We are pleased to present a special topic issue on Novel Epitaxy of Functional Materials. Epitaxy of single-crystalline semiconductors lays the foundations for advanced electronics and optoelectronics by providing the active materials for devices. To achieve the highest device performance, single-crystalline films with minimal dislocation density are desired. Conventional approaches have limitations because of lattice mismatch and thermal expansion mismatch. Accordingly, several advanced approaches1–5 have been developed, such as low-temperature buffer approach, lattice-engineered buffer approach, metamorphic buffer approach, epitaxial lateral overgrowth, domain-matched epitaxy, van der Waals epitaxy, and remote epitaxy. Further, to achieve complex heterostructures with large lattice mismatch, researchers have developed alternative approaches such as lift-transfer and layer transfer,2,6 which give the freedom to transfer epitaxial materials onto target substrates.
This special topic covers several areas of recent progresses in the field of advanced epitaxy. One exciting area is the epitaxy of defects- and phase-controlled high-quality 2D materials such as monolayer WS2 and MoTe2 for electronics and optoelectronics. In one report by Xiang et al.7 the authors illustrate the origin of the incommensurate domain boundaries in 2D materials when they are grown on 3D substrates through van der Waals epitaxy. In another report by Tao et al.8 the authors present their perspective and understanding on roles of epitaxy on the fabrication of wafer scale semiconducting MoTe2 single crystals and the development of low-constant resistance devices. Another interesting and trending area is the epitaxy of 3D semiconductors or functional materials on 2D materials buffered substrates. Several groups present their efforts on understanding the roles of 2D buffer layer on van der Waals or remote epitaxy, or engineering the 2D/3D interface for designing epitaxy conditions. For example, Kim et al.9 point out that interfacial oxide layer formed at the 2D/3D substrate interface could weaken remote interaction thus hindering remote epitaxy. Borisenko et al.10 reveal the substantial effect of graphene domains on the epitaxial film. Chang et al.11 present the development of a transfer-free graphene-guided approach to develop high quality epitaxial AlN film, in which the authors attribute the high quality of the epitaxial film to the low wrinkle density of graphene. Additionally, Wang et al.12 present the enhanced van der Waals epitaxy of germanium through tuning the dipole moment of the substrate. Further, Oh et al.13 show the growth of ZnO nanostructures on hexagonal BN films, which are demonstrated for flexible sensors due to their mechanical flexibility.
We thank all the authors for sharing their works to this special topic. We also thank the editors and staff at the Journal of Applied Physics for their support. We also acknowledge the support from National Science Foundation Award No. 2024972.
