Published in Physical Review Letters, Volume 106, Issue 23, June 10, 2011, pages 1-4.
Copyright © 2011 American Physical Society. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Physical Society. The following article appeared in Physical Review Letters and may be found at http://dx.doi.org/10.1103/PhysRevLett.106.235501.
NOTE: At the time of publication, the author Gregory Scott was not yet affiliated with Cal Poly.
Amorphous silicon is an important material, amidst a debate whether or not it is a glass. We produce amorphous Si surfaces by ion bombardment and vapor growth, and image discrete Si clusters which hop by two-state dynamics at 295 K. Independent of surface preparation, these clusters have an average diameter of ~5 atoms. Given prior results for metallic glasses, we suggest that this cluster size is a universal feature. The hopping activation free energy of 0.93 ± 0.15 eV is rather small, in agreement with a previously untested surface glass model. Hydrogenation quenches the two-state dynamics, apparently by increasing surface crystallinity.
Biochemistry | Chemistry