Debye Institute for Nanomaterials Science

110
Physical and Colloid Chemistry
Investigation and Manipulation of Dislocations and Stacking Faults in Colloidal
Crystals
Jan Hilhorst, J.hilhorst@uu.nl, phone: 030 - 253 36 50
Sponsor: UU, since November 2007
Supervisors: Dr. Andrei V. Petukhov, Prof. dr. Henk N. W. Lekkerkerker
Scanning transmission X-ray microscopy (STXM), confocal fluorescence microscopy, focused ion beam
lithography
Colloids are particles with a size roughly between 1 nm and 1 μm in size. Such particles are small
enough to exhibit Brownian motion, like molecules and atoms, but move much slower and are
directly observable using visible light. This makes them ideal for studying processes related to
crystallization, such as nucleation and growth dynamics, as well as annealing and final crystal structure.
Their size also makes them attractive building blocks for photonic materials. If the periodicity of a
colloidal crystal is right and a large refractive index contrast exists between the particles and their
surroundings, a photonic band gap opens up; a band of photon energies that cannot propagate in the
crystal. Photonic crystals are under investigation for application in solar cells, low threshold lasing,
optical communication and even optical computing, but all of these require highly perfect crystals.
Colloidal self-assembly, however, results in crystals that are far from perfect. The occurrence of point,
linear and planar defects is frequent and hard to control. By studying the properties of these defects
and the mechanisms by which they grow, we hope to find ways to prevent their inclusion or to be
able to control their positioning. Using confocal fluorescence microscopy and X-ray microscopy, we
study defect linear and planar defects in detail, relating their presence to the overall crystal structure.
Using the knowledge obtained in this way, we can prepare crystal growth templates to selectively
introduce faults to influence the final crystal structure, as shown in figure 1 for a real crystal.
Figure 1: Side view of a face-centered cubic colloidal crystal into which stacking faults have been grown at predetermined
positions.