Connection One Seminar
Physics of silver in Ge2Se3:
The role of electron self-trapping
When: Wednesday, September 19, 2012
Where: GWC 487, Time: 12:00 pm – 1:00 (pizza and drinks will be served)
Speaker: Dr. Arthur Edwards – Sr. Research Physicist, AFRL – Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, NM
Abstract: Ge2Se3:Ag is an important material system in emerging memristor-based, reconfigurable electronics technologies. It is well known that Ag+1 can be introduced into a thin film from a metallic source by applying a positive bias to the silver-side of a two terminal device. Ag+1 ions are highly mobile and electroplate at the cathode. Columns of metallic material traverse the film setting up high-conductivity paths. We report density functional calculations on supercells and finite clusters based on a crystalline model of Ge2Se3 and on the incorporation of Sn and Ag into this model in both substitutional and interstitial sites. The calculations on pure Ge2Se3 show that electrons self-trap, preferentially in pairs, and that this self-trapping leads to either bond weakening (Ge-Ge and Ge-Se), for single self-trapped electrons (STE’s), or Ge-Ge bond weakening and Ge-Se bond scission, for paired STE’s. Using transition state theory, we have calculated the barrier to hopping for both the single and paired STE’s. The calculated values are 0.26 eV and 0.6 eV , respectively. The physics of interstitial defects is driven by STE’s. I will discuss how these results influence the physics of Ag incorporation for both photo-doping and bias-induced doping.
Biography: Dr. Edwards did his undergraduate and graduate study at Lehigh University. He has worked in industry, at Westinghouse Advanced Technology Laboratory, in academia, at UNC-Charlotte, and in government, at both ARL and AFRL. His current research interests include the physics of memristive systems, and continued study of defects in electronics materials.
For specific questions or comments, please contact: Margie Margie.Creedon@asu.edu
Co-sponsored by the IEEE Solid State Circuits Society