Local Order and Crystallization of Laser Quenched and Ion Implanted Amorphous Ge[sub 1−x]Te[sub x] Thin Films

Abstract

Amorphous films of Ge 1-x Te x (x = 0.37 and 0.64) prepared by sputtering, melt quenching, or ion irradiation were annealed up to 450°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 GeTe 4 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.