On the crystallization of thin films composed of Sb3.6Te with Ge for rewritable data storage

This article addresses the crystallization of amorphous Sb3.6Te films (40 nm thick) and 5 at. % Ge containing Sb3.6Te films (10, 20, and 40 nm thick) as studied with transmission electron microcopy using in situ annealing. These materials exhibit growth-dominated crystallization, in contrast to the usual Ge2Sb2Te5 that shows nucleation-dominated crystallization. Particularly the crystal-growth velocity in these systems has been measured as a function of temperature from which the activation energy for growth can be derived. The strong effect of the 5 at. % Ge addition on the total crystallization behavior is revealed by the following four phenomena: Ge increases the crystallization temperature (from 95 to 150 degreesC), increases the activation energy for growth (from 1.58 to 2.37 eV), increases the nucleation rate and decreases the growth anisotropy. The crystallites have a special transrotational structure and a mechanism responsible for the development of this special structure is delineated.