Chemical modification of silicon
surfaces
Greg Lopinski
Steacie Institute for Molecular Sciences
National Research Council Canada
There is increasing interest in the development of methods for
chemically modifying silicon surfaces for applications in conventional
microlectronics as well as in the development of novel hybrid organic/silicon
molecular devices and sensors. Atomically flat, hydrogen-terminated Si(111)
surfaces are used as the starting point for producing functionalized surfaces including surfaces terminated with
chlorine as well as with a range of organic functional groups (alkyl, phenyl, acid, ester, amino, thienyl,
hydrazide ...). The structure and chemical nature of these surfaces are
investigated with a number of techniques including scanning tunneling
microscopy and high-resolution electron energy loss spectroscopy (HREELS).
Electronic properties are examined with surface photovoltage and electrical
transport measurements along with HREELS, which can also provide information on
near surface carrier densities. We will discuss the use of chemical
modification to alter the conductivity of silicon through the control of band
bending as well as the exploitation of these effects for monitoring adsorption
and reaction events. In particular, chlorination leads to an enhanced surface
conductivity on low doped n-type Si(111) due to the formation of an inversion
layer. Hydrazide functionalized Si(111) surfaces exhibit large, reversible band bending increases upon exposure to
oxygen or iodine, demonstrating the chemical sensing potential of these
modified surfaces.