PACCHIONI , Gianfranco

When imaged by scanning tunneling microscopy (STM) at constant current under nontopographic conditions, nanosized MgO islands grown on Ag(100) may show a fractal dark internal structure and/or appear embedded in the surface. On the contrary, when imaged under topographic conditions, the same islands appear as nearly flat plateaus. Islands...

We report ab initio configuration interaction calculations on the optical transitions of the E′ center, a hole trapped at an oxygen vacancy, ( - O)3Si• +(O - )3, in silica. We found two competing excitation mechanisms: (1) promotion of one electron from an O(2p) valence band orbital to the singly occupied Si dangling bond; (2) charge transfer...