MSc Defense: Final Oral Examination for the Degree Master of Science of Aly Rahemtulla

Event Details

  • Date:
  • Time: 11:00 AM
  • Location: MacN 222

Thesis Title:

"Local Atomic Motifs: Visualizing the Disorder of Amorphous Germanium"

Abstract:

High Resolution x-ray diffraction experiments of amorphous germanium (a-Ge) revealed structural differences that cannot be reconciled with accepted theoretical models. An intuitive computational technique has been developed to construct 3D statistical density maps to directly resolve local atomic structure of a-   Ge. A reverse monte carlo (RMC) routine is used to compare the continuous random network (CRN) model to the experimental models of a-Ge before and after annealing. Structure in the refined models is shown to exist bimodally; as a 4-coordinated tetrahedron and a buckled 3-coordinated structure similar to germanene. These structures account for 95% of the total atoms in an approximate 5:2 ratio respectively. Strong radial ordering in the second shell coupled with distortions from the perfect tetrahedron, along with variations of dihedral ordering are shown to account for the ordering present near the second correlation shell.

Examination Committee:

  • Dr. Xiaorong Qin, Chair
  • Dr. Stefan Kycia, Advisor
  • Dr. Bruno Tomberli, Advisor
  • Dr. Martin Williams