The correlation of electrical conductivity with the microstructure of Ge₂Sb₂Te₅ thin films alloyed with Sn

In this research, the effects of Sn alloying on structure transformation and electrical characteristics of Ge₂Sb₂Te₅ (GST) thin films were studied. It was discovered that the SnTe phase formed in GST thin films when Sn content exceeded 26 at%, and the addition of Sn atoms expanded the lattice parameter, as a result of atomic radii difference between Ge and Sn atoms. Furthermore, temperature dependent sheet resistance measurements on the GST:Sn thin films were performed for the electrical characteristics to be studied. Sn substitution fraction of 16 at% was discovered to maximize the crystallization temperature of GST thin films. Compared to the GST thin films, crystallization temperature difference and lower amorphous resistance of the GST:Sn thin films were mainly due to lower bonding energy of Sn–Te. Moreover, the amorphous conductivity activation energies ( E _σ) corresponding to different grain sizes were calculated with the Arrhenius equation. The E _σ value of GST:Sn thin films decreased significantly as the Sn content increased due to grain size effects, which appears to improve the temperature stability of conductivity of phase change memory. (paper)