Surface Composition and Electronic Structure of Colloidal CdSe and PbSe Nanocrystals Probed by Positron Annihilation

When: Wednesday, January 23, 2013 at 12:00 pm
Where: DA 114
Speaker: Dr. Bernardo Barbiellini
Organization: Northeastern University
Sponsor: Introduction to Physics Research

Examining surfaces at the nano-scale is one of the most challenging problems of modern materials science. We have devised an efficient way to probe the surface of CdSe and PbSe nanocrystals using positrons. A slow positron can be trapped at a surface and then annihilates. One can analyze the distribution of photons that are caused by this annihilation to gain unique surface information about the surface of the nanocrystals. An important aspect of this effort is the elaboration of a reliable theory to better understand the behavior of positrons and electrons at surfaces. A deep understanding of the positron sticking at surfaces its full exploitation will require a proper modeling of the correlated electron and positron wave function.