MATERIAL SCIENCE

Peak Growth

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Science  02 Dec 2005:
Vol. 310, Issue 5753, pp. 1391-1393
DOI: 10.1126/science.310.5753.1391d

There is wide interest in fabricating large, defect-free, three-dimensional periodic crystals for use in photonic applications. One simple method involves the growth of colloidal crystals; however, most such methods produce crystals with stacking faults and macroscopic cracks. The defects arise in part because the difference in free energy between the face-centered cubic and hexagonal close-packed structures is small.

Jin et al. found that by reducing the growth temperature from 65° to 24°C and by decreasing the concentration of particles in solution, they were able to grow crystals with both the (111) and the more desirable but less energetically favorable (100) orientations on a flat substrate. They explored the role of templating the substrate by building pillars of hydrogen silsesquioxane with spacings of 308 to 320 nm, on which they grew crystals with a particle diameter of 299 nm. By vastly slowing down the growth rate and tilting the substrate, they obtained crystals that were free of cracks and faults, although there was the odd defect where differently sized colloidal particles were located. The crack-free nature of the crystals is due to the underlying template, which forces the bottom layer of particles to take on a non-close-packed arrangement, giving the particles a bit of space to move about as the crystal grows and dries. — MSL

Nano Lett. 10.1021/nl051905j (2005).

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