AVS 52nd International Symposium
    Surface Science Thursday Sessions
       Session SS3-ThM

Paper SS3-ThM8
Unoccupied Electronic Structure and CO Adsorption in Ni/Cu(100) System

Thursday, November 3, 2005, 10:40 am, Room 203

Session: Reactivity of Bimetallic Surfaces
Presenter: H. Yao, Rutgers University
Authors: H. Yao, Rutgers University
S. Rangan, Rutgers University
A.G. Danese, Rutgers University
R.A. Bartynski, Rutgers University
Correspondent: Click to Email
Ultrathin (i.e. several monolayers thick) metal films in the nanometer thickness range exhibit quantum size effects in their electronic structure. These effects often lead to interesting magnetic, optical or chemical properties. The particular materials selected in our work here Ni/Cu(100) system are motivated by two main reasons: First, because its applications in spin valve structures; second, we would expect that the study of this system will help us to understand the anomalous downward dispersion of unoccupied states in Cu/Ni/Cu(100) systems. We performed a series of inverse photoemission (IPE) studies of the unoccupied electronic structure of the Ni/Cu(100) and CO/Ni/Cu(100) systems as a function of Ni thickness. IPE spectra from Ni films exhibit very rich structures. A phase accumulation model (PAM) calculation suggests only one of the three main features is consistent with metallic quantum well (MQW) State in Ni film. CO adsorption strongly modifies the spectrum by dramatically suppressing one of the main features indicating that this feature is a Ni surface resonance. Furthermore, by comparing spectra from Ni/Cu(100) with results from Cu/Ni/Cu(100), we suggest the third feature is a state confined to the Ni/Cu interface, and the Cu/Ni interface state plays key roles in the anomalous dispersion of the unoccupied states in the Cu/Ni/Cu (100) system. The correlation between chemisorption properties of Ni films of different thickness and their electronic structures are studied with Temperature Programmed Desorption (TPD) and IPE. First principles calculations illustrating the evolution of the electronic structure of Ni/Cu structures as a function of both Ni and Cu film thickness will also be presented and compared to the experimental measurements.