SCANNING PROBE MICROSCOPY OF CLEAVED MOLYBDATES - ALPHA-MOO3(010), MO18O52(100), MO8O23(010), AND ETA-MO4O11(100)

Scanning probe microscopy was used to examine the cleaved surfaces of four binary molybdates: alpha-MoO3(010), Mo18O52(100), Mo8O23(010), an d eta-Mo4O11(100). The Mo18O52(100) and Mo8O23(010) surfaces were imag ed in air and vacuum using scanning tunneling microscopy (STM). The co ntrast associated with two types of surface/crystallographic shear (CS ) plane intersections has been unambiguously identified; shear normal to the surface creates a line of vertical relief 1.5 Angstrom high and shear in the surface plane creates a line of dark contrast. The contr ast from the surface/CS plane intersection arises, in part, from local variations in the electronic properties. These signatures are easily distinguished from features on the fully oxidized alpha-MoO3(010) surf ace. STM images of eta-Mo4O11(100) reveal a surface terminated by tetr ahedral groups. In each case, we find that the atomic-scale contrast c an be interpreted based on the arrangement of surface polyhedra that i s expected to result from cleavage of the longest, weakest bonds. (C) 1996 Academic Press,Inc.