PHYSICO-CHEMICAL PROPERTIES OF THE Ge(8)Sb(2-x)BixTe(11) BULKS AND THIN FILMS

In this work the structure, thermal, electrical and optical properties of Ge8Sb2-xBixTe(11) (x = 0; 1; 2) thin films were investigated. Thin films were prepared by Flash Thermal Evaporation (FE) and by Pulsed Laser Deposition (PLD) techniques. The amorphous structure of all as-deposited films were proofed by X-ray diffraction analysis. All samples crystallize in the structure of cubic rock salt with a space group Fm-3m after the heat treatment. The crystallization behavior of Ge(8)Sb(2-x)BixTe(11) thin films were studied by the thermal analysis. It was found that the substitution of Sb by Bi leads to the decrease of the crystallization temperature and activation energy of the studied samples. The electrical sheet resistance R-s of as-deposited thin films, measured by the four probe method according to van der Pauw showed that the difference in Rs values between the amorphous and crystalline states decreases by around 4 orders of magnitude. The refractive index was increasing with the increase of Bi concentration related with the higher polarizability of Bi in comparison with Sb. The optical contrast for studied materials were determined from reflectivity and it was found to be more than 20 %.