Bulk Photovoltaic Effect in Single Ferroelectric Domain of SnS Crystal and Control of Local Polarization by Strain

The bulk photovoltaic effect (BPVE) in ferroelectrics, wherein spontaneous polarization can be reversed within crystals lacking centrosymmetry, encompasses the significant contribution of ferroelectric domain walls (DWs), known as DW‐PVE. Nevertheless, the separation between intrinsic BPVE within the domain and DW‐PVE remains unexplored in 2D ferroelectrics, notwithstanding its significant importance. In this study, sizable crystals of 2D ferroelectric SnS are successfully grown, facilitating a comprehensive yet intricate examination of domain configurations utilizing polarized optical microscopy and piezoresponse force microscopy. By properly selecting the large ferroelectric single domain within SnS crystals, uniform intrinsic BPVE across the domain is unequivocally demonstrated. Furthermore, to further enhance intrinsic BPVE, manipulation of strain poling increased photocurrent, suggesting that locally distributed polarizations due to imperfection introduced in SnS crystals are aligned by strain. These results will offer a new avenue for rigorous comprehension of DW‐PVE in 2D ferroelectrics.