Geometric and Electronic Structures of PgAg(100) Surface Alloys Using Wiggler Radiation
Ag-Pd bulk alloys have attracted much attention due to the unusual Core Level Shifts (CLS) observed in Ag and Pd with alloy composition. CLS of both alloy components show remarkably the same sign in contradiction to the expectations of the potential model for core electron energies [1]. CLS of both Ag and Pd are in good agreement with the complete screening calculation. Interestingly, there is a change of sign in Pd CLS whereas no such change of sign observed in Ag CLS. It is interesting to study the CLS in ordered surface alloys as peak positions and thus the CLS are better determined on ordered alloys due to the sharp core levels observed compared to the random alloys. We have prepared ordered surface alloys using e-beam technique in situ in the preparation chamber of the THE-XPS machine at HASYLAB, Hamburg, Germany. CLS were calculated from the high energy photoemission data and the degree of order and the Pd adsorption site were determined by NIXSW technique. Our results showed similar sign for both Ag and Pd CLS and surprisingly, there is no change of sign in Pd CLS with alloy composition. 1. I. A. Avrikosov et.al, Phys. Rev. Lett, 87, 176403 (2001)
07/07/2006 at 3:00 pm
Dr. Jhasaketan Nayak, Tokyo, Japan
Experimental Condensed Matter Physics Group Seminar
With an aim to produce a low cost luminescent material suitable for white light emitting application, we attempted the enhancement of the visible luminescence from ZnO nanostructure. We synthesized various kind of Zno nanostructures and studied their photoluminescence properties. The nanometer size dot like structure showed brightest photoluminescence centered about yellow region of the visible spectrum. In order to enhance the luminescence further, we tried to co-dope the ZnO nanoparticles by Al and Li by a low cost, chemical co-precipitation method. Because of possible co-doping, the visible luminescence broadens and looks yellowish white, the luminescence intensity being comparable to the commercial yellow phosphor. The mechanism of the above yellowish white luminescence has not been understood. Preliminary characterization indicates a possible radiative transition associated with DAP recombination.
