Tailoring Crystallization Kinetics of Chalcogenides for Photonic Applications

Chalcogenides possess interesting optical properties, which are attractive for a variety of applications such as data storage, neuromorphic computing, and photonic switches. Lately a group of covalently bonded chalcogenides including Sb2Se3 and Sb2S3 has moved into the focus of interest for such photonic applications, where high optical contrast as well as reliable and fast switching is of crucial importance. Here, these properties of Sb2Se3 are examined and compared with typical phase change materials such as GeSb2Te4 and Ge2Sb2Te5. Sb2Se3 is favorable for many photonic applications due to its larger band gap, yet, the maximum optical contrast achievable is smaller than for GeTe and Ge2Sb2Te5. Furthermore, crystallization needs significantly longer and exhibits a distinctively wider stochastic distribution of reflectances after crystallization, which provides challenges for the usage in photonic applications. At the same time, the glassy/amorphous state of Sb2Se3 is more stable. These differences can be attributed to differences in bonding of the crystalline state, which is more covalent for Sb2Se3. A quantum-chemical map can help to understand and explain these trends and facilitates the design of tailored materials for photonic applications.