Study of the Superconducting Cs-doped WO3 Crystal Surface by Electron Backscattered Diffraction

The crystallographic surface structure of thermal vapor grown Cs X WO3 0.005≤x≤0.3 crystals was investigated locally by electron backscattered diffraction in the environmental scanning electron microscope. Monoclinic to hexagonal phase transformation was shown to take place upon Cs doping to nominal concentrations of x=0.005 and x=0.05, while monoclinic to trigonal phase transition was observed at a concentration of x=0.3. In particular, the 2D superconducting crystals, of x=0.005 nominal concentration, were of inhomogeneous crystallographic phase according to the local Cs doping. The superconducting Cs-doped regions of the hexagonal phase were shown to be epitaxially grown on the WO3 monoclinic crystal surface, the (0001) of this phase being parallel to the (001) plane of the WO3 crystal. Our results support previous observations in these 2D superconducting Cs X WO3 crystals.