TERMINATION LAYER VARIATIONS ON THE CLEAVED RB1/3WO3(0001) SURFACE DETERMINED BY SCANNING-TUNNELING-MICROSCOPY

Cleaved (0001) surfaces of the hexagonal tungsten bronze, Rb1/3WO3, were studied by scanning tunneling microscopy (STM). Cleavage produces flat terraces with micron-scale dimensions that are separated by straight surface steps with heights equal to one half or one unit cell. High resolution images show that the well-ordered surface layers are occasionally interrupted by point defects. Two different contrast patterns with the periodicity of the bulk structure were observed and assigned to two different termination layers. The presence of different termination layers is an expected consequence of the cleavage process. Comparing the constant current STM images with ideal structures indicates that in this case image contrast is dominated by differences in the relative vertical positions of the surface atoms.