Our work began with the arrival of a new graduate student, unfortunately with no previous experience in surface physics. We therefore started on a simple, introductory study, the examination of a tungsten surface by field ion microscopy, to obtain experience with the technique. This was necessary as rhodium, our primary interest, requires quite careful operation. One of the first things noted was that in the tungsten sample under study, what appeared to be a dislocation core intersected the (110) surface, as seen in Fig. 1a. That this was truly a dislocation was tested by field evaporation. After one cycle of evaporation, the spiral returned to the original shape, as it should for a dislocation. A single tungsten atom was then deposited on this surface, and was allowed to diffuse at ~ 320 K. The mesh of adsorption sites observed in the center of the spiral was in agreement with the mesh on the flat plane. Much to our surprise, after a few observations the added atom disappeared, as indicated in Fig. 1b, a result duplicated in a repetition of this work. Under our conditions tungsten atoms do not evaporate, and do not move over large distances or over the edge, so these findings suggest rapid attachment of the atom in close vicinity to the core, a quite unexpected effect.            Unfortunately, we were not able to continue this work. While the system was being prepared for further examinations, we were informed that all our rooms and laboratories in the Engineering Science Building, where this study was being carried out, would have to be vacated promptly. Our operations and equipment were transferred to two laboratories in the Materials Research Laboratory. All instruments have now been largely reassembled and equipped with rhodium samples and sources. We expect to be back in normal operation rapidly, and will pursue our main theme, the free energy of rhodium atoms on Rh(110).

Fig.1. Dislocation loop on W(110) surface. a) FIM image of (110) surface. Bright dots show location of individual atoms. b) Trace of tungsten adatom diffusing near dislocation core and finally disappearing. Large dots indicate surface atoms, small ones give adatom location.

G. Antczak and G. Ehrlich, Jump processes in surface diffusion, Surf. Sci. Repts. 62, 39 – 61 (2007)