Professur Analytik an Festkörperoberflächen
Low temperature STM image:
Ordered and disordered phase of SnPc deposited 
on room temperature Ag(111) are coexisting .

Because of insufficient adsorbate mobility the ordered phase is not growing on cost of the disordered phase

A nucleus of a new ordered domain can be seen on the upper left part of the image. According to the substrate symmetry the orientation within this nuclues is rotated 
120° with respect to the large ordered domain.

Within the disordered phase short range ordering in 
terms of (more or less) linear molecular chains occurs.

 
Higher resolution of the disorderd phase:

The four-leaf clover shape of individual 
molecules is cleary visible.

Molecules with bright and dark centers can be distinguished. We assign that to different adsorption geometries (denoted as "up" and "down")

The image shows  molecular chains 
and agglomerates, which consist of 
up and down molecules, respectively
The ordered phase shows both adsorption geo-
metries as well. A unit-cell with a two-molecular 
base is suitable to describe the structure

Model of the proposed unit cell. 
The four molecules at the corners are up, 
the center molecule is down.

But also many defects - e.g. vacancies - occur.
Also in many cells the center molecule is down too.

M. Lackinger and M. Hietschold,
“Determining Adsorption Geometry of Individual Tin-Phthalocyanine Molecules on Ag(111)
- A STM Study at SubmonolayerCoverage”,
submitted to Surf.Sci. (2002)

M.Lackinger, 2002