Remote epitaxial growth of single-crystal cesium tin bromide perovskite on germanium substrates

We demonstrate the remote epitaxial growth of single-crystal cesium tin bromide (CsSnBr3) perovskite thin films on germanium substrates through a graphene-mediated van der Waals interface. The crystallographic orientation of CsSnBr3 is precisely controlled by the substrate orientation: single-domain growth with [100] orientation on Ge(100) and dual-domain growth with 45° rotation on Ge(110). Temperature-dependent nucleation studies reveal that increasing evaporation source temperature from 600 to 750 °C promotes larger domain formation due to enhanced adatom diffusion and reduced nucleation density. The transferred CsSnBr3 films exhibit excellent photoresponse with a stable photocurrent (0.03–0.05 μA) and fast response time, demonstrating the potential of remote epitaxy for high-performance lead-free perovskite optoelectronics.