Electrical, optical, and thermal properties of Sn-doped phase change material Ge₂Sb₂Te₅

In this article, effect of Sn on the electrical, optical, and thermal properties of Ge₂Sb₂Te₅ is studied. Ge₂Sb₂Te₅, Ge_1.55Sb₂Te₅Sn_0.45, and Ge_1.1Sb₂Te₅Sn_0.9 alloys are prepared by melt quenching technique and their thin films are prepared by thermal evaporation on glass substrates. These materials are then characterized by differential scanning calorimetry, X-ray diffraction, optical method, and impedance measurements. Doping with Sn maintains the NaCl-type crystalline structure of Ge₂Sb₂Te₅. Activation energy (E _a) for crystallization is calculated by Kissinger’s method. E _a decreases slightly from 2.56 eV for Ge₂Sb₂Te₅ to 2.24 eV for Ge_1.1Sb₂Te₅Sn_0.9. The distinct change in extinction coefficient (k) of Ge₂Sb₂Te₅ and Sn-doped amorphous films is found in the visible region. A large increase in optical contrast (C) is observed in the Sn-doped phase change materials. The phase change transition is studied using impedance measurements as a function of temperature. Impedance measurements show the appearance of nucleation centers in samples heated at temperatures below crystallization temperature (T _c) and above glass transition temperature (T _g).