THE STABILITY OF NANOSTRUCTURES FABRICATED ON SI(111)-7X7 SURFACE

The stability of nanometer- or atomic-scale structures will affect the quality of nanometer-scale devices significantly. In these experiment s, an ultrahigh vacuum scanning tunneling microscope was used to fabri cate nanometer or atomic structures and to observe the stability of th ese structures. Three typical movements of the atoms in fabricated str uctures were observed: (1) atom diffusion; (2) atoms transferring to t he hole site closing in on an intact unit cell; (3) atoms belonging to a defective unit cell diffused to another defective unit cell. In the se movements, the diffusion of atoms had a tendency to recuperate the integrity of the unit cell at all time. The naturally formed monoatomi c step and the fabricated bridge structure were studied. It was conclu ded that the structure maintaining the integrity of the 7 x 7 unit cel l was stable.