Site saturation and 3D diffusion-controlled growth in the crystallization of Sb70Te30 glasses

Abstract

Phase change materials take advantage of the significant contrast in electrical resistivity or optical reflectivity between their crystalline and amorphous phases, making them suitable for use as non-volatile memories, with chalcogenide materials standing out in this regard. One of the most suitable materials for non-volatile storage is the alloy of composition Sb70Te30 (atomic %). It is well known that when Sb70Te30 thin films are heated, they exhibit a sharp decrease in electrical resistance due to the transition between amorphous and crystalline states in a narrow temperature range. In this work, the crystallization kinetics of the Sb70Te30 amorphous thin films were studied using continuous heating calorimetric data and applying a procedure known as “master curve method”. As the isokinetic nature of the crystallization process was assessed for this alloy, the master transformation curve and its corresponding kinetic function could be obtained. The analysis performed allows us to conclude that the crystallization kinetics can be explained considering a three-dimensional growth controlled by diffusion of pre-existing nuclei (site saturation). The results are compared with previous works.