Transition metal compound surfaces II: The tungsten trioxide single crystal surface

The surface properties of macroscopic single crystals of tungsten trioxide have been investigated using low energy electron diffraction and Auger electron spectroscopy. The stoichiometric (100) surface shows evidence of distortion to triclinic symmetry, indicated by a doubled feature diffraction pattern. A WO₃ crystal surface grown several degrees away from the (100) plane exhibits a diffraction pattern which may be understood in terms of the formation of a [103] shear plane in the nonstoichiometric surface region. This surface is discussed in relation to the mechanism of oxidation of tungsten. Auger spectra provide support for a covalent bonding network in the WO₃ surface region, similar to that observed for sodium tungsten bronzes.