CPM Seminar

A low temperature scanning force microscope (SFM) operating in a dynamic mode in an ultra high vacuum environment was used to study the Si(111) 7x7 reconstructed surface at 7.2K. Image quality comparable to that of high resolution scanning tunneling microscopy is demonstrated. Not only the twelve adatoms but also the six rest atoms of the unit cell are clearly resolved for the first time with SFM. In addition, the first measurements of the short range chemical bonding forces above specific atomic sites are presented. The magnitude of the observed frequency shift due to the chemical interaction is in good agreement with first principles computations. Comparison of the theoretical and measured interaction range demonstrates that the nearest atoms in the tip and sample relax significantly towards each other when the tip apex comes within a few angstrom of the surface.

Friday, December 17th 1999, 15:30
Ernest Rutherford Physics Building, Boardroom (room 104)