The
principles of photography - light strikes metallic salts in an emulsion
and frees atoms to nucleates clusters in the latent image; the clusters
increase in size in the developer to form visible pixels and produce
the final image - have been catapulted into the 21st
century.
CNRS
teams at the "Centre de spectrométrie nucléaire
et de spectrometrie de masse" (Center for Nuclear Spectrometry
and Mass Spectrometry), the "Laboratoire de minéralogie
et de cristallographie de Paris" (Paris Mineralogy and Crystallography
Laboratory), the "Unité mixte CNRS-Saint-Gobain "Surface
du verre et interfaces" (SVI, jointly-run research unit on Glass
Surface and Interfaces), collaborating with the Corning Research Center
in Fontainebleau, France, have simulated the photographic process
using an ion beam. They have demonstrated that at room temperature,
irradiating glass containing metal oxides with ions with an energy
of a few megaelectron volts (MeV) initiates nucleation of pure metal
nanocrystals with perfect density control. Perfect size control is
then provided through heat treatment. The effects of nano- and microcrystals
on the optical properties of glass have been known for centuries -
the stunning colors of stained glass in cathedrals are mainly due
to the presence of such crystals - but their mechanism of formation
has until now been obscured by the complex chemistry of glass.
The
ion beam technique -particularly when combined with lithography- may
have applications in optoelectronics. For example, the presence of
nanocrystals in silica may make its refractive index dependent on
the intensity of the irradiation (and not solely on the wavelength).
Such non linear properties will enable optical switches to be produced
for optic fibers.
