AVS 53rd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuM

Paper EM-TuM12
X-ray Excited Optical Luminescence Studies of ZnO Nanowires and ZnO/Mg@sub x@Zn@sub (1-x)@O Core-Shell Nanowires*

Tuesday, November 14, 2006, 11:40 am, Room 2003

Session: Zinc Oxide
Presenter: R.A. Rosenberg, Argonne National Laboratory
Authors: R.A. Rosenberg, Argonne National Laboratory
G.K. Shenoy, Argonne National Laboratory
L.-C. Tien, University of Florida
D.P. Norton, University of Florida
S.J. Pearton, University of Florida
X.H. Sun, University of Western Ontario, Canada
T.K. Sham, University of Western Ontario, Canada
Correspondent: Click to Email
As nanostructures become more complex having additional tools to unravel their optical properties will become more valuable. Due to their inherent asymmetry, the orientation of a nanowire will strongly influence its optical absorption and emission properties. In this talk we show how core-level, x-ray-excited optical luminescence (XEOL) using tunable x-rays from a synchrotron light source can be used to understand luminescence anisotropy in a disordered array of ZnO nanostructures. Optical luminescence yields from ZnO nanostructures at the Zn L and O K edges for both the band edge (~380 nm) and defect (~510 nm) peaks will be presented. At the Zn L edge the yields of both peaks are proportional to the x-ray absorption spectrum (XAS) of the wire. However, at the O K edge, marked contrasts are observed between wire XAS and the luminescence yields. There is a distinct enhancement of the yield for the band edge luminescence following 1s to 2p@sub z@ excitation relative to 1s to 2p@sub x,y@ absorption. For the defect peak excitation dramatic differences are seen between the XEOL yield and XAS of the wire. We will discuss these results in terms of the polarization of the excited electronic states and the nature of the defect states involved in the luminescence. In addition we will present recent results of a XEOL study on nanowires with a wurtzite ZnO core surrounded by a sheath composed of cubic Mg@sub x@Zn@sub (1-x)@O. The ZnO band edge luminescence (~370 nm) is blue shifted relative to the unsheathed nanowire. We also detect a deep UV peak at ~270 nm. By determining the yields of these peaks following excitation of the O K, Zn L, and Mg K core levels we are able to determine both the atomic origin and symmetry of the sites responsible for these peaks. @FootnoteText@ *This work was performed at the Advanced Photon Source and was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. W-31-109-ENG-38.