Tunability of the Optical Properties of Transition-Metal-Based Structural Phase Change Materials

Phase transitions are an intriguing yet poorly understood aspect of transition-metal-based materials; these phase transitions can result in changes to the refractive index, absorption coefficient, and other optical properties of the materials. Transition-metal-based materials exist in a variety of crystalline phases and also have metallic, semi-metallic, and semi-conducting characteristics. In this review, we demonstrate that alloyed W- and Mo-based dichalcogenides enable phase transitions in structures, with phase transition temperatures that are tunable across a wide range using various alloy models and modern DFT-based calculations. We also analyze the tuning the optical bandgap of the metal oxide nanoparticles through doping of the transition metal in a manner that is suitable for optical switching and thermal imaging. After the introduction and a brief illustration of the structures and their exceptional properties, we discuss synthetic methodologies and their application as part of important strategies toward the enhanced performance of transition-metal-based dichalcogenides and oxides. In the end, our conclusion highlights the prospects of 2D materials as phase transition materials due to their advantages in terms of scalability and adaptability.