UW MRSEC - Fast Crystal Growth at the Surface of an Organic Glass

Y. Sun, K. L. Kearns, L. Yu, M. D. Ediger (DMR #0520527)

Films thicker than 400 nm show this dense crystal morphology, but films thinner than 180 nm show a fibrous morphology.

Amorphous indomethacin (an anti-inflammatory drug) crystallizes more than 100 times faster at the surface than in the bulk. A crystal layer spreads quickly across the surface without penetrating the interior.

Because of the importance of this process for preparing amorphous pharmaceuticals and for understanding fundamental aspects of crystal growth, we have investigated the thickness of the surface crystals. We conclude that the crystal layer is 200 – 400 nm thick. This is about 100 times thicker than the region of high mobility at the surface that is believed to be responsible for fast surface crystal growth.