LEED CRYSTALLOGRAPHIC DETERMINATION FOR THE RESTRUCTURED SURFACE FORMED BY PHOSPHORUS BONDED AT CU(110)

LEED crystallography is used to study the ordered ((2)(-11) (2)) surface structure formed on reacting PH3 with the Cu(110) surface followed by an anneal at 720 K. Intensity-versus-energy curves were measured with a video system for 13 diffracted beams at normal incidence, and they were analyzed with multiple-scattering calculations. The best correspondence between experimental and calculated I(E) curves indicates a new type of structural model in which a half-monolayer of P reconstructs the original metal surface, in effect by adding a quarter-monolayer of Cu atoms to form rows in the [112] direction. In this structure, each adsorbed P atom has six-fold coordination, and all Cu atoms in the top two metal layers bond to two P atoms. The average P-Cu length is 2.33 Angstrom, in reasonable correspondence with expectation from the structure of bulk Cu3P. Comparsions are made with other related systems.