Characterization of cleaved surfaces of a monophosphate tungsten bronze

[001] surfaces of P4W8O32 obtained by cleavage in UHV are analyzed at room temperature by UPS, LEED and STM. Two types of facets are revealed. The type I shows periodic parameters very close to the parameters of the bulk unit cell. It corresponds to a relaxed (1x1) surface, and the surface defects may produce a (3x1) reconstruction. The type II facets show a periodicity of 7.45 E, that is the distance between two second neighboring tungsten sites and corresponds to facets parallel (001), the dense planes of the perovskite-like WO6 octahedra slabs. This parameter reflects also the width of the steps ending the WO6 octahedra slabs.