermopower measurements in a range of 300-650 K along with room temperature optical absorption and electrical resistivity studies were performed on indium oxide (IO) and indium tin oxide (ITO) thin films grown by reactive dc sputtering. The thermopower of as-grown and oxygen-annealed IO and ITO films measured in Ar ambient displayed characteristics attributable to oxygen loss. The observations were substantiated with optical absorption and electrical resistivity results. � 2009 IOP Publishing Ltd.

Indium based transparent conducting oxides doped with magnetic elements have been studied intensively in recent years with a view to develop novel ferromagnetic semiconductors for spin-based electronics. In the present work, we have grown manganese doped indium tin oxide (Mn:ITO) thin films, onto Si and Si/SiO2 substrates by DC reactive sputtering of a composite target containing indium-tin alloy and manganese, in a gas mixture of oxygen and argon. Glancing angle X-ray diffraction (GXRD) studies reveal the polycrystalline nature of the films. Magnetic measurements carried out using vibrating sample magnetometer (VSM) suggest that the films are ferromagnetic at room temperature, with a saturation magnetization of ?22.8 emu/cm3. The atomic percentages of In, Sn, Mn and O, as estimated using Rutherford backscattering spectrometry (RBS) are 37.0, 4.0, 1.6 and 57.4, respectively. RBS measurements reveal that the interface of the films with Si substrate has a ?30 nm thick intermediate layer. This layer consists of oxygen, silicon, indium, tin and manganese, in the ratio 1:0.56:0.21:0.07:0.03, indicative of diffusion of elements across the interface. The films on Si/SiO2, on the other hand, have a sharp interface. � 2007 Elsevier B.V. All rights reserved.

In this study, the temperature dependent thermoelectric properties of sol–gel prepared ZnO and 3% Ga-doped ZnO (GZO) thin films have been explored. The power factor of GZO films, as compared to ZnO, is improved by nearly 17% at high temperature. A stabilization anneal, prior to thermoelectric measurements, in a strongly reducing Ar/H2 (95/5) atmosphere at 500 °C was found to effectively stabilize the chemically derived films, practically eliminating hysteresis during thermoelectric measurements. Subtle changes in the thermoelectric properties of stabilized films have been correlated to oxygen vacancies and excitonic levels that are known to exist in ZnO-based thin films. The role of Ga dopants and defects, formed upon annealing, in driving the observed complex temperature dependence of the thermoelectric properties is discussed.

We study epitaxial SrTiO3 interfaced with Nb-doped SrTi1-xNbxO3 (x = 0, 0.125, 0.25, 0.375, and 0.5) by full-potential density functional theory. From the electronic band structures obtained by our ab-initio calculations we determine the dependence of the induced metallicity on the Nb concentration. We obtain a monotonous increase of the carrier density with the Nb concentration. The results are confirmed by experiments for SrTi0.88Nb0.12O3 and SrTi0.8Nb0.2O3, demonstrating the predictive power and limitations of our theoretical approach. We also show that the Seebeck coefficient decreases monotonously with increasing temperature.

The influence of oxygen vacancies on the transport properties of epitaxial thermoelectric (Sr,La)TiO3 thin films is determined using electrical and spectroscopic ellipsometry (SE) measurements. Oxygen vacancy concentration was varied by ex-situ annealing in Ar and Ar/H2. All films exhibited degenerate semiconducting behavior, and electrical conductivity decreased (258–133 S cm−1) with increasing oxygen content. Similar decrease in the Seebeck coefficient is observed and attributed to a decrease in effective mass (7.8–3.2 me), as determined by SE. Excellent agreement between transport properties deduced from SE and direct electrical measurements suggests that SE is an effective tool for studying oxide thin film thermoelectrics.