A Scanning Tunneling Microscopy Observation of ($\sqrt{3}\times\sqrt{3}$) R30° Reconstructed Ni2P(0001)

A Ni2P(0001) single crystal surface has been studied in the framework of model catalysis with a low temperature scanning tunneling microscope (STM) under ultrahigh vacuum (UHV). We observed a previously unreported (√3×√3) R30° reconstruction and successfully recorded its atomically-resolved STM images. Two types of atomic arrangements have been found for this (√3×√3) R30° structure depending on annealing conditions during preparation. One shows a filled and the other one an empty network of polygons. Upon annealing to 940 K, only the latter empty type of structure has been observed.