Direct Imaging of Two-State Dynamics on the Amorphous Silicon Surface

S. Ashtekar, G. Scott, J. Lyding, and M. Gruebele

Phys. Rev. Lett. 106, 235501 – Published 10 June 2011

Abstract

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 $\sim 5$ atoms. Given prior results for metallic glasses, we suggest that this cluster size is a universal feature. The hopping activation free energy of $0.93 \pm 0.15 eV$ is rather small, in agreement with a previously untested surface glass model. Hydrogenation quenches the two-state dynamics, apparently by increasing surface crystallinity.

Received 6 February 2011

DOI:https://doi.org/10.1103/PhysRevLett.106.235501

Authors & Affiliations

S. Ashtekar^1,2, G. Scott^1,2, J. Lyding^1,3, and M. Gruebele^1,2,4

¹Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, Illinois 61801, USA
²Department of Chemistry. University of Illinois, Urbana, Illinois 61801, USA
³Department of Electrical and Computer Engineering, University of Illinois, Urbana, Illinois 61801, USA
⁴Department of Physics, University of Illinois, Urbana, Illinois 61801, USA