AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Thursday Sessions
       Session NS-ThP

Paper NS-ThP15
Annealing Atmosphere and Electron Irradiation Effects on Gold Nanocrystals Buried in MgO

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Nanometer-Scale Science and Technology Division Poster Session
Presenter: A. Ueda, Fisk University
Authors: A. Ueda, Fisk University
R. Mu, Fisk University
M.H. Wu, Fisk University
D.O. Henderson, Fisk University
R.M. Uribe, Kent State University
A.F. Hepp, NASA Lewis Research Center
E.M. Gordon, NASA Lewis Research Center
C.W. White, Oak Ridge National Laboratory
J. Budai, Oak Ridge National Laboratory
A. Meldrum, Oak Ridge National Laboratory
R.A. Zuhr, Oak Ridge National Laboratory
P. Wang, University of Texas, El Paso
Correspondent: Click to Email
We have reported previously annealing effects on the surface plasmon (SP) of gold nanocrystals (NCs) formed by Au ion implantation in MgO. Annealing the samples after implantation promotes the diffusion of gold atoms, nucleation and growth of the NCs. The SP absorption for the Au/MgO system annealed in an oxidizing atmosphere (OA) is observed at ~560 nm, while annealing the same sample in a reducing atmosphere (RA) shifts the SP to ~524 nm. The process is entirely reversible. We propose that the SP shift originates from the creation of F@sub n@-centers when the samples are annealed in a RA, while they are annihilated in an OA. The F@sub n@ center acts as an e@super -@donor to the Au NCs that causes a blue shift of the SP. Subsequent annealing in an OA annihilates the F@sub n@ centers and the SP shifts back to 560 nm. TEM studies on Au NCs in MgO indicate the crystals are cubic and are aligned along the <100> direction of the MgO lattice. Maxwell-Garnet effective medium theory was used to simulate the absorption spectra of the Au NCs formed in MgO under RA and OA. A good fit was obtained for sample annealed in an OA, but the fit for the annealed sample in a RA deviated from the experimental results. This is attributed to a change in the dielectric function of the Au NC that was caused by electron transfer from the F@sub n@ center. Electron beam irradiation of the Au/MgO samples was also investigated as an alternative method to study F@sub n@center creation and their interaction with the gold NCs. The optical spectra in the SP region are presented for the electron irradiated Au/MgO samples and are compared to those annealed in a reducing atmosphere.