Nanoindentation is a common method for studying defect formation in
crystalline films. A very small point indents the material, ensuring
only a single crystalline region is probed. We study "nano" indentation
in thin colloidal crystal films. Each colloidal particle plays the role
of an atom; however, the particles can be imaged with a microscope and
their individual dynamics can be measured. The nanoindenter is a sewing
needle, which has the right scale relative to the colloidal particles.
The behavior is visualized using laser-diffraction microscopy, where
diffracted laser light is imaged (left). The video shows nucleation
of defects.
Individual particles are imaged with confocal
microscopy (right). The video shows the thermally-induced nucleation
and growth of dislocations.
Only particles whose order is distorted are displayed. The behavior of
the colloidal crystal is remarkably similar to that of atomic films,
but allows thermally induced dislocations to be directly visualized.
Harvard MRSEC (DMR-0820484)
