Se 85 Te 10 Bi 5 films of different thicknesses ranging from 126 to 512 nm have been prepared. Energydispersive X-ray (EDX) spectroscopy technique showed that films are nearly stoichiometric. X-ray diffraction (XRD) measurements have showed that the Se 85 Te 10 Bi 5 films were amorphous. Electrical conduction activation energy (DE s ) for the obtained films is found to be 0.662 eV independent of thickness in the investigated range. Investigation of the current voltage (I-V) characteristics in amorphous Se 85 Te 10 Bi 5 films reveals that it is typical for a memory switch. The switching voltage V th increases with the increase of the thickness and decreases exponentially with temperature in the range from 298 to 383 K. The switching voltage activation energy (e) calculated from the temperature dependence of V th is found to be 0.325 eV. The switching phenomenon in amorphous Se 85 Te 10 Bi 5 films is explained according to an electrothermal model for the switching process. The optical constants, the refractive index (n) and the absorption index (k) have been determined from transmittance (T) and reflectance (R) of Se 85 Te 10 Bi 5 films. Allowed non-direct transitions with an optical energy gap (E g opt ) of 1.33 eV have been obtained. DE s is almost half the obtained value of E g opt , which suggested band to band conduction as indicated by Davis and Mott.