An STM study of the UO 001/surface

The UO2 001.surface has been studied by elevated-temperature scanning tunnelling microscopy STM.and low-energy electron diffraction LEED.. The first reported STM images taken of the UO2 001.surface reveal a maze-like structure which can be resolved atomically at negative sample bias. The observed atomic periodicity corresponds to half a monolayer of oxygen arranged in slightly relaxed 1=1.out-of-phase domains along thew110xandw110xdirections. The shape and arrangement of the domains causes a splitting of the LEED beams which appears as crosses in the LEED pattern. STM also allows the observation of trenches with microscopic 1114facets which may contribute to a decrease in surface energy and stabilisation of the surface. q1999 Elsevier Science B.V. All rights reserved.