Are there limits to rational chemical synthesis?

Seeded 2D epitaxy of large-area single-crystal films of the van der Waals semiconductor 2H MoTe 2

“…For example, transforming a polycrystalline 2D thin film into a single crystal only by thermal annealing must overcome the high energy barrier of rotating a 2D crystal domain on a substrate (17). Recently, graphene, a single-crystalline 2D semimetal, and hexagonal boron nitride (hBN), an insulator, were grown on single-crystalline metallic substrates or a molten metal surface by ensuring an identical crystal orientation of all the grains to avoid any grain boundaries during coalescence (18)(19)(20)(21)(22). However, for 2D semiconductors grown on a single-crystalline substrate, although the film has essentially one crystallographic orientation, translational grain boundaries still exist because of the presence of imperfectly stitched domains (23,24).…”