Single-crystal is a research area in materials science and solid-state physics that focuses on studying the properties and behavior of materials with a very high degree of structural order at the atomic level. Single crystals are defined as materials in which the atoms are arranged in a repeating, three-dimensional pattern without any interruptions or defects. This high level of structural perfection allows researchers to investigate the intrinsic properties of the material, such as its electronic, optical, and mechanical properties, in a more controlled and precise manner. Single-crystal research is important for understanding the fundamental principles of materials science and for developing advanced technologies in fields such as semiconductors, photonics, and superconductors.