STM OF THE (010) SURFACE OF ORTHORHOMBIC PHOSPHORUS

Scanning tunneling microscopy (STM) was used to image the freshly cleaved (010) surface of orthorhombic black phosphorus (BP) in air. The surface became oxidized and adsorbed moisture from the air. The hydrophilic and reactive nature resulted in a rough and changing surface, as revealed by the STM. During STM imaging the BP surface was continuously removed by the W probe in a layer-by-layer fashion. Nevertheless, high quality STM atomic resolution images were obtained after the tip inscribed a depression by locally etching away several layers on the substrate. The puckered nature of the surface structure and the associated [100] oriented channels were clearly observed. Higher resolution imaging revealed the zig-zag arrangement of phosphorus atoms separated by about 0.22 nm.