R&D: Explosive Crystallization Characteristic of Ge–Cu–Te Thin Films for Phase-Change Memory

Crystal Growth & Design has published an article written by Ming Wang, and Leng Chen, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.

Abstract: “Ge–Cu–Te thin films were investigated experimentally for their initial crystallization characteristics and their correlation with electrical behaviors as phase-change materials for application in phase-change random access memory (PCRAM). Explosive crystallization (EC) with random orientation was observed as an initiating effect on crystallization during the early stage of crystallization for Ge–Cu–Te thin films. Both the tetrahedral coordination environment and triangular Cu atoms clusters consisting of threefold rings for Ge–Cu–Te thin films contribute to the initiation of EC. Crystallization progresses from the surface toward the bulk of the thin films, resulting in grain growth through the thickness of the thin films. Thicker films can encourage EC by reducing heat loss and producing a thicker liquid layer as a result of more significant temperature gradients near the phase-change front. Moreover, providing additional external heat by extending the annealing time also pushes EC. Finally, electrical transport measurements using the Hall system demonstrated that conductivity is increased by a more continuous EC network that concentrates more carriers. The authors consider that the above results are beneficial for understanding the phase-change mechanism of Ge–Cu–Te phase-change materials.“