Photoinduced growth of the crystalline phase of tellurium on a 1T′-MoTe2 matrix

Due to the growing demand for miniaturization and energy efficiency in modern electronic devices, there is a renewed interest for optoelectronic memories and sensors based on 2D materials. In particular, the molybdenum ditelluride (MoTe2) is one of the most promising materials for applications in nonvolatile phase-change memory devices, as its properties can be controlled by visible-light illumination. Among the several ways to synthesize MoTe2, the molybdenum oxide tellurization through isothermal close space sublimation (CSS) annealing in gas atmosphere is a simple and low-cost effective method for large-scale production of devices based on this layered material. Therefore, the understanding of the physical properties of MoTe2 thin films produced by this technique is crucial for future applications. Surprisingly, our results indicate that there is a photoinduced growth of the crystalline phase of tellurium on the 1T′-MoTe2 matrix even when the power density of the laser is low. From Raman spectroscopy investigations, we were able to show that nanometer-sized tellurium crystallites work as seed sites for the photocrystallization of tellurium. By assuming that the overall crystallization process is described by a kinetic approach that is based on the Kolmogorov–Johnson–Mehl–Avrami theory, our results indicate that the process is governed by an anisotropic organization of the tellurium atoms in helical structures during the crystal growth.