Alkali-AssistedStitching Growth of Centimeter-ScalePtSe2 Films from Unidirectionally Aligned Millimeter-ScaleRibbons

Abstract Seamless stitching of aligned two-dimensional (2D) domains offers a promising route toward scalable single-crystal 2D materials but remains challenging for platinum diselenide (PtSe2), whose strong interlayer interaction favors vertical stacking over lateral growth. Here, we report a chemical vapor deposition strategy combining substrate engineering with OH-assisted growth to achieve stitched PtSe2 films. Localized prestrain followed by strain-relief annealing converts polycrystalline Au foils into centimeter-scale high-index single-crystal substrates, enabling the growth of dense, unidirectionally aligned millimeter-scale PtSe2 ribbons. Introducing NaOH into the precursor promotes lateral epitaxy while suppressing vertical overgrowth, allowing adjacent ribbons to stitch into continuous, predominantly single-crystal PtSe2 films down to the monolayer limit. The resulting films exhibit thickness-dependent electrical properties, evolving from semiconducting to bipolar semiconducting and semimetallic behavior. This strategy provides a practical route for scalable PtSe2 synthesis and highlights alkali-assisted epitaxy as a general approach for growing two-dimensional transition metal dichalcogenides.