An STM study of the UO2(001) surface

The UO2(001) surface has been studied by elevated-temperature scanning tunn elling microscopy (STM) and low-energy electron diffraction (LEED). The fir st reported STM images taken of the UO2(001) surface reveal a maze-like str ucture which can be resolved atomically at negative sample bias. The observ ed atomic periodicity corresponds to half a monolayer of oxygen arranged in slightly relaxed (1 x 1) out-of-phase domains along the [110] and [(1) ove r bar 10] directions. The shape and arrangement of the domains causes a spl itting of the LEED beams which appears as crosses in the LEED pattern. STM also allows the observation of trenches with microscopic {111} facets which may contribute to a decrease in surface energy and stabilisation of the su rface. (C) 1999 Elsevier Science B.V. All rights reserved.