Effect of bismuth ion implantation on the crystallization temperature of the amorphous Ge2Sb2Te5 thin films

Bismuth doped Ge2Sb2Te5 thin films were prepared by magnetron sputtering of Ge2Sb2Te5 target with following ion implantation of Bi. Thin film compositions and elemental distribution across the film thicknesses were determined. An amorphous state of the as-deposited undoped and Bi-doped Ge2Sb2Te5 thin films was confirmed by X-ray diffraction. Temperature dependencies of the resistivity for Bi-doped Ge2Sb2Te5 thin films were measured. Two resistivity drops due to the crystallization and transformation from the cubic to hexagonal structure were determined. Decreases of the onset temperatures for the first and second transitions from 169.3 to 120.3 °C and from 188.0 to 153.0 °C with the increase of Bi concentration were found. It was shown, that the resistivity of the amorphous films sufficiently decreases with Bi concentration, while the variation of resistivity for the crystallized state is much smaller.