Direct observation of the atomic structure of W {100} surfaces

Fully resolved atomic images of the W {100} plane are obtained with the field ion microscope at 21°K. The image structure is consistent with the (1 × 1) structure. If shifts of atoms in the 〈110〉 directions parallel to the plane have occurred as derived from LEED investigations in the temperature range of 100–370°K, then the shifts at 21°K are too small to be observed in the FIM.