Remote Epitaxy-Assisted Mixed-Dimensional Integration of 3D Complex-Oxides and 2D Materials

A new method for growing and releasing three-dimensional (3D) complex-oxide layers in a single crystal form through an atomically thin graphene interlayer, known as remote epitaxy, has revolutionized the heterogeneous integration strategies, which were previously limited due to stringent lattice and processing restrictions. However, the transfer of graphene, which is a typical process for forming graphene on growth substrates, inevitably introduces a significant number of unwanted defects such as wrinkles, holes, process residues, and interfacial contamination. Such defects can disturb the remote interaction between the substrate and epitaxial layer through graphene, reducing the crystal quality and exfoliation yield of membranes. Recently, we developed a direct synthesis method for growing alternative two-dimensional (2D) materials, such as transition metal dichalcogenides (TMDs), on epitaxial substrates, which enables the creation of wafer-scale, defect-free 2D interlayers for reliable remote epitaxy of spinel CoFe₂O₄ (CFO) and garnet Y₃Fe₅O₁₂ (YIG) thin films of high-quality. The atomically clean van der Waals interfaces formed by direct growth of TMDs onto epitaxial substrates offer an ideal platform for high-throughput production of single-crystalline, freestanding complex-oxide membranes that can be released from substrates, but also for facile fabrication of a new class of mixed-dimensional heterogeneous systems that exhibit emergent physical phenomena at well-defined 3D/2D heterointerfaces. Based on this unique approach to integrating mixed-dimensional heterostructures in a scalable and controlled manner, we demonstrate new device concepts that take advantage of unusual physical coupling or decoupling at exotic 3D/2D interfaces, which are both fundamentally intriguing and practically useful.<br/><br/>Acknowledgement<br/>This work was supported by Korea Institute for Advancement of Technology (KIAT) grant funded by the Korea Government(MOTIE) (P0017305, Human Resource Development Program for Industrial Innovation(Global))