Nanoscale Domain Structure and Defects in a 2-D WO3 Layer on Pd(100)

A stoichiometric two-dimensional (2-D) WO3 layer has been fabricated by vapor-phase deposition of (WO3)(3) clusters onto a Pd(100) surface and characterized by a combined experimental/theoretical multitechnique approach. The oxide forms a WO2 + O bilayer with a well-ordered c(2 X 2) structure, displaying at the full monolayer coverage a regular nanoscale pattern of antiphase domain boundaries, as revealed by low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM) and rationalized by DFT analysis as a consequence of elastic strain relief. The stability of the WO2 + O bilayer is provided by polarity compensation via charge rearrangement at the WO3/Pd interface and allows for surface redox chemistry via reversible release and restoration of oxygen atoms of the tungstyl or W=O groups.