Fig. 1: Silicon-compatible large-area preparation of WZ’ type α-In₂Se₃ thin films by an in-situ transport growth strategy.

a Schematic of the conventional remote transport growth (RTG) method with an inhomogeneous gaseous precursor distribution. b Side-view crystal models of β-, β’-, and α (ZB’)-In₂Se₃. The red balls represent Se atoms, and the blue balls represent In atoms. c Optical photographs of In₂Se₃ nanosheets by RTG. d Schematic of the in-situ transport growth (ITG) method. An amorphous In₂O₃ film was first deposited by PLD, followed by the selenization of In₂O₃ into In₂Se₃ with Se vapor in a CVD furnace. e Side-view crystal models of α (WZ’)-In₂Se₃. f Optical image of a WZ’ -In₂Se₃ thin film grown on SiO₂ /Si substrate with a size up to 1 cm by 1 cm. g The enlarged optical image of the area boxed in (f). Inset shows the atomic ratio (~2:3) of In and Se. h AFM topography of a randomly selected area on the film. The thickness of a single layer is determined to be ~0.8 nm from the line scan shown in the inset. i Typical θ−2θ XRD pattern of WZ’- In₂Se₃ film with diffraction peaks indexed as (00 L). j Raman spectra acquired at nine different positions. k Theoretical and typical experimental Raman spectra of WZ’ type and ZB’ type α-In₂Se₃ with a thickness of 18 nm.