Hyunseok Kim

​

Having single-crystalline materialshas been crucial to realize high-quality devices. In this regard, epitaxy hasbeen a steppingstone approach to produce single-crystalline materials. However,it has been required to realize thin epitaxial films that are free fromsubstrates to be applied for emerging applications such as flexible electronics,wearable electronics, and edge computing. Recently, our team conceived remoteepitaxy that allows growing single-crystalline materials on graphene-coatedsubstrates. As the graphene has lattice transparency, single-crystalline film growthis available on graphene-coated substrates by following potential fluctuation comingfrom substrates. At the same time, the single crystalline films are peelable fromsubstrates because of the weak interface binding between the grown epilayer andgraphene-coated substrates, which makes the epilayers thin enough to be appliedto the emerging application. However, the approach has limitations in somesystems. For the remote epitaxy, Ni stickers are utilized for dry transfer topreserve the interface, which means that etching selectivity with Ni film hasto be preserved. However, some of the materials do not have etching selectivity.Therefore, it is impossible to use the Ni sticker for dry transfer. To avoidthis issue, polymer-based wet transfer was utilized, which does not allow remoteepitaxy because of poor interface quality. Instead, by making patterns on wet-transferredgraphene, epitaxy was enabled, mimicking selective-area epitaxy and lateralovergrowth. Although direct epitaxy happened at the patterned area, theepitaxial layers are still peelable as majority of the surface is stillgraphene. Thus, the proposed approach can be an alternative approach for thesystems where the remote epitaxy does not function.