Diamondoids
are nanoparticles made of only a handful of carbon atoms, arranged in
the same way as in diamond, forming nanometer sized diamond crystals.
Previously, researchers at the Advanced Light Source (ALS) at Lawrence
Berkeley National Laboratory demonstrated the fascinating capability of
these tiny little diamonds to act as a monochromator for electrons. In
short, a thin layer of diamondoids deposited on a metal surface will
first capture the electrons ejected from the surface below due to its
negative electron affinity. These electrons, which are emitted from the
metal with a wide variety of kinetic energies—or colors—are then
re-emitted by the diamondoid layer but with a very narrow energy
distribution. This property, which is unique to diamondoid, is believed
to enable the development of a new generation of electron emitters with
unprecedented properties.
In
photoemission electron microscopy (PEEM), electrons emitted from a
sample due to x-ray irradiation are used to obtain images of the
chemical or magnetic properties of a surface with high spatial
resolution. However, chromatic aberrations limit the resolution
typically to 20 nm due to the wide energy distribution of the emitted
electrons. While it is possible to add expensive and complex correction
elements to the microscope, this experiment demonstrates that the energy
spread can instead be reduced right at the source by using an
inexpensive, simple coating of diamondoids.
Using
this approach, the resolution of the PEEM3 microscope at ALS Beamline
11.0.1 improved significantly and researchers were able to attain
chemical information from 10 nm Au nanoparticles. The study exemplifies
how a problem not suited to conventional engineering solutions can be
solved with the help of the unique properties of a nanoparticle.