Speaker
Sjoerd Roorda
(Université de Montréal)
Description
Hyperuniform point patterns are characterized by a local variance that grows only as the surface area (rather than the volume) as the system gets larger and therefore do not possess infinite-wavelength fluctuations [F. Torquato & F.H. Stillinger, Phys. Rev. E **68**, 041113 (2003)]. Equivalently, it can be stated that for hyperuniform materials, the structure factor tends to zero for very small scattering vectors : S(q→0) = 0. It has been conjectured that pure amorphous silicon, a fully disordered and nearly-four fold coordinated solid, is nearly fully hyperuniform [M. Florescu *et al*., PNAS **106**, 20658 (2009)]. However this suggestion has been contested, based on a large structure factor at small scattering vectors deduced from a computer model of amorphous silicon [A.M.R. de Graff & M.F. Thorpe, Acta Crystallogr. A **66**, 22–31 (2010)]. We have undertaken measurements of the structure factor of pure amorphous silicon, made by ion implantation, at the Argonne Advanced Photon Source. The experimentally determined structure factor is much smaller than the value deduced from the model, and thus we conclude that pure amorphous silicon is nearly hyperuniform [R. Xie *et al.*, PNAS **110**, 13250 (2013)].
Primary author
Sjoerd Roorda
(Université de Montréal)
