Thin films of Bi2Te2Se1 of various thicknesses have been deposited on clean glass plates using the flash evaporation technique. Electrical resistance and thermoelectric power measurements have been carried out on these films in the temperature range 300-485 K. The thickness dependences of electrical resistivity and thermoelectric power of the films have been analyzed using the effective mean-free path model. The thickness dependence of activation energy of the films is explained by Seto's polycrystalline model. Various material parameters such as mean-free path and Fermi energy have been calculated from the analysis of experimental data. The thermoelectric power factor of the films has been calculated using the measured electrical resistivity and thermoelectric power values. © 1998 American Institute of Physics.

V. Damodara das

S. Selvaraj

Fulltext

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IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Size and temperature dependence of electrical resistance and thermoelectric power of bi2te2se1 thin films

Journal of Applied Physics

The thin films of Bi88Sb12 of different thicknesses have been vacuum deposited on glass and silicon substrates using the flash evaporation method. The structural characterization was carried out by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The composition and thicknesses of as-grown and annealed films were measured by the quartz crystal thickness monitor and Rutherford back scattering spectroscopy (RBS). The thermoelectric power and electrical resistivity measurement have been carried out on the films in the temperature range 100-300 K. The thickness dependences of electrical resistivity and thermoelectric power of thin films have been analyzed using the effective mean-free path model. The thermoelectric power factors of films have been calculated and the nature of carrier scattering in these films has been reported. © 2004 Elsevier Ltd. All rights reserved.

Vacuum

Size- and temperature-dependent thermoelectric and electrical properties of Bi88Sb12 alloy thin films

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. © 2002 Elsevier Science B.V. All rights reserved.

Thin Solid Films

Determination of the nature of principal scattering mechanism in well-annealed vacuum deposited thin films of the ternary thermoelectric material Bi2(Te0.8Se0.2)3

Thin films of different thicknesses have been vacuum deposited onto clean glass plates held at room temperature using the flash evaporation technique in a vacuum of 2 × 10-5 Torr. The structural characterization of the bulk and the thin films was carried out using x-ray diffraction, transmission electron microscopy, and selected area electron diffraction techniques. Electrical resistance and thermoelectric power of the films were measured in the same vacuum of 2 × 10-5 Torr in the temperature range 300-450 K. The conduction activation energy of the films was calculated using the electrical resistivity and thermoelectric power data of the films. The thickness dependence of the activation energy observed is attributed to the polycrystalline nature of the films. Grain growth and reorientation of the grains take place during the annealing process. The thickness dependence of electrical resistivity and thermoelectric power of the films are explained by the effective mean free path model [C. R. Tellier, Thin Solid Films 51, 311 (1978)]. The important physical parameters like mean free path, Fermi energy, power index of the energy dependant expression for the mean free path, the hypothetical bulk resistivity and the thermoelectric power have been calculated by the combined analysis of electrical resistivity and thermoelectric power. The electron-phonon scattering mechanism is found to be dominant in the material. © 1999 American Institute of Physics.

Thickness and temperature dependence of electrical properties of Bi2(Te0.1Se0.9)3 thin films

Thin films of Bi2(Te0.8Se0.2)3 semiconductor were prepared on clean glass plates in a vacuum of 2×10-5 torr. The bulk material (charge) was prepared by melting the appropriate quantities of the required elements in a quartz ampoule in a vacuum of 2×10-5 torr. Structural characterization of bulk and thin films was carried out using XRD analysis. Also, transmission electron microscopy and selected area electron diffraction techniques were employed for structural characterization of thin films. Variation of activation energy of the films with film thickness is attributed to the variation of grain size with film thickness. The thickness dependence of resistivity of the films is explained on the basis of the effective mean free path model. The mean free path of the electrons in this material was evaluated using this model. It is found that the mean free path decreases as the temperature increases due to the increased intensity of thermal vibrations of the lattice.

Solid State Communications

Electrical conduction studies on Bi2(Te0.8Se0.2)3 chalcogenide thin films

Thin films of different thicknesses have been vacuum (2 × 10-5 torr) deposited by the flash evaporation technique onto glass plates held at room temperature. In situ measurement of electrical resistance in vacuum (2 × 10-5 torr) as a function of time was carried out until the resistance stabilized. Then, on exposure to air by controlled admittance of air into the vacuum chamber, it was found that the resistance of the films increased as pressure increased. After air was admitted up to atmospheric pressure, the resistance was also found to increase as a function of time in the atmosphere. Also, it was observed that the resistance of the film during re-evacuation does not retrace the previous path during the exposure of the films and thus the resistance variation is not reversible. The variation of resistance taking place in the films in vacuum with time is attributed to the coalescence process. The agglomeration rates for the films of different thicknesses were obtained from the linear behavior of In(R/R0) vs time plot. The resistance variation of the films during the exposure to air is attributed to oxygen adsorption. It was found that the annealed films are less influenced by the exposure compared to the as-grown films. Adsorption of oxygen takes place on the external and internal surfaces of the films. The films were found to be ESR active. Structural analysis was carried out using the XRD and TEM techniques. © 1998 Elsevier Science Ltd. All rights reserved.

Time dependent electrical resistance of Bi2(Te0.4Se0.6)3 thin films in vacuum and on exposure to atmosphere

(Bi0.6Sb0.4)2Te3 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.

Semiconductor Science and Technology

Electrical conduction studies on (Bi0.6Sb0.4)2Te3 thin films

The effect of film thickness on the conduction activation energy and resistivity of flash evaporated Pb0.5Sn0.5Te thin films has been investigated. The conduction activation energy has been found to decrease with an increase in thickness. The observed variation of conduction activation energy with thickness has been explained using Seto's polycrystalline model. The linear reciprocal thickness dependence of electrical resistivity observed has been explained by the "effective mean free path model" of classical size effect. © 1995.

Journal	Data powered by TypesetJournal of Applied Physics
Publisher	Data powered by TypesetAmerican Institute of Physics Inc.
ISSN	00218979
Open Access	No