Size and temperature effects on the Seebeck coefficient of thin bismuth films

The electrical resistivity and the Seebeck coefficient of thermally evaporated thin bismuth films of thicknesses from 300 to 1900 A have been measured in the temperature range 300470 K. The latter is negative and its magnitude is found to increase initially with increasing temperature, reach a maximum, and then decrease with a further rise in temperature. The temperature at which the Seebeck coefficient is maximum is found to be thickness dependent, decreasing with increasing thickness. The observed dependence is explained by considering that the Fermi energy is temperature dependent. Bismuth films show a negative temperature coefficient of resistivity. The thickness dependence of the electrical resistivity and the Seebeck coefficient of simultaneously prepared films are analyzed using the newer effective mean-free-path model. From the analysis, important material constants like the mean free path, the electron concentration, and the effective mass of electrons have been evaluated. © 1987 The American Physical Society.