Thermoelectric behaviour of (Bi0.5Sb0.5)2Te3 semiconducting alloy thin films
08 Oct 2001-Solid State Communications (Pergamon)-Vol. 120, Iss: 5, pp 217-220
Abstract: The Jain–Verma theory has been applied to the thermoelectric data of vacuum flash-evaporated and annealed polycrystalline thin films of (Bi0.5Sb0.5)2Te3 alloys of different thicknesses to study the nature of principal carrier scattering mechanism and also to know the extent of other scattering mechanisms, simultaneously. It is found that the value of the energy dependent scattering index parameter lies between −0.45 and −0.4. This indicates that, even though the principal scattering mechanism in the films is the normal lattice scattering, other scattering like ‘impurity’ scattering, surface scattering and grain boundary scattering may be present.
Topics: Phonon scattering (72%), Scattering (71%), X-ray Raman scattering (65%), Ionized impurity scattering (64%), Wide-angle X-ray scattering (61%)
04 Apr 2007-Journal of Applied Physics
Abstract: The thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3ω method at room temperature. The nanocrystalline thin films are grown on a glass substrate by a flash evaporation method, followed by hydrogen annealing at 250 °C. The structure of the thin films is studied by means of atomic force microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The thin films exhibit an average grain size of 60 nm and a cross-plane thermal conductivity of 0.8 W∕m K. The in-plane electrical conductivity and in-plane Seebeck coefficient are also investigated. Assuming that the in-plane thermal conductivity of the thin films is identical to that of the cross-plane direction, the in-plane figure of merit of the thin films is estimated to be ZT=0.7. As compared with a sintered bulk sample with average grain size of 30 μm and nearly the same composition as the thin films, the nanocrystalline thin films show approximately a 50% redu...
03 Oct 2002-Materials Research Bulletin
Abstract: Thin films of (Bi0.25Sb0.75)2Te3 with 2% excess Te of different thicknesses were prepared by the flash evaporation technique. Electrical resistivity and thermoelectric power were measured for different thickness films and at different temperatures. Applying Jain–Verma theory of carrier energy dependent relaxation time, thermoelectric data of thin films were analysed to understand the nature of scattering mechanisms in this thermoelectric material. The scattering parameter b was calculated from the thermoelectric and resistivity data. This gives us an indication about the nature of scattering processes in the before mentioned composition thin films. It is found from such an analysis of the thermoelectric data of thin films of the alloy with 2% excess Te that the scattering index parameter b varies in this material thin films from −0.2 to −0.1 and to positive values at higher temperatures.
22 Jan 2003-Thin Solid Films
Abstract: Resistivity and thermopower measurements were performed on thin films of Bi2(Te0.8Se0.2)3 prepared by flash evaporation technique. Applying the Jain–Verma theory to the experimental data of Bi2(Te0.8Se0.2)3, scattering index parameter was evaluated. The value of scattering index parameter was found to lie between −0.3 and −0.2. This indicates the presence of other scattering mechanisms, in addition to the lattice scattering.
17 Aug 2003-
Abstract: Bismuth and antimony are semimetals. The Bi/sub (1-x)/Sb/sub x/ alloys (0.04
01 Jan 2003-
Abstract: Bismuth and antimony are semimetals. The Bi,j.,,Sb, alloys (0.04
15 Jun 1978-Thin Solid Films
Abstract: A mathematical analysis based on the Mayadas-Shatzkes model indicates that we may define an “effective mean free path” in order to describe electronic conduction in both thin polycrystalline and monocrystalline metallic films. Under this condition a Fuchs-Sondheimer function can be introduced to evaluate the total film resistivity and its temperature coefficient in the presence of external surfaces. A possible extension to other theories derived from the Fuchs theory is mentioned.
01 Feb 1973-Thin Solid Films
Abstract: Using the Boltzmann transport equation, expressions for the electrical and thermal current densities in metallic films have been obtained previously. The expressions assumed that the relaxation time τ is constant in a second order approximation. In this paper, an analysis of transport properties has been carried out using a general energy dependence of the relaxation time, τ=aEb. It has been shown by the analysis that if b=− 1 2 there should be a size effect in the electrical conductivity, but the Seebeck coefficient is independent of size. From the given variation of δF/δB and QF/QB with the thickness of the film, the value of b, the energy dependence parameter, can be estimated. An estimation of b reveals information about the predominant scattering mechanism in metallic films. The experimentally observed size effect of the Seebeck coefficient in potassium has been compared with computed values.
01 Nov 1983-Journal of Applied Physics
Abstract: PbTe thin films of thicknesses ranging from 400 to 4000 A have been prepared by vacuum evaporation at a pressure of 5×10−5 Torr on clean glass substrates held at room temperature. The thermoelectromotive force of these films has been measured in the temperature range 300–600 K. It is found that thermoelectric power, SF varies anomalously with temperature, being constant at lower temperatures, and rapidly decreasing at higher temperatures. SF is found to be positive indicating that the samples are p type. The anomalous behavior is explained by assuming that at higher temperatures additional donor levels are generated due to creation and ionization of defects in the system.
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