Thin films of (Bi0.25Sb0.75)(2)Te-3 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.. (C) 2002 Elsevier Science Ltd. All rights reserved.