Next: 2.1 Steps Up: An Examination Hydrogen Desorption Previous: 1 Introduction Contents
Crystalline silicon forms a diamond FCC structure with a bond angle of
. Each silicon atom is bonded to four other silicon atoms; two
below and two above. This is the most stable state for the silicon
since all of the possible bonds are fulfilled. The silicon atoms on
the surface however have two available bonding sites. The silicon
atoms on the surface bond with the two atoms below but lack the two
atoms above to complete the traditional diamond structure. With each
bonding site filled the silicon atoms are closer to reaching their
lowest energy state. The surface atoms are not in the most
energetically favorable place because they have two bonds available.
To reduce the number of unfulfilled bonds, the silicon atoms on the
surface bond with each other along the (001) direction. This leaves
the surface atoms with one available bond. When the silicon atoms
bond with each other they are pulled towards each other and out of
their diamond lattice positions. Rows of silicon atom pairs form on
the surface. These are known as dimer rows. See Figure 1.
