Organic Nanostructures on Hydrogen-Terminated Silicon Report on Electric Field Modulation of Dangling Bond Charge State

We pursue dynamic charge and occupancy modulation of
silicon dangling
bond sites on H–Si(100)-2 × 1 with a biased scanning tunneling
microscope tip and demonstrate that the reactivity and mechanism of
product formation of cyclobutylmethylketone (CBMK) on the surface
at the active sites may be thus spatially regulated. Reactivity is
observed to be dependent on the polarity between tip and surface while
the area over which reactivity modulation is established scales according
to the dopant concentration in the sample. We account for these observations
with examination of the competition kinetics applicable to the CBMK/H–Si
reaction and determine how said kinetics are affected by the charge
state of DB sites associated with reaction initiation and propagation.
Our experiments demonstrate a new paradigm in lithographic control
of a self-assembly process on H–Si and reveal a variant to
the well-known radical mediated chain reaction chemistry applicable
to the H–Si surface where self-assembly is initiated with dative
bond formation between the molecule and a DB site.