A figure of merit for transparent electrode materials has been defined by φTC=T10/Rs, where T is the optical transmission and Rs is the electrical sheet resistance. Expressions are derived to predict the transparent electrode properties of a material from its fundamental electrical and optical constants. The performance of thin metal films is compared to semiconducting oxide coatings.
Thin films of semiconducting n-type cadmium stannate (Cd2SnO4) have been coated onto different substrate materials by rf sputtering. The films are transparent in the visible and near-infrared part of the optical spectrum and electrically conductive. Conductivities as high as 6500 Ω−1 cm−1 have been achieved. Transparent electrode coatings can be prepared which have 1 Ω/square electrical sheet resistance and 85% average optical transmission between 5000 and 6500 Å.
Activated carbon adsorbs arsine in an inert atmosphere by physical adsorption and chemisorption. The physically adsorbed arsine desorbs readily at room temperature, which must be taken into consideration when activated carbon is used to remove arsine from effluent gas. Chemisorption is facilitated by copper and chromium present on the carbon surface as oxides. During chemisorption the arsine reduces both oxides. Upon exposure to air an exothermal oxidation reaction occurs reverting the copper and arsenic to their oxides but leaving the chromium sites in their reduced Cr3+ state.
The room-temperature lattice thermal conductivity of Zn3As2 is 0.012 W/cm·°C; that of Cd3As2 is 0.014 W/cm·°C or less. Anomalously low thermal conductivities (as much as 30% below calculated values) are found for samples of Cd3As2 and Cd-rich alloys of Cd3As2 with Zn3As2 where the electrical conductivity is high (>103 Ω−1 cm−1). Thermal conductivities for Cd3As2 samples fall into two groups: Samples doped with an element which is expected to enter the anion sublattice have normal thermal conductivities, while undoped samples or those doped with an element which should enter the cation sublattice tend to have anomalously low thermal conductivities. High electron mobilities and general lack of correlation of carrier concentration with thermal conductivity indicate that the anomaly is not in the electronic component of thermal conductivity. Instead, doping experiments, as well as the temperature dependencies of thermal conductivities indicate that the anomaly is entirely in the lattice component and is due to a lattice defect in the anion sublattice, probably an As vacancy. Although the lattice thermal conductivity of some samples of Cd3As2 appears to be only 0.003–0.004 W/cm·°C, their electron mobility is 104 cm2/V·sec. To explain the apparently enormous phonon scattering cross-section of the lattice defect, it is suggested that the phonon scattering may involve the transitions of localized electrons from one type of As site (vacancy) to another (there are three different types of As sites in Cd3As2).
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