Photoinduced Disordering and Recovery in Colloidal Silicon Nanocrystals

Low toxicity silicon nanocrystals offer potential for use in applications that range from bio-labeling to solar energy conversion and LEDs. Small particles present reduced melting points and highly active surfaces that raise possibilities of loss of crystalline structure upon excitation as phonons are generated. We probe behavior of few-nanometer colloidal silicon particles and in particular focus on how the lattice responds to controlled fluence optical excitation. Using transient X-ray diffraction using optical excitation enabled by Beamline 11-ID-D at Argonne’s Advanced Photon Source, we correlate development of transient signals with number of photons absorbed to arrive at excitation densities that demonstrably disorder the initially crystalline lattices. Electronic consequences of this disordering are examined.