Substitutional Tin Acceptor States in Black Phosphorus

Nominally-pure black phosphorus (BP) is commonly found to be a p-type semiconductor, suggesting the ubiquitious presence of impurity species or intrinsic, charged defects. Moreover, scanning tunnelling microscopy (STM) images reveal long-ranged double-lobed defect features superimposed onto surface atomic lattice. We show that both doping BP and observed in STM can attributed substitutional tin impurities. samples produced through two common synthesis pathways contain impurities, we demonstrate ground state impurities negatively for wide range Fermi level positions within bandgap. The localised negative charge induces hydrogenic states bandgap it 2p sits at valence band edge gives rise images.