B. Venkataraman, G. Flynn, J. L. Wilbur
May 1, 1995
Citations
0
Influential Citations
49
Citations
Journal
The Journal of Physical Chemistry
Abstract
Scanning tunneling microscopy (STM) images of l-docosanol, 1-docosanethiol, didocosyl disulfide, and 1-chlorooctadecane on graphite are compared. The images of the I -docosanethiol and didocosyl disulfide show bright spots which are attributed to the positions of the S-H and S-S functional groups. The STM images of the l-docosanol and l-chlorooctadecane do not show such bright spots. Thb fact that both the S-H and S-S groups appear bright in the STM images indicates that the presence of an S atom on graphite results in a higher tunneling current when the tip scans over it compared to the tunneling current over a C, O. or Cl atom. The diff'erent behavior of the S atoms conrpiired to the O. C. and Cl atoms is discussed in terrns of the interactions between these atoms and the underlving graphite substrate. The persistent brightness of S atoms in the images of molecular adsorbates sugsests that sult'ur nrav serve as a useful "chromophore" for molecules imased bv STM.