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Journal ArticleDOI

Electrical conduction studies on thin films

01 Feb 1997-Semiconductor Science and Technology (IOP Publishing)-Vol. 12, Iss: 2, pp 195-202
TL;DR: In this paper, the activation energy for conduction (in annealed films) is found to be thickness dependent and this can be explained with the help of the grain-boundary trapping model.
Abstract: thin films of different thicknesses were deposited by the flash evaporation method onto cleaned glass plates held at room temperature. Structural characterization was carried out using x-ray diffraction and transmission electron microscopy which revealed that the films are polycrystalline and the grain size increases with increasing thickness. Electrical resistivity was measured in the temperature range 300 - 450 K during two cycles of heating and cooling. During the first heating, irreversible behaviour of conductivity has been observed. Semiconductor-like behaviour has been observed in the annealed films and also during the first cooling and subsequent heating - cooling cycles. The activation energy for conduction (in annealed films) is found to be thickness dependent and this can be explained with the help of the grain-boundary trapping model. The thickness dependence of electrical resistivity (in annealed films) has been analysed using the effective mean free path model. From the analysis, important material constants like the mean free path and the electron concentration have been evaluated.
Citations
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Journal ArticleDOI
TL;DR: In this article, Bismuth-telluride-based alloy thin-film thermoelectric generators are fabricated by a flash evaporation method and the output voltage and the maximum output power near room temperature are estimated as a function of the temperature difference between hot and cold junctions of the thin-filtered generators.
Abstract: Bismuth–telluride-based alloy thin film thermoelectric generators are fabricated by a flash evaporation method. We prepare Bi 0.4 Te 3.0 Sb 1.6 (p-type) and Bi 2.0 Te 2.7 Se 0.3 (n-type) powders for the fabrication of the flash evaporated thin films. The overall size of the thin film thermoelectric generators, which consist of seven pairs of legs connected by aluminum electrodes, is 20 mm by 15 mm. Each leg is 15 mm long, 1 mm wide and 1 μm thick. We measure the output voltage and estimate the maximum output power near room temperature as a function of the temperature difference between hot and cold junctions of the thin film thermoelectric generators. In order to improve the performance of the generators, a hydrogen annealing process is carried out at several temperatures from 25 °C to 250 °C. The highest output voltage of 83.3 mV and estimated output power of 0.21 μW are obtained from a hydrogen annealing temperature of T a = 250 °C and a temperature difference of Δ T = 30 K. The hydrogen annealing temperature of T a = 250 °C also results in the best electrical performance for both p-type thin film (Seebeck coefficient = 254.4 μV/K, resistivity = 4.1 mΩ cm, power factor = 15.9 μW/cm K 2 ) and n-type thin film (−179.3 μV/K, 1.5 mΩ cm, 21.5 μW/cm K 2 ).

170 citations

Journal ArticleDOI
TL;DR: In this article, X-ray diffraction and energy dispersive spectrometry combined with electrical measurements such as Seebeck coefficient and electrical resistivity were used for the thermoelectric thin films characterization.

97 citations

Journal ArticleDOI
TL;DR: In this paper, the authors obtained a value of Z equal to 0.21×10 −4 K −1 for α =40 μV-K −1 and ρ =50 μΩ·m for P-type material and Z of about 0.17×10−3 K − 1 for α=90 μV−K − 1 and π =30 μξm for N −type material (at 300 K).
Abstract: (Bi 2 Te 3 ) 0.9 (Bi 2 Se 3 ) 0.1 for N-type material powder and (Bi 2 Te 3 ) 0.25 (Sb 2 Te 3 ) 0.75 for P-type material powder were evaporated by a flash evaporation technique. We obtained a value of Z equal to 0.21×10 −4 K −1 for α =40 μV K −1 and ρ =50 μΩ·m for P-type material and Z of about 0.17×10 −3 K −1 for α =90 μV K −1 and ρ =30 μΩ·m for N-type material (at 300 K), for 1 μm layer thickness deposited over polyimide substrate, before annealing. We show that after annealing at 250°C under He atmosphere, the figure of merit of the layers increases to Z =3.2×10 −3 K −1 for α =240 μV K −1 and ρ =12 μΩ·m for P-type material and Z =1.6×10 −3 K −1 for α =200 μV K −1 and ρ =15 μ Ω·m for N-type material (at 300 K). With these fabrication parameters, we realised three different structures of micromodule Peltier (MMP) junction and we obtained a maximum value for temperature drop between hot and cold sides of ≈3.4 K. This result is very promising in order to develop MMP.

74 citations

Journal ArticleDOI
TL;DR: In this article, annealed N-type bismuth telluride thin films of different thicknesses were deposited on cleaned glass substrate at room temperature by co-sputtering technique.

47 citations

Journal ArticleDOI
TL;DR: In this paper, annealing in argon ambient at atmospheric pressure is carried out for 1h in the temperature range from 200 to 400°C in order to enhance the transport properties of the thin films.

40 citations

References
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Book
01 Jan 2001

19,319 citations

Book
01 Jan 1956
TL;DR: In this article, the authors present a chemical analysis of X-ray diffraction by Xray Spectrometry and phase-diagram Determination of single crystal structures and phase diagrams.
Abstract: 1. Properties of X-rays. 2. Geometry of Crystals. 3. Diffraction I: Directions of Diffracted Beams. 4. Diffraction II: Intensities of Diffracted Beams. 5. Diffraction III: Non-Ideal Samples. 6. Laure Photographs. 7. Powder Photographs. 8. Diffractometer and Spectrometer. 9. Orientation and Quality of Single Crystals. 10. Structure of Polycrystalline Aggregates. 11. Determination of Crystal Structure. 12. Precise Parameter Measurements. 13. Phase-Diagram Determination. 14. Order-Disorder Transformation. 15. Chemical Analysis of X-ray Diffraction. 16. Chemical Analysis by X-ray Spectrometry. 17. Measurements of Residual Stress. 18. Polymers. 19. Small Angle Scatters. 20. Transmission Electron Microscope.

17,428 citations

Journal ArticleDOI
TL;DR: In this article, Boron doses of 1×1012-5×1015/cm2 were implanted at 60 keV into 1-μm-thick polysilicon films and Hall and resistivity measurements were made over a temperature range −50-250 °C.
Abstract: Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...

2,657 citations

Journal ArticleDOI
E.H. Sondheimer1
TL;DR: The mean free path of electrons in metals has been studied in this paper, where the authors show that electrons follow a straight line along the path of the electron in the metal atom.
Abstract: (2001). The mean free path of electrons in metals. Advances in Physics: Vol. 50, No. 6, pp. 499-537.

2,273 citations

Journal ArticleDOI
A. F. Mayadas1, M. Shatzkes1
TL;DR: In this paper, the total resistivity of a thin metal film is calculated from a model in which three types of electron scattering mechanisms are simultaneously operative: an isotropic background scattering (due to the combined effects of phonons and point defects), scattering due to a distribution of planar potentials (grain boundaries), and scattering by the external surfaces.
Abstract: In this paper, the total resistivity of a thin metal film is calculated from a model in which three types of electron scattering mechanisms are simultaneously operative: an isotropic background scattering (due to the combined effects of phonons and point defects), scattering due to a distribution of planar potentials (grain boundaries), and scattering due to the external surfaces. The intrinsic or bulk resistivity is obtained by solving a Boltzmann equation in which both grain-boundary and background scattering are accounted for. The total resistivity is obtained by imposing boundary conditions due to the external surfaces (as in the Fuchs theory) on this Boltzmann equation. Interpretation of published data on grain-boundary scattering in bulk materials in terms of the calculated intrinsic resistivity, and of thin-film data in terms of the calculated total resistivity suggests that (i) the grain-boundary reflection coefficient in Al is \ensuremath{\approx} 0.15, while it is somewhat higher in Cu; (ii) the observed thickness dependence of the resistivity in thin films is due to grain-boundary scattering as well as to the Fuchs size effect; and (iii) the common observation that single-crystal films possess lower resistivities than polycrystalline films may be accounted for by grain-boundary effects rather than by differences in the nature of surface scattering.

1,842 citations