OBSERVATION OF 7X7 RECONSTRUCTED STRUCTURE ON THE SILICON (111) SURFACE USING ULTRAHIGH-VACUUM NONCONTACT ATOMIC-FORCE MICROSCOPY

Unlike ultrahigh vacuum (UHV) scanning tunneling microscopy (STM), the effectiveness of UHV in UHV atomic force microscopy (AFM) has not been verified. Intensive interaction between tip and sample in UHV often damages the sample surface in the contact mode. Although noncontact (NC) AFM is effective in protecting the sample surface, it has failed to provide atomic-level resolution. We used a stiff silicon cantilever (similar to 40 N/m) capable of STM imaging, and succeeded in obtaining the first atomic-resolution images of Si(111)7 x 7 reconstruction in NC AFM at a tip-sample distance almost equal to that for STM imaging.