Dimer structure of the Si(001)2 x 1 surface observed by low-temperature scanning tunneling microscope

Using a scanning tunneling microscope (STM) which can be operated in ultrahigh vacuum (UHV), low temperature (> 2.8 K), and magnetic field (< 11 T), we studied dimer structure on the Si(001)2 x 1 surface. Asymmetric (buckled) dimer structure was observed with positive sample voltages, while most of the dimers look symmetric with negative voltages. These observations suggest that the observed symmetric dimer in the filled state images is not intrinsic; neither static symmetric dimer nor flip-flopped asymmetric dimer, but a matter of STM imaging mechanism. Magnetic filed, up to 10 T, applied perpendicularly to the surface does not affect the STM imaging at 10 K. (C) 2003 Elsevier Science B.V. All rights reserved.