Local Order and Crystallization of Laser Quenched and Ion Implanted Amorphous Ge1-xTex Thin Films

Amorphous films of Ge1-xTex (x = 0.37 and 0.64) prepared by sputtering, melt quenching, or ion irradiation were annealed up to 450 degrees C. The crystallized films consist of stoichiometric GeTe and precipitates of the excess element. The laser and ion irradiated Te-rich amorphous alloy exhibits higher stability with respect to the sputtered film, and an enhancement of the relative abundance of edge-sharing GeTe4 tetrahedra at the expense of Ge-rich tetrahedra occurs with respect to the as-deposited amorphous layers. The crystallization temperature increases with the density of Ge-Te bonds because this local rearrangement delays Te precipitation and the subsequent GeTe crystallization. Irradiation does not affect the stability of the Ge-rich alloy in which crystallization is limited by Ge mobility, and the induced local rearrangements are probably prevented by the low atomic diffusivity.